Aaron Shugar, SUNY - Buffalo State
Stavroula Golfomitsou, UCL Qatar
Chandra Reedy, Univ of Delaware
Pamela Vandiver, Univ of Arizona
Society for Archaeological Sciences, XGLab and nSynergies
TC3.1: Advancements in the Analysis of Metal Artifacts
Tuesday PM, November 29, 2016
Hynes, Level 3, Room 303
9:15 AM - *TC3.1.01
On the Controversy Concerning Ancient Chinese Bronze Casting Methods
Michael Notis 1 , DongNing Wang 1
1 Lehigh University Bethlehem United StatesShow Abstract
The history of the manufacture of the magnificent bronze castings produced in ancient China has been reinterpreted a number of times during the past hundred years or so. These bronzes were first believed to be fabricated by lost wax (cire perdue) casting, but this gave way to a belief that piece mold casting was the dominant, if note the sole, method of manufacture from the Shang (1700-1100 BCE) until possibly as late as the Tang dynasty (618-907 CE). This has been reinforced by the finding, a number of years ago, of the Houma piece mold foundry, as well a number of more recent similar finds. However, this stance was challenged by the discovery in the late 1970s of intricately cast openwork bronze objects at the Tomb of the Marquis of Yi, dated to the Warring States Period (475-221 BCE). Many other questioned bronze objects have now been found since this time. An overview describing these recent object finds, along with casting experiments and related computer modeling, and x-ray studies, will be presented with the view of discerning the critical aspects of casting needed to resolve these issues.
9:45 AM - TC3.1.02
Production of Ceramic Bronze-Casting Molds in China, c. 1100-771 BCE—Firing Temperature Estimation Using FTIR
Matthew Chastain 1 , Jianli Chen 2 , Xingshan Lei 2
1 Massachusetts Institute of Technology Cambridge United States, 2 Peking University Beijing ChinaShow Abstract
The extremely high quality of bronze casting in China during the Shang and Zhou periods (c. 1600 – 221 BCE) owes to an unprecedented sophistication in the use of ceramic materials in the bronze foundry. During this period, bronze-casting molds were made from a porous, silica-rich ceramic paste that appears to have been engineered specifically for use in metallurgy. Despite this ceramic material’s essential role in ancient China’s bronze-making tradition, basic questions related to its production method and engineering properties remain unanswered.
Ceramic bronze-casting molds excavated from the Zhouyuan area of Shaanxi province, China, and dating primarily to the Western Zhou period (c. 1050-771 BCE) were analyzed using Fourier-transform infrared spectroscopy (FTIR). The molds’ firing temperatures were estimated by comparison of their FTIR spectra to those of lab-fired soil samples. These results contribute a critical piece to a broader research effort seeking a step-by-step reconstruction of molds’ production process and an understanding of the technical choices represented by that process. Results also inform a comparison of bronze-casting practice among three Zhouyuan-area foundry sites.
10:00 AM - TC3.1.03
Processing Techniques of Several Chinese Ancient Bronzes from Materials' Perspective
Chunxu Pan 1 2 , Lingmin Liao 1 3 , Yang Li 1 4 2
1 Physics and Technology Wuhan University Wuhan China, 2 Center for Archaeometry Wuhan University Wuhan China, 3 Materials and Structural Department Changjiang River Scientific Research Institute Wuhan China, 4 School of History Wuhan University Wuhan ChinaShow Abstract
1) Manufacturing techniques of armor strips excavated from the Emperor Qin Shi Huang’s mausoleum, China
The chemical compositions and microstructures of the armor strips excavated from the Emperor Qin Shi Huang’s mausoleum were examined systematically by using optical microscopy and electron microscopy. It was found that the armor strips were made of pure copper. Based on the morphology of α-Cu recrystal grain and copper sulphide (Cu2S) inclusions in the armor strips, the manufacturing techniques were proposed as follows: smelting pure copper, casting a lamellar plate, forming the cast ingots into sheets through repeated cold forging combined with annealing heat treatment, and finally cutting the sheets into filaments. Furthermore, through the deformation of copper sulphide (Cu2S) inclusions in the strips, the work rate during forging was evaluated and calculated to be close to 75%.
2) Techniques employed in making ancient thin-walled bronze vessels unearthed in Hubei Province, China
In this work, two ancient thin-walled bronze vessels unearthed in Anlu County of Hubei Province, China, were studied systematically by using optical microscopy (OM), scanning electron microscope (SEM), energy dispersive spectrometer (EDS), electron backscatter diffraction (EBSD) and nanoindentation system, and also we calculated the Sn diffusion in a Cu substrate based upon the substitutional mechanism at high temperature. The results indicated that the vessels were possibly fabricated using the following processes: (1) alloying the high-tin Cu–Sn bronze; (2) casting the preliminary shape of the vessels; (3) forging the vessels in the temperature range of 586–798 °C; (4) simply wiping tinning on the surface of the vessel at high temperature; (5) quenching the vessels to room temperature; and (6) at last, grinding and polishing the surface of the vessels. It seems that the present thin-walled bronze vessels provide an evidence of the spread of thin-walled high-tin bronze technology in China and its surrounding regions.
3) The Use of Metal Lead (Pb) in Chinese Ancient Bronzes
It has been known that the ancient Chinese technicians have fully realized the effect of element Sn in bronzes which has been recorded in a document named “Kao Gong Ji - Liu Qi” written during the Spring-Autumn Warring States Period (770 B.C. - 221 B.C.), China. However, there is no record for adding metallic lead (Pb) in the bronzes in this book. Up to now, there are still different viewpoints about the function of metallic Pb in the ancient bronzes. In this work, various ancient Chinese bronzes made in the Spring-Autumn Warring States Period were examined systematically and comprehensively. When the existence of Pb in different bronzes was summarized in group, we try to further give some explanations about the reasons for adding Pb and how Pb was added in the bronzes from the physics and materials science viewpoints.
10:15 AM - TC3.1.04
Study on the High-Tin Bronzes in Chu Culture
Yang Li 1 2 , Ran Wang 1 2 , Chunxu Pan 2 3
1 School of History Wuhan University Wuhan China, 2 Center for Archaeometry Wuhan University Wuhan China, 3 School of Physics and Technology Wuhan University Wuhan ChinaShow Abstract
The Chu Culture is one of the most important parts of the Chinese Culture. In the Spring and Autumn Period (770-475 BC) and the Warring States Period (475-221 BC), the impact of the Chu Culture on South China cannot be underestimated. There were thousands of ancient bronze artifacts with exquisite modeling, fine style, and superb skill have been unearthed in the area of Chu Culture. In the recent decades, many researches have focused on these bronzes by using new analysis techniques. Especially, high-tin bronze is one of the most important research aspects in Chu Culture’s bronzes, as it could provide scientific proof for understanding the technological level of bronze fabricating craft in Chu Culture.
In this paper, the high-tin bronzes in Chu Culture were studied systematically by using optical microscopy, scanning electron microscope, energy dispersive spectrometer, and nanoindentation. The results indicated that: (1) The fabricating techniques of high-tin bronzes in Chu Culture included integral casting, separate casting, hot forging, cold working, quenching and tempering; (2) In Chu Culture, the high-tin bronze early appeared in late Spring and Autumn Period, and became popular in Warring States Period; (3) It is a fact that the bronze fabricating craft in Chu have mastered the key to improve the mechanical properties of bronzes, i.e. using the high-tin bronze, choosing the best fabricating techniques; (4) There may be a technological communication of high-tin bronze between Chu Culture and Wu Culture in In the Spring and Autumn Period and the Warring States Period.
10:30 AM - TC3.1.05
Cu-Sn-Pb Alloy Fabricated by Powder Metallurgy and Its Application for Standard Curve Establishment of Portable X-Ray Fluorescence Instrument for Alloy Analysis on Bronze Relics
Dongsheng Wen 1 , Ya Xiao 1 2 , Guangyi Yao 1 , Weiqiang Zhou 3 , Yan Qi 3 , Shaojun Liu 1 4
1 Powder Metallurgy Research Institute Central South University Changsha China, 2 Cultural Relics and Archaeology Institute of Hunan Changsha China, 3 Shanxi Provincial Institute of Cultural Heritage Xi'an China, 4 Research Center for Chinese Village Culture Central South University Changsha ChinaShow Abstract
Bronze is one of the most metallic alloys for fabricating artifacts in ancient China. Tin and lead are used to increase the hardness and pourability of bronze, respectively. To get full information of metallurgy technology, processing, and origin of bronze it is essential to know composition and structure of the original bronze. However, during the handling of bronzes relics, only very small sample can be taken or measurements should be done on the object without sampling. One of the most often used non-destructive methods for elemental analysis is portable X-ray fluorescence (XRF). However, the measurement of portable XRF depends heavily on its standard curve line which can vary greatly. Especially, bronze artifacts are usually very heterogeneous in composition due to the segregation of lead, which it is very hard to be eliminated by annealing treatment. In this work, Cu-Sn-Pb alloy with highly homogenous composition and microstructure was successfully fabricated by powder metallurgy and the suitability of its application for establishing standard curve of portable XRF for alloy analysis on bronze relics was investigated. The samples were initially precisely characterized using reliable laboratory methods, including SEM (Scanning Electron Microscopy), ICP-AES (Inductively Coupled Plasma-atomic emission spectrometer), and SIMS (Secondary Ion Mass Spectrometry). It has been shown that the established standard curve of portable XRF can be reliable to carry out quantitative on-site elemental measurements on low corroded bronze relics.
10:45 AM - TC3.1.06
Platinum Metallurgy Before Current Era—Materials Science Evidence from Pre-Hispanic Platinum-Silver Nose Ring of the Tumaco-La Tolita Culture
Nohora Bustamante 2 1 , Ji Kim 1 , Juan Nino 1 , Jairo Escobar 2
2 Mechanical Engineering Universidad de los Andes Bogotá Colombia, 1 Materials Science and Engineering University of Florida Gainesville United StatesShow Abstract
The geographical region extending from current day southwestern Colombia to northern Ecuador was the setting for a rich history of pre-Hispanic utilization of metals with an abundant collection of nearly 38,000 metallic archaeological objects displayed and stored in more than 30 museums around the world. Here we present a remarkable object from one of these collections, a platinum-silver nose ring created by the Tumaco-La Tolita people between 350 B.C. – 350 A.C., which is currently on display at the Gold Museum in Colombia (ID: 029338). Through non-destructive materials science and engineering methods, we show that this artifact is of exceptional archaeological and metallurgical significance because it represents the first instance of a platinum-silver artifact in the history of metals. Moreover, the significance is further appreciated and contextualized when considering that, before these artifacts were studied, the earliest record of the use of platinum based objects was from Europe in the 1800s and that the development of modern platinum metallurgy only took place in the 19th century.
While it is of great importance and interest to scientifically study ‘archaeo-metallurgical’ artifacts like this nose ring, the process can be challenging due to the crucial importance of preserving these ancient objects. Non-destructive materials characterization techniques combined with reverse engineering methods are uniquely posed to analyze and reconstruct the composition, microstructure and processing steps of archaeological artifacts, and are invaluable in assessing their engineering and technological significance within the world’s cultural heritage. In this work, the physical, chemical, structural and microstructural characteristics of the nose ring were established using 3D modelling along with X-ray fluorescence (XRF), X-ray diffraction (XRD), scanning electron microscopy (SEM), and energy dispersive spectroscopy (EDS). Furthermore, based on the analysis of the characterization data and reverse engineering methods, possible processing steps for the nose ring manufacturing were proposed. Proxy objects were then reconstructed following these steps and the processing variables optimized by comparing the chemical, physical, and microstructural characteristics of the replicates with those of the original artifact. We show that this comprehensive approach to studying the nose ring gives unique cues to the advanced state of the metallurgical practices and the art of jewelry making amongst the Tumaco-La Tolita people. This work contributes towards a broader understanding of the history of platinum-silver metal working in pre-Hispanic South America.
We would like to express our gratitude to the Gold Museum of the Banco de la República in Colombia for providing this object for study.
TC3.2: Analysis, Replication and Standards to Understand Processes of Making Art Objects I
Tuesday PM, November 29, 2016
Hynes, Level 3, Room 303
11:30 AM - TC3.2.01
Synthesis of Historical Azo Pigments—Challenge and Opportunity
Joseph Lomax 1 , Suzanne Lomax 2
1 U.S. Naval Academy Annapolis United States, 2 Scientific Research National Gallery of Art Washington United StatesShow Abstract
Since 1880 when von Gallois and Ullrich synthesized the first azo-dye, Para Red (PR1), many organic azo-containing pigments have been made. Though many are still commercially manufactured, some have been manufactured and then subsequently removed from manufacture. These are referred to as “historical pigments” and many have limited or no modern analytical data. Thus if they are found, for example in artwork, it would be difficult if not impossible to identify them. Without their identity, the art history of the object would be less comprehensive and deep, and display and conservation decisions would be less informed. With their identity, a specific time range of pigment use can be inferred. We have investigated the literature and have targeted a series of historical Napthol AS, Hansa (Arylide) Yellow and Diarylide Yellow pigments. Synthesis from commercially available chemicals, including using a microfluidic flow reactor, will be described. Analysis of the product pigments by FT-IR, Raman, and mass spectrometry (GC/MS, MALDI) will be presented as appropriate.
11:45 AM - TC3.2.02
Preparation of Synthetic Indian Yellow
Katherine Spendel 1 , M. Scott Goodman 1 , Rebecca Ploeger 1 , Aaron Shugar 1
1 State University of New York College at Buffalo Buffalo United StatesShow Abstract
Indian Yellow is a historic pigment that was phased out around 1908 by the Indian government due to the inhuman means of production. It is reported to be obtained from the urine of cows that were fed exclusively mango leaves and water. Indian yellow is a yellow-orange pigment composed of the magnesium salt of euxanthic acid, and fluoresces under ultraviolet light. The manufacture of a synthetic version of Indian Yellow has been difficult due to the relative unreactivity of the two main constituents that form euxanthic acid: euxanthone and glucuronic acid. A new methodology was designed to attach surrogate groups to euxanthone, and to generate a magnesium salt to obtain a pigment with similar spectral properties as authentic Indian Yellow. In this methodology, the red dibasic form of euxanthone is generated in dimethyl formamide using potassium carbonate. One of the deprotonated oxygens on the euxanthone is then allowed to react with the surrogate group, ethyl 4-bromobutyrate. Column chromatography is then used to purify the reaction product, followed by saponification of the ester. In a similar fashion, the methylated euxanthone was also synthesized. The magnesium salts of the two new pigments were formed by maintaining the compounds under basic conditions in contact with a source of magnesium. The resulting yellow pigments were vacuum filtered and dried. The surrogate Indian Yellow pigments were analyzed with optical microscopy, FTIR, and Raman spectroscopy. The surrogate synthetic Indian Yellow pigments share similar fluorescence characteristics, microscopic structures, and spectral signatures as authentic Indian Yellow.
12:00 PM - TC3.2.03
Correlative Chemical and Structural Analysis of Microsampled Cadmium Yellow Paint from Edvard Munch’s The Scream (c.1910, The Munch Museet) in Scanning Transmission Electron Microscopy
Barnaby Levin 1 , Kayla Nguyen 1 , Megan Holtz 1 , Marcie Wiggins 2 , Malcolm Thomas 1 , Jennifer Mass 2 3 , Adam Finnefrock 5 , Robert Opila 2 , Thomas Beebe 2 , Eva Tveit 4 , David Muller 1
1 Cornell University Ithaca United States, 2 University of Delaware Newark United States, 3 Rijksmuseum Amsterdam Netherlands, 5 Scientific Analysis of Fine Art, LLC Philadelphia United States, 4 Munch Museum Oslo NorwayShow Abstract
Cadmium sulfide (CdS) based yellow pigments in early modernist art masterpieces from the late 1800s and early 1900s, such as Edvard Munch’s The Scream are undergoing fading, flaking, and discoloration as they age. Characterization of the CdS and cadmium carbonate (CdCO3) distribution within cadmium yellow paint from The Scream, is crucial for understanding degradation of the CdS pigment, and the role of CdCO3 and other compounds in paint synthesis and photo-aging.
Correlative spectroscopic and crystallographic analysis of focused ion beam (FIB) milled paint samples in scanning transmission electron microscopy (STEM) offers site-specific, sub-nanometer resolution of paint microstructure and chemical composition.
Here, we present a STEM analysis of a microscopic FIB sample of cadmium yellow paint from The Scream. The FIB sample, measuring ~ 7 µm x 6 μm x 100 nm was extracted from a microsample of flaking yellow paint, from the region in the water adjacent to the two background figures on the bridge in the painting.
Spectroscopic mapping of the FIB sample by x-ray energy dispersive spectroscopy (XEDS) in STEM revealed the paint to be primarily composed of ~ 1 µm sized CdCO3 and cadmium chloride particles, intermixed with smaller, ~ 100 nm sized CdS, CdCO3, and cadmium chloride particles. Principal component analysis of the XEDS data indicated that the sulfur, oxygen, and chlorine XEDS signals were spatially separated, suggesting little to no sulfates or chlorates were present. This is significant because cadmium sulfates are observed in contemporary photo-degraded works by Henri Matisse and Vincent Van Gogh, and its absence supports the hypothesis that in The Scream (c. 1910), CdCO3 is present in yellow paint as a residual starting reagent from CdS synthesis. The observation of large CdCO3 particles also supports this hypothesis. The role and origin of the chloride is not yet fully understood, but its detection is significant, as the presence of chloride in cadmium yellow paint can result in increased reactivity/photosensitivity of the CdS pigment.
A 4-dimensional crystallographic dataset, consisting of diffraction patterns recorded in under 1 ms at each pixel of a series of 256x256 pixel scans of the sample, was acquired using a new high-speed pixel array detector with single electron sensitivity, and a dynamic range of 1 to 106 electrons. Mapping variations in the center of mass of the diffraction patterns allowed us to visualize the crystal orientation of the particles in the sample, revealing that many of the paint particles are polycrystalline, with grain sizes of 10s to 100s of nanometers. Cubic CdS and hexagonal CdCO3 were identified from individual diffraction patterns in the dataset.
Further analysis of our data promises new insights into the relationship between pigment synthesis and photo-aging, and crystal grain size and structure. This will be critical in assisting with the preservation of these iconic paintings.
12:15 PM - TC3.2.04
Degradation of Cd-Yellow Pigment—An Ab Initio Study of Defects and Adsorption of Oxygen and Water on CdS
Laura Giacopetti 1 , Alessandra Satta 1
1 CNR-IOM Cagliari Monserrato ItalyShow Abstract
The cadmium yellow paints used in impressionist and modernist paintings in early 1900s are undergoing several deterioration processes, including whitening and discoloration. Relevant effects produced at the surface of modern paintings include the growth of discolored crusts, formed mainly by white globular hydrated cadmium sulfate CdSO4*nH2O and cadmium carbonate (CdCO3). In view of the fact that the pigment, cadmium sulfide, was historically synthesized by means of dry and wet processes and that CdCO3 and CdSO4 are reagents for this procedure, their identification alone does not constitute conclusive proof of photo-oxidation. The origins of such chemical and physical alterations are still under debate. Structural defects in CdS, among other possible causes like photo-oxidation processes, may play a role in the degradation process. Their presence in the pigment surface alters the electronic structure of cadmium sulfide by forming acceptor levels in the gap of the semiconductor. Such levels make the surface more reactive in the interaction with external agents (oxygen, water …). To this end, we present a theoretical study of points defects, namely Cd- and S- vacancies, in the structural wurtzite structure (bulk) and [10-10] CdS surface. In order to understand, at atomic level, the oxidation and hydration mechanisms of these whitish globules, we present the early stages of the interaction between the hexagonal clean and defective [10-10] surface of CdS and O2 and H2O molecules to simulate the combined effects of exposure to air and humidity. The geometrical and electronic structures as well as the vacancy formation and adsorption energies are determined with the use of a first principles method. All the calculations are performed within the framework of the Density Functional Theory (DFT) in the Generalized Gradient Approximation (GGA-PBE) with the use of ultrasoft pseudopotentials. A formalism based on defects formation energies allowed us to calculate thermodynamic and optical transition levels associated with trap states in the band gap. This work highlights the role that first-principles methods can play in the application of materials science to art conservation.
12:30 PM - TC3.2.05
Shades of Yellow—Investigation of Late 19th- Early 20th-Century Yellow Artists’ Pigments from the Studios of Henri Toulouse-Lautrec and Edvard Munch
Aaron Shugar 1 , Jennifer Mass 6 , Rebecca Ploeger 1 , Marcie Wiggins 3 , Thomas Beebe 3 , Karl Booksh 3 , Alyssa Hull 2 , Robert Opila 9 , Terje Syversen 8 , Eva Tveit 8 , Letizia Monico 7 , Koen Janssens 4 , Costanza Miliani 5 , Jocelyn Alcantara-Garcia 3
1 Art Conservation Buffalo State College Buffalo United States, 6 Department of Conservation Rijksmuseum Amsterdam Netherlands, 3 Department of Chemistry and Biochemistry University of Delaware Wilmington United States, 2 Department of Chemistry Duke University Durham United States, 9 Materials Science and Engineering University of Delaware Wilmington United States, 8 Munch Museet Oslo Norway, 7 Department of Chemistry University of Perugia Perugia Italy, 4 Department of Chemistry University of Antwerp Antwerp Belgium, 5 Italian National Research Council Rome ItalyShow Abstract
Samples from metal artist pigment tubes were collected from both the estates of Henri Tolouse-Lautrec and of Edvard Munch. The Tolouse-Lautrec paints were all closed, while several of the Edvard Munch paints were uncapped and showed signs of oxidation at the tube opening. The range of samples collected include several compositions and shades of yellow pigments, including chrome yellow, cadmium yellow, Naples yellow, and even a sample of thallium chromate yellow. Brands from Toulouse-Lautrec include Dubus and Berville. Brands from Munch’s collection include the Ambor, Arnbak, Blockx Fils, Devoe and Raynolds, Gunther Wagner, Herman Neisch, Herbolaget Wilh., Lefranc, Vilh. Pacht, and Winsor and Newton brands. XPS and XANES analysis of the Munch pigments showed the presence of different manufacturing impurities, photo-oxidation products, and deliberately added fillers. In the case of the Toulouse Lautrec pigments, having access to samples that have been sealed in their original tubes allows for the investigation of pigments with limited degradation; certainly ones that have no issues related to light degradation. This provides a unique opportunity not only to characterize the pigments, but also to look into their compositions prior to alteration and thus separate out residual synthesis materials from how the paints may deteriorate. This will provide invaluable insight into the interpretation of the altered yellow paints observed on the works by these artists, where light exposure has already occurred, along with potential photodegradation that must be separated out from paint formulation materials.
Aaron Shugar, SUNY - Buffalo State
Stavroula Golfomitsou, UCL Qatar
Chandra Reedy, Univ of Delaware
Pamela Vandiver, Univ of Arizona
Society for Archaeological Sciences, XGLab and nSynergies
TC3.3: Advanced Techniques in Imaging Technology for Art and Cultural Heritage
Wednesday AM, November 30, 2016
Hynes, Level 3, Room 303
9:00 AM - *TC3.3.01
Expanding Capabilities of Existing Spectral Imaging Technologies for Cultural Heritage
Fenella France 1
1 Preservation Research and Testing Library of Congress Washington United StatesShow Abstract
There is a tendency to jump to newer technologies rather than expanding the capabilities of existing proven imaging modalities. Spectral imaging of cultural heritage provides a non-invasive method for preserving our history and advancing preservation applications through utilization of different illumination modes, Z-plane imaging, separation of fluorescence components and advanced processing techniques. The successful transfer of spectral imaging to cultural heritage has led to applications that enable non-invasive chemical identification of historic materials, and the recovery of obscured and degraded non-visible information. Multivariate image analysis of spectral imaging data can non-invasively characterize colorants and pigments in historic documents and objects. Spectral image datasets have detected changes due to exposure of historic documents and objects to various environmental conditions, including the assessment of changes during short-term exhibits of light-sensitive materials. Spectral imaging data can also detect historic treatments of Mayan objects and has been utilized to monitor the impact of modern stabilization treatments. Along with these modes of discovery, the combination of reflectance and transmittance illumination, fluorescence response, and differentiation of treatment protocols expands preservation assessment. Spectral imaging analysis advances the capability for non-contact chemical characterization of colorants, inks, and substrates through their specific spectral response, aiding provenance of historic artefacts. The ability to track and assess the impact of treatments ensures no unwanted effects from conservation actions intending to preserve and stabilize significant objects. This can aid display decisions detection of change before these are visible to the unaided eye. Spectral imaging has the added benefit of providing a map of the response of all materials across an object, revealing overlays and non-pure end-members, as opposed to the more common single-point analysis of many other chemical analytical techniques. This mapping aspect aids complementary single-point analyses. The Library of Congress (LC) conducts spectral imaging with a customized spectral imaging system, a 51 mega-pixel Monochrome E6 Camera with integrated LED illumination panels containing 23 wavebands from ultraviolet, visible and near infrared spectral regions, capable of acquiring data for identification of a wide gamut of organic and inorganic materials. The data cube used for multivariate analysis incorporates the captured UV, visible, and NIR spectral images in reflected, transmitted, and raking illumination modes, with all images fully registered. This minimizes handling of fragile items and maximizes post-acquisition analysis. Examples will be provided for a range of historic documents; the Waldseemuller 1507 World Map, Constitution debate notes, Bartok’s final Concerto, and the assessment of modern fugitive 21st century inks.
9:30 AM - TC3.3.02
Luminescence Imaging of Paintings with a Dual Wavelength Time-Gated System
Austin Nevin 1 , Daniela Comelli 2 1 , Alessia Artesani 2 , Gianluca Valentini 2 1
1 Department of Physics Polytechnic University of Milan Milano Italy, 2 Dipartimento di Fisica Politecnico di Milano Milano ItalyShow Abstract
We will present recent advances in the analysis of paintings and pigments using a dual wavelength time-resolved imaging approach. An instrument is based on a time-gated CCD and pulsed laser excitation at 532 and 355 nm, and has been applied to the analysis of Renaissance sculptures in marble, wall paintings, Egyptian artefacts and, more recently, for the imaging of Futurist paintings. Examples of applications of Time resolved photoluminescence (TRPL) imaging will be shown both for pigments and for works of art. The analysis of pigments, which range from Egyptian Blue to Zinc Oxides and other semicondutors reveals a range of different luminescence lifetimes and decay profiles.
Heterogeneities in historical samples may be evidence of manufacturing processes and the presence of trace impurities linked to mineral extraction. The application of TRPL will be shown for the analysis of paintings containing organic lake pigments, luminescent crystals and semiconductors. A large amount of information regarding the photophysics of different materials is generated with TRPL and can provide data which can be used to discriminate pigments with the same chemical composition; analysis of historical pigments has demonstrated a range in lifetime values which may be related to different intrinsic defects and manufacturing processes. In addition investigations using TRPL of cadmium pigments demonstrates the depence of PL on the power density of excitation, a property shared with other semiconductors like Zinc Oxide.
The interpretation of data from TRPL analysis requires care and we have adopted an approach based on the use of other complementary analytical methods including Electron Paramagnetic Resonance (EPR), Scanning Electron Microscopy and X-ray Fluorescence. Advantages and disadvantages fo the technique and further avenues for reserach and development will be presented.
9:45 AM - TC3.3.03
Moisture Behaviour of PEG-Treated Archaeological Oak—The Role of a Hydrogel on a Degraded Cellular Structure Documented with Neutron Imaging
Dominique Derome 1 , Eleonora Piva 2 , David Mannes 5 , Guylaine Desmarais 3 , Eleanor Schofiled 4
1 Swiss Federal Laboratories for Materials Science and Technology Duebendorf Switzerland, 2 Portsmouth University Portsmouth United Kingdom, 5 Paul Scherrer Institute Villigen Switzerland, 3 ETH Zurich Zurich Switzerland, 4 The Mary Rose Trust Portsmouth United KingdomShow Abstract
The warship, Mary Rose, which was raised in 1982 after 437 years under the sea bed, gives a unique insight into Tudor life. To preserve this important shipwreck, archaeological wood from the shipwreck was sprayed with an aqueous solution of polyethylene glycol (PEG, first grade 200 then 2000) for 19 years in order to mechanically stabilise the remaining ship hull, and to minimise collapse and shrinkage of the wood upon drying. Once the wood consolidated, the ship is acclimatized to museum indoor conditions. Thus, in 2013, the drying of the ship was started under an environment of 19degC and 54%RH.
The structure of wood has two main scales: an anisotropic cellular structure and a nanoporous cell wall material. Over a growing season in a temperate climate, the tracheids vary from earlywood to latewood cells, resulting in a growth ring pattern. Earlywood cells possess a larger diameter, a larger lumen and thinner walls than latewood cells do. During the years under water, the ship wood polymeric components deteriorated to some extent, mainly resulting in a loss of holocellulose in the cell walls. PEG200 is used to reinforce the cell walls. In addition, the cellular and growth ring structure can still be present but most of the lumens are filled with PEG2000 as it is used to consolidate the more degraded 10 mm from the surface of a timber piece. Thus, archaeological wood has different degrees of degradation from surface inwards, which can cause different water-PEG-wood interaction mechanisms. Overall, the presence of PEG presents a clear challenge in terms of imaging with neutrons.
Monitoring the moisture content of the wood allows us to evaluate the drying process, to predict the drying rate and to understand the resulting impact of these on the mechanical properties of wood and the movement currently taking place on the ship structure due to shrinkage. To document in detail the drying process, the moisture content distribution is imaged at high temporal, spatial and hygric resolution using neutron imaging. Water sorption and desorption experiments are performed on small samples of archaeological oak wood treated with PEG200 and PEG2000 and in recent PEG-treated oak wood, under controlled conditions. Neutron radiography is based on intensity measurements of a neutron beam transmitted through an object. The high interaction of neutrons with hydrogen allows the quantification of the water present in the samples. The measurements were performed at the Neutra beamline, SINQ, Paul Scherrer Institute, CH.
To further our understanding of the material properties and behaviour of the Mary Rose hull, a complete desorption and sorption series of selected timbers are documented with neutron imaging. We present the sorption and desorption moisture content distribution, and resulting swelling/shrinkage, fields. From these, water diffusion coefficients are indirectly determined for PEG treated wood, compared with that of untreated archaeological wood.
10:00 AM - TC3.3.04
Investigating Natural Substituted Anthraquinone Red Laked Dyes with Fluorescence Lifetime Imaging Microscopy
Tana Villafana 1 2 , Ryan Beams 1 , John Delaney 2 , Stephan Stranick 1
1 Advance Measurement Laboratory Center for Neutron Research Gaithersburg United States, 2 Department of Scientific Research National Gallery of Art Washington United StatesShow Abstract
Natural substituted anthraquinone red dyes such those extracted from insects (i.e, cochineal, kermes, lac) or vegetal sources (madder root) have been used since ancient times as a pigment. These pigments are often laked to a substrate such as aluminum before use as a pigment to make polychrome art objects. They are prized for their rich color and ability to be used as glazes or in paintings on base colors such as vermilion or red lead or mixed into other pigments such as ultramarine or iron oxides. Unfortunately the non-invasive, in situ, identification of these red lakes in works of art remains challenging at best. Limited success has been achieved using far-red Raman spectroscopy, diffuse reflectance spectroscopy, and fluorescence emission spectroscopy. The former having the highest fidelity when possible and the latter can at best separate between insect or vegetable sourced red lake dyes. These limitations remain even when cross-sections are available. Surface enhanced Raman spectroscopy has shown the most progress as a universal tool but suffers from the need of micro/nano-samples and is not always successful, often for unknown reasons. Thus there remains the need for new analytical tools to help in the identification of these pigments non-invasively and in situ, especially in paint cross-sections.
In this talk we present results examining the potential utility of state of the art one and two photon fluorescence lifetime imaging microscopy (FLIM) to map and identify these red-laked pigments using fluorescence emission lifetimes with sub-micron lateral and micron axial resolution. Results of the analysis from mock paint samples of laked cochineal, kermes, lac and madder samples will be presented including the feasibility of using the spectral and temporal information to separate these pigments. Of particular interest is the relative lifetime differences of cochineal versus lac, which has been reported to have different lifetimes in paint outs. Other key questions that will be presented include the effect of light scattering on the observed fluorescence lifetime by non-dye pigments.
10:15 AM - TC3.3.05
Application of Visible and Near Infrared Diffuse Reflectance Imaging Spectroscopy and Luminescence Imaging to Identify and Map Original and Conservation Artist's Materials in a Greco-Roman Fayum Portrait
John Delaney 2 , Kathryn Dooley 2 , Giorgio Trumpy 2 , Roxanne Radpour 1 3 , Ioanna Kakoulli 1 3
2 Department of Scientific Research National Gallery of Art Washington United States, 1 Department of Materials Science and Engineering University of California, Los Angeles Los Angeles United States, 3 Molecular and Nano Archaeology Laboratory University of California Los Angeles Los Angeles United StatesShow Abstract
Diffuse reflectance imaging spectroscopy and luminescence imaging were investigated as relatively rapid analytical methods to document and identify the materials, technique and state of preservation of a Greco-Roman Fayum Portrait of the second century AD, “Portrait of a Woman”, in the collection of the National Gallery of Art. Two highly sensitive hyperspectral cameras, one operating from 400 to 950 nm and the other from 1000 to 2500 nm, both with ~3 nm spectral sampling, were used to create a hyperspectral image cube. The collection time per camera was < 10 minutes each and the complete image analysis took ~ 1 hour using semi-automatic convex hull-based multi-variant image processing. Illumination provided by LED with excitation wavelength in the blue-green was used to capture the visible luminescence. The resulting spectra of both the pigments and the paint binder were compared with spectral databases of expected materials – both historical and contemporary. Based on characteristic visible absorption and luminescence features, yellow and red earth pigments were identified along with a black colorant and madder lake, an organometallic complex. Several modern pigments associated with previous conservation treatments were also identified. Resulting maps indicated the spatial distribution of surviving original materials and determined areas associated with previous conservation treatments. The comparatively fast and precise level of documentation, including high color accuracy, suggests that combined diffuse reflectance imaging spectroscopy and luminescence imaging should be considered as ‘go to’ techniques to document artifacts of similar origin and nature.
10:30 AM - *TC3.3.06
A Novel Macro-Scanning Imaging Spectrometer System for Collection of Multi-Modal Image Cubes of Paintings and Drawings
John Delaney 1 2 , Kathryn Dooley 1 2 , Damon Conover 2 , Lisha Glinsman 1 , Koen Janssens 3 , Murry Loew 2
1 Department of Scientific Research, Division of Conservation National Gallery of Art Washington United States, 2 Department of Electrical and Computer Engineering George Washington University Washington United States, 3 Department of Chemistry University of Antwerp Antwerp BelgiumShow Abstract
Abstract Body: A multi-modal imaging scanner able to cover an area up to 1.5 by 1.5 m has been designed and constructed to provide high spatial, and spectral - resolution image cubes of works of art. The scanner has linear encoders providing micrometer positional information and can move the artwork across an array of imaging sensors in three different collection modes: raster scan, line scan, and step/stare. The three imaging modalities include optical reflectance imaging spectroscopy (RIS) from the visible to near infrared (400 nm to 2500nm, few nm sampling), fluorescence imaging spectroscopy (FIS) in the visible to near infrared using variable excitation light sources, and X-ray fluorescence imaging spectroscopy (mXRF). The first two imaging modalities provide molecular information and the third elemental information of artists’ materials. Custom software was written to register the image cubes to a reference color image and produce elemental maps from the mXRF cubes. Such multi-modal information is providing improved insights into how the paintings were constructed as well as revealing changes made by the artists, including reusing canvases of early paintings. In this paper we will show several cases studies of how the use of the various imaging modalities provides a more comprehensive understanding of a given work of art. For example, results from mXRF and RIS to investigate the reuse of a canvas by Bazille entitled “Woman with Peonies” (National Gallery Art, DC) will be presented. We have used information from RIS and FIS to examine the presence of eosin in several van Gogh paintings, including “Roses”(National Gallery Art, DC). Separately, we have conducted degradation studies on smalt to determine the change in the reflectance spectra in the visible and near infrared and correlated the reflectance “molecular” maps with those of elemental maps related to smalt for Rembrandt’s “Lucretia”, also in the collection of the National Gallery of Art, DC.
TC3.4: Characterization and Development of New Materials for Use in Conservation Treatments I
Wednesday PM, November 30, 2016
Hynes, Level 3, Room 303
11:45 AM - TC3.4.01
Material Properties and Microstructure Contributions to Vibrational Damping in Arundo Donax L—Reed Cane for Woodwind Instruments
Connor Kemp 1 2 , Gary Scavone 1 2
1 McGill University Montreal Canada, 2 Centre for Interdisciplinary Research in Music Media and Technology Montreal CanadaShow Abstract
Natural cane reeds (Latin name Arundo Donax L and here termed ADL) have been used on woodwind instruments for centuries with little change. The reed acts as a mechanical valve controlling the energy input into the musical instrument and it is the musician’s first option for altering the instrument’s sound and response characteristics. Despite this, their consistency, variable performance, durability and sensitivity to ambient conditions make it difficult for the musician to find and maintain a reed that responds to their liking. Thus it is desirable to examine the material, microstructural and anatomical properties of the reed and their contributions to vibrational performance with input from mechanical engineers, materials scientists and musicians.
In the present work raw samples of ADL obtained from a manufacturer in pre-cut form are sectioned into longitudinal and transverse specimens for mechanical characterization. Prior to testing, samples are conditioned using an incubation system to 37 degrees Celsius and 90% relative humidity, mimicking in-vivo conditions of the reed. Initial microstructure analysis of each specimen is completed using optical microscopy to quantify fiber spatial arrangement, size and the existence of micro-cracks along the fiber-matrix interface. X-ray diffraction is also used to quantify the fraction of crystalline cellulose present in each sample. Specimens are then excited over a specific frequency range similar to that of in-vivo reeds using pressure waves in a non-contact setup. Values of internal friction are obtained as logarithmic decrement values for frequency dependent decay. One set of specimens is then subjected to cyclic mechanical loading at low frequency (< 1Hz) and stresses up to 100MPa. The other set is maintained at the given environmental conditions using the incubator and aged through temperature and humidity cycling. Comparisons of post-testing microstructure damage and internal friction measurements are then completed to delineate specific degradation mechanisms due to mechanical/fatigue deterioration and moisture cycling.
It is found that interfacial degradation between the fibers and matrix is more prominent for the moisture cycled specimens while lumen distortion is present for the fatigued samples. Degradation of the matrix for moisture cycled samples is also observed through changing diffraction measurements of crystallinity. Logarithmic decrement values are found to change more significantly in the moisture cycled samples with frequency dependent losses also changing with time. It is likely that samples with less variable fiber and lumen sizes coupled with a more homogonous distribution of these structures result in smaller interfacial stresses through minimized swelling anisotropy. In order to minimize the effects of reed variability, it is suggested that reed manufacturers screen raw material prior to machining to decipher which batches of ADL contain homogenous distributions of ADL fibers.
12:00 PM - TC3.4.02
Corrosion Phenomena at and Nanoscale Anticorrosion Treatments of Pipe Organ Metallic Materials Using Ion Beam Based Methods
Bernadetta Pelic 1 , Wolfgang Skorupa 1 , Dirk Eule 2
1 Helmholtz-Zentrum Dresden-Rossendorf Dresden Germany, 2 Hermann Eule Orgelbau GmbH Bautzen GermanyShow Abstract
Historical pipe organs with their unique sound and beautiful housing are important objects of the European cultural heritage dating back to the 15th century for the oldest ones being playable yet. But new instruments are built permanently up to the present time. The instruments contain mostly a considerable number of metallic pipes (flute and reed types), which are sometimes prone to heavy corrosion attack, resulting finally in a loss of their voice. Under certain conditions, the atmospheric corrosion of reed pipe tongues as well as flute pipe foots consisting of Cu-Zn alloys (brass) and PbSn-based alloys, respectively, is strongly enhanced by traces of volatile organic compounds (especially acetic acid vapor) and other corrosive gases.
Experiments have been undertaken to explore the corrosion resistance of CuZn and PbSn-based alloys against vapour from an aqueous solution containing high acetic acid concentration (2 – 5 v/v%), by deposition of protective films of either Al2O3 or Al on the nanoscale using pulsed laser deposition (PLD) and magnetron sputtering (MS). Afterwards, in order to improve the adhesion between the deposited layer and the substrate as well as to perform a kind of nitridation of the coatings, the samples were implanted with nitrogen ions using the plasma immersion ion implantation (PI3) process.
Such a nanoscale coating (~50 nm) is then able to withstand stresses and vibrations due to sound generation in organ pipes. Moreover it produces a barrier to volatile organic acids and water vapour. The laboratory corrosion test of the applied protective treatment for lead-tin and brass samples were combined with the field work studies to approach the best conditions for the samples research in real environment. Some of the samples were exposed for 15 months in a small North-German church with a harmful (corrosive) indoor environment.
Modifying the surface of metals and thin film properties on the nanoscale using fundamental phenomena based on ion-solid interactions as well as standard conventional methods can create new technological applications in restoration and conservation to preserve our historical and modern cultural heritage.
12:15 PM - TC3.4.03
The Use of Solvent-Gel Systems for the Cleaning of PMMA
Stefani Kavda 1 , Emma Richardson 2 , Stavroula Golfomitsou 1
1 University College London, Qatar Doha Qatar, 2 University College London London United KingdomShow Abstract
Poly(methyl methacrylate) (PMMA) is one of the most commonly used plastics in art and design. The amorphous nature of PMMA allows the penetration of solvents ordinarily employed in cleaning treatments, thus leading to irreversible changes such as stress cracking and embrittlement. Additionally, its transparency makes it harder for conservators to carry out cleaning, as any sort of chemical or mechanical alteration on the surface or the bulk of the material could compromise its visual properties. Due to such issues, current cleaning practices of PMMA within the conservation profession have been approached with considerable caution. This paper discusses the use of solvent-gel systems for the cleaning of PMMA surfaces. Aqueous polymer gel systems have been introduced to conservation as a way to use liquids in a controlled and effective manner. These systems have been mostly formulated for paintings, wooden artefacts and stone. Their application on plastics is more recent. Experimental work is being carried out through a series of statistically designed experiments on new (unaged) and artificially aged PMMA samples. The experimental work consists of experiments aiming to assess the innocuousness of a variety of materials constituting the gel cleaning systems. The individual effect of the free solvents (deionized water, ethanol, isopropanol and petroleum ether), the pure gel carriers (Agar Agar, Gellan, Pemulen™ TR-2, Carbopol® EZ 2-Ethomeen® C-25, Carbopol®-TEA and 80% hydrolysed PVAc-borax) and their combinations at two different application times (5 and 60 minutes) on PMMA are assessed. Quantitative weight change measurements, qualitative visual observation with the aid of 3D stereomicroscopy and scanning electron microscope (SEM) imaging, and spectroscopic analysis with attenuated total reflectance Fourier transform infrared spectroscopy (ATR-FTIR) were used to evaluate the effect of these systems. Initial results showed that free solvents, especially ethanol and isopropanol affect the transparency of the samples. The application time for both the free solvents and the solvent-gels systems is one of the most significant factors. The longer the application, the more evident the effect they have on the surface. SEM imaging showed that most pure gels leave residues on the samples, with the two Carbopol® gels leaving the most. Pure Pemulen gels cause clouding of the surface, while Carbopol®, especially with Ethomeen®, and Pemulen™ solvent-gels also affect the transparency of the samples. SEM imaging suggests minimal scratching after solvent and gel use. The samples will be chemically assessed using FTIR. The experimental work of the aged samples is forthcoming, however, the preliminary results show that the methodology and solvent-gels used need to be developed further for applications on PMMA.
12:30 PM - TC3.4.04
Some Recent Findings on Marble Conservation by Aqueous Solutions of Diammonium Hydrogen Phosphate
Enrico Sassoni 1 2 , Gabriela Graziani 1 , Elisa Franzoni 1 , George Scherer 2
1 University of Bologna Princeton United States, 2 Princeton University Princeton United StatesShow Abstract
Marble has been used in architecture and sculpture since antiquity. The anisotropic thermal behavior of calcite grains that marble is made of, together with its very low open porosity, make marble highly sensitive to temperature variations. As a result of repeated thermal cycles, calcite grains lose cohesion and start to detach, leading to the so-called "sugaring" phenomenon. Unfortunately, at the moment no fully satisfying treatment for consolidation of sugaring marble exists. In this paper, we report some recent results on the use of an innovative phosphate-based treatment for consolidation of marble. First, artificially weathered marble samples were prepared by a novel method that produces samples with a gradient in cohesion and mechanical properties. The method is to subject marble to high temperature by putting it in contact with a hot plate for a certain time, the heating temperature and duration being determined by a mathematical model that takes into account the temperature-dependent thermal diffusivity of marble. The resulting samples exhibit more pronounced damage near the surface that was in contact with the hot plate, in a similar way as naturally weathered marble is more damaged near the external surface. Then, the efficacy of the phosphate consolidant in re-establishing cohesion in weathered marble was evaluated. The phosphate treatment is based on the idea of forming hydroxyapatite (Ca10(PO4)6(OH)2, HAP) as the reaction product between calcite grains and an aqueous solution of diammonium hydrogen phosphate ((NH4)2HPO4, DAP). To promote the formation of HAP, in this study we investigated the addition of small quantities of ethanol to the DAP solution. Thanks to the presence of ethanol, the hydration shell of calcium and phosphate ions in the DAP solution is weakened and HAP formation is promoted. The effect of consolidation is evaluated using nanoindentation on cross-sections of the untreated and treated samples. The results of the study indicate that the HAP-based consolidant is effective in restoring the mechanical properties of weathered marble and, depending on the initial level of damage, the original cohesion can be completely restored. Considering the high efficacy demonstrated in this study and the reduced alterations in marble aesthetic appearance, pore structure and thermal behavior assessed in previous studies, the phosphate treatment is confirmed as one of the most promising inorganic consolidants for the conservation of marble.
12:45 PM - TC3.4.05
Combined EDXRF and Raman Spectroscopy in a Portable Instrument for Cultural Heritage Applications
Nicholas Barbi 1 2 , Roberto Alberti 2 , Tommaso Frizzi 2
1 nSynergies Inc. Sarasota United States, 2 XGLab SRL Milan ItalyShow Abstract
XRaman is a portable spectrometer designed to perform in-situ, fast and non-destructive combined elemental and molecular analyses, with mm-scale spatial resolution, using the complementary pXRF and Raman techniques. When the 1 mm X-ray spot size is selected, Raman and X-ray information come from the precise area that is visually selected through the instrument’s high resolution internal camera. XRaman is therefore suitable to any materials application which can benefit from the combined analyses with mm-scale spatial resolution. In particular, XRaman, which does not require contact with object, was developed specifically for cultural heritage applications, including analysis of paintings, frescoes, printed or hand-written materials (documents, books, parchments and manuscripts), metals, jewels, ceramic objects, seals, glass objects, marbles and jades.
Detection Probe Design
pXRF and Raman components are tightly integrated into a compact detection head, weighing only 2.7 kg, which is mounted on a light tripod provided with the instrument. The software selectable X-Ray spot size can be 0.5, 1 or 2 mm in diameter, while the Raman excitation laser is fixed at 1 mm. When the 1 mm X-ray spot size is chosen, there is precise coincidence of the area from which the Raman and X-ray spectra are collected. The operator controls the position of the analysis spot by means of an internal camera and precise x-y movement of the head positon. The optimum stand-off of the head from the analyzed object 1 cm, controlled by moving the head toward the object until a pointing laser coincides with the axial excitation laser. Raman and X-ray spectra can then be collected sequentially from the selected area, without contacting the object.
The SDD active area is nominal 25 mm2 (optional 50 mm2) with energy resolution <140 eV on the Mn Ka peak, and uses the innovative CUBE preamplifier. A Rh target X-ray tube is standard with a 50 kV power supply, 8 W maximum. There are three software selectable spot sizes available (0.5, 1 and 2 mm) and four software selectable primary beam filters.
The excitation laser is 785 nm (532 nm or 1064 nm available). The high performance thermo-electrically cooled fiber optic spectrometer is characterized by 2048 pixels (14 mm by 200 mm) and a 3-stage thermo-electrically cooled and regulated CCD detector. Spectroscope range is 785-1100 nm (up to 3650 cm-1), Dc =±0.5nm, Line Width = 1.3 cm-1. A thermo-electric cooler is used for laser temperature control, and optical power is up to 500 mW.
The software provides combined spectra (XRF and Raman) visualization, as well as complete control of the analysis head and the image taken by the internal integrated camera. The software includes Automatic Peak ID and Fundamental Parameters for XRF and complete spectral manipulation.
TC3.5: Analysis, Replication and Standards to Understand Processes of Making Art Objects II
Wednesday PM, November 30, 2016
Hynes, Level 3, Room 303
2:30 PM - TC3.5.01
The Chemistry of Digital Fine Art Paper Yellowing—A Comparative Case Study of Moab Entrada Rag Natural 300 and Harman Inkjet Glossy Art Fibre Warmtone by Hahnemühle
Savannah Butler 1 , Carew Giberson-Chen 1 , Nina Shevzov-Zebrun 1 , Vanya Zvonar 1 , Monique Fischer 2 , Arthur Mcclelland 3
1 Chemistry and Chemical Biology Harvard University Cambridge United States, 2 Northeast Document Conservation Center Andover United States, 3 Center for Nanoscale Systems Harvard University Cambridge United StatesShow Abstract
The yellowing of inkjet papers is a documented problem for the art conservation community. This study investigated two commercially available inkjet papers that had yellowed naturally under different conditions. A double-coated fine art paper MOAB Entrada Natural 300gsm developed a yellow stain within one year of printing, after unprotected exposure to light and atmospheric pollutants in a home environment. A roll of Harman Inkjet glossy fine art fiber warm tone paper by Hahnemühle yellowed when the packaging material, a polyethylene bag, was in contact with the paper during shipping.
Scanning electron microscopy (SEM), X-Ray Photoelectron Spectroscopy (XPS), Fourier Transform Infrared Spectroscopy (FTIR), and UV-VIS reflection measurements were used to characterize the naturally yellowed papers. Attempts were also made to purposefully drive the yellowing reactions in fresh samples of these papers. Fresh paper samples were exposed separately to short wave UV light, long wave UV light, and NO2 gas (to simulate atmospheric pollution).
The SEM of the cross sectioned papers revealed a complex microstructure in the coatings of the papers. Chemical analyses suggested that neither UV exposure nor NO2 exposure was the sole reason for natural yellowing. The pattern of chemical changes from XPS line scans of cross sections of the naturally yellowed paper suggested that the cause of the yellowing was diffusing into the paper making atmospheric pollutants a more likely cause. We suggest that the increased porosity of inkjet papers may have made them more susceptible to oxidizing gases in atmospheric pollution or outgassing from packaging materials as compared to more traditional paper formulations.
2:45 PM - TC3.5.02
Composition, Processing and Properties of Composite Ceramic Sickle Blades from Mesopotamia in the Third Millennium B.C.E.
Patrick Horrocks 1 , Pamela Vandiver 2
1 Materials Science and Engineering University of Arizona Tucson United States, 2 Materials Science and Engineering University of Arizona Tucson United StatesShow Abstract
Ceramic tools were made in lowland Mesopotamia from the fourth to early second millennium BCE. Early on hammars, adzes, axes and sickles were made. By 2350 BCE, only sickles were made, presumably as a popularar technology, fired by farmers in fields surrounding tells. The best blades were resharpened by pressure flaking. The compositions, phase assemblage, firing temperature range, material limits on processing, and properties have been assessused using Xeroradiography, SEM-EDS, XRD, EPMA, strength and hardness tests of replicate test tiles.
3:00 PM - TC3.5.03
Studies on the Developing Process of the Pottery Coatings of Neolithic Period in Yellow River Basin
Xiaoke Lu 1
1 Shanghai Institute of Ceramics Chinese Academy of Sciences Shanghai ChinaShow Abstract
In this study, the EDXRF, EPMA and Raman spectroscopy were used to analysis the chemical composition and microstructure of the pottery coating at several archaeological sites in Yellow River basin. The raw material and the technical craft of the coatings were studied to discuss the development of the pottery coatings and the relationship with origin of glaze. The results show that the bright green pottery coating of Yangshao culture at the Anban site contains much potassium and phosphorus, which may relate to the plant ash. The white pottery coating on the surface of colored pottery at the Xipo site can be divided into two types. The deep red pottery coating was also found on the surface of some red potteries at the Xipo site, which was main colored by hematite. The black pottery coating was found on the surface of some black and grey pottery samples at the Taosi site, Wadian site and Tonglin site. The main chemical composition characteristic of the black pottery coating is high contents of Al2O3 compared to the pottery bodies. The glaze thickness of proto-porcelain at the Erlitou site more than 100µm and continuously on the surface. In summary, the total flux content of RXOY in these pottery coatings wasn’t sustained increasing as the time forward from Yangshao culture to Longshan culture and Erlitou culture. In addition, because of the low firing temperature and the fusible body, the pottery coatings of Neolithic period couldn’t transform to vitric glaze. But we beleive that the long-term accumulation of pottery coating technology should provide important technical supports to the invention of glaze.
3:15 PM - TC3.5.04
Reconstructing the Firing and Pigment Processing Technologies of Corinthian Polychrome Ceramics
Catherine Klesner 1 , Jay Stephens 2 , Pamela Vandiver 1
1 Department of Materials Science and Engineering University of Arizona Tucson United States, 2 Department of Anthropology University of Arizona Tucson United StatesShow Abstract
Polychrome decorative ceramics from Corinth, Greece, produced during the 8th-6th centuries BCE were luxury goods widely traded throughout Greece and the Mediterranean. This pottery was made from local, highly calcareous clay and was adorned with a variety of mineral based pigments, which produced distinctive white, black, red, wine red, and purple colors upon firing. Not only were the ceramics widely traded, but the techniques developed in the Corinthian workshops, notably black-figure, were later adapted by other regions. This research deepens our understanding of the complex pigment processing and firing technologies employed in the production of Corinthian ceramics. Through the study of Corinthian ceramics from the Dr. Marie Farnsworth collection housed at the University of Arizona, the production and analysis of replica ceramics and pigments, and the characterization of 13 clay samples collected in and around the American School of Classical Studies in Athens (ASCSA) excavation of Ancient Corinth, we have a more complete picture of the complex pigment manufacturing and firing technology. Analytical techniques including Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy energy-dispersive spectroscopy (SEM-EDS), x-ray diffraction (XRD), wavelength-dispersive electron microprobe (EPMA) and focused ion beam scanning-electron microscopy (FIB-SEM) were employed in the analysis.
TC3.6: Use of Portable Instrumentation for In Situ Scientific Investigation of Cultural Heritage
Wednesday PM, November 30, 2016
Hynes, Level 3, Room 303
4:30 PM - TC3.6.01
Micromorphology at the Minoan Site of Koumasa, Crete—A Test Case for Innovative Fieldwork in Unorthodox Conditions
Doron Boness 1 , Yuval Goren 1
1 Ben-Gurion University of the Negev Beer-Sheva IsraelShow Abstract
Micromorphology is a research method originally applied in soil sciences. This method has also been increasingly applied in archaeological research ever since the 1980’s. The method is based on the examination of large-sized thin sections under a polarizing-light microscope, prepared from undisturbed blocks of sediments and archaeological materials. Principles of optical mineralogy are then employed in order to identify archaeological and environmental features on the micro scale. Applications of this method examine issues such as: study of construction materials – provenance of raw material and technology; micro-stratigraphy and site formation processes; and identification of various human activities.
However, this method is highly involved and time-consuming; standard procedures require working in laboratory conditions. This requirement hampers the use of this method in endangered archaeological sites in rural locations where expensive and well-equipped laboratories are inaccessible. The established procedures begin with the delicate removal of undisturbed intact blocks of in situ sediments and other archaeological materials, followed by drying the samples in the oven in the laboratory for a week, their impregnation with highly viscous epoxy, cutting them with a diamond saw, polishing them thoroughly, and ending with the preparation of 5x7.5 cm thin sections. These cumbersome procedures – developed and standardized in the 1980’s - have hindered the production of “real time” information by micromorphologists working at remote archaeological sites. Such information could potentially be crucial to both the excavator and the micromorphologist in forming the appropriate research questions and field strategies. In addition, legal limitations on exporting archaeological materials from certain countries often result in complicated and time-consuming bureaucratic procedures in attaining the appropriate permissions. Thus, both the archaeological and legal realities necessitate the development of new technical field procedures in micromorphology, involving locally available materials and transportable equipment. Moreover, the introduction of such techniques may assist local researchers in establishing low-cost but still effective laboratories where funds are limited. Because micromorphological results are quite interpretative and contextual, modern research also combines micromorphology with other complementary destructive and non-destructive methods, which together may be termed 'microarchaeology'.
Here we present some new technical aspects of micromorphological field work developed at the Minoan site of Koumasa, Crete, aimed at improving fieldwork procedures, and applying micromorphological and other non-destructive methods. This facilitated, for the first time, a micromorphological study of in situ features in a multi-featured rural Minoan site, including monumental tholos tombs, a village and an assumed public building.
4:45 PM - TC3.6.02
Assessing the Effect of Corrosion and Conservation on pXRF for the Analysis of Corroded Copper and Silver Alloys
Stavroula Golfomitsou 1 , Myrto Georgakopoulou 1
1 UCL Qatar Doha QatarShow Abstract
This study discusses the influence of corrosion and conservation treatments on the accuracy of non-destructive surface elemental analysis using portable X-ray Fluorescence spectroscopy (pXRF). Restrictions in relation to sampling and the production of affordable and easy to use portable setups make the use of non-invasive methods of analysis a popular solution in museums. A number of questions can be raised regarding the accuracy of the results obtained as regardless of advances in analytical performance, results can be skewed depending on surface alterations the object has been subjected to. Metals are susceptible to corrosion and objects are often covered with corrosion products. Different corrosion forms can lead to depletion of metals within the alloy with subsequent enrichment in another metal (e.g. dezincification). Removal of corrosion layers as part of cleaning process also results in surface compositional changes. To assess the degree these affect the analytical outcome, a number of measurements were undertaken on alloys of known composition with the aim to explore systematically the way different deterioration mechanisms and cleaning affect the results of surface composition. Bronze (7.5-8.5% Sn), brass (30% Zn) and a silver alloy (Cu 7.5%) were used analysed using pXRF to examine deviations from the composition of the original alloys. Prior to the analysis, the performance characteristics of the instrument were assessed using relevant Certified Reference Materials. The samples were corroded and cleaned at different levels and the analysis was carried our using an Olympus Innov-X Premium handheld system. Repeated analyses were taken in order to assess material homogeneity taking into account instrument precision. The results are discussed comparatively with those of the original alloys. Factors under investigation include the extent and type of corrosion, surface texture, morphology and geometry of analysed area and cleaning method (mechanical and chemical). Preliminary results highlight the variations in chemical compositions caused by different types of corrosion and surface cleaning. The work continues with complex multilayers of corrosion products of different composition and densities to imitate real-life conditions. This will allow a more accurate assessment of the methodologies used and the factors resulting in possible data distortion and deviation from the real values. Understanding the extent of deviation can help in the interpretation of data collected from corroded surfaces. The paper aims to propose methodologies for best practice for the analysis of metal artefacts using pXRF.
5:00 PM - TC3.6.03
A Decade of Portable (Hand-Held) X-Ray Fluorescence Spectrometer Analysis of Obsidian in the Mediterranean—Many Advantages and Few Limitations
Robert Tykot 1
1 University of South Florida Tampa United StatesShow Abstract
Starting in 2007, a portable, hand-held X-ray fluorescence spectrometer was used to elementally analyze and determine the geological source of obsidian artifacts in the Mediterranean, effectively replacing the instruments used in my previous research studies - INAA, LA-ICP-MS, ED-XRF and an electron microprobe with WDS. Approximately 400 geological obsidian samples from the Mediterranean island sources, and 7500 obsidian artifacts from prehistoric sites in Italy, France, Croatia, Malta, Tunisia, Greece, Cyprus, Turkey, Israel, and Egypt have now been analyzed by pXRF. Overall, the pXRF can distinguish all of the individual sources, based on the composition of Fe and trace elements Rb, Sr, Y, Zr, and Nb, as well as assign artifacts specifically to most subsources and thus addressing archaeological research hypotheses about trade and exchange in many different time periods.
For the Italian islands of Lipari, Palmarola, Pantelleria, and Sardinia, and the Greek islands of Melos and Giali, it is demonstrated that it is scientifically and archaeologically important to address the usage of obsidian from specific volcanic flows/subsources regarding the physical properties of the raw material (size of natural blocks, color, translucency, phenocrysts) and their production practices (direct/indirect percussion, artifact type and size), whether there was selection of specific obsidian material in comparison to other lithics (e.g. chert) for certain tool types, and how this changed over time from their initial use as early as the Upper Paleolithic until the Bronze Age. The presence of cores, debitage, blades and other tools at archaeological sites indicates local production, while the absence of primary reduction waste flakes suggests the main preparation of cores closer to the geological source, most likely by lithic specialists.
The analysis of such a large number of artifacts, including 50 or more from 60 different archaeological sites, allows for statistical comparison between individual sites and their contexts (e.g. residential, burial/ritual, other), geographic areas (e.g. coastal/inland, highland/lowland) and distance from geological sources, and changes over time (socioeconomic, technological). The frequency of transport between island sources and mainland sites is suggestive of maritime capabilities also for the transport of domesticated animals, ceramics, and other materials.
But are there any potential archaeological problems in using a portable XRF and its more limited detection capabilities of trace elements? For the Mediterranean in particular, the pXRF will not distinguish all of the subsources for Palmarola and Pantelleria, but does that impact archaeological research on obsidian usage from these islands? This will be discussed along with the highly beneficial “package” of analyzing great numbers of artifacts non-destructively and rapidly without needing to export them from museums and facilities in many countries.
5:15 PM - TC3.6.04
Portable in Practice—Diagnostic Investigations Using Portable Instrumentation for Materials Analysis of Architectural Surfaces in the Tablinum of the House of the Bicentenary
Kiernan Graves 1 , Leslie Rainer 1 , Giacomo Chiari 1 , Ilaria Capatano 4 , David Carson 1 , Gianluca Gennarelli 4 , Arlen Heginbotham 1 , Nicola Masini 3 , Francesca Pique 2 , Maria Sileo 3
1 Getty Conservation Institute Los Angeles United States, 4 Institute for Electromagnetic Sensing of the Environment National Research Council of Italy Naples Italy, 3 Istituto per I Beni Archeologici e Monumentali National Research Council of Italy Potenza Italy, 2 University of Applied Sciences and Arts of Southern Switzerland (SUPSI) Lugano SwitzerlandShow Abstract
Portable in practice: diagnostic investigations using portable instrumention for materials analysis and mapping of decorated architectural surfaces in the tablinum of the House of the Bicentenary at Herculaneum.
The conservation of the architectural surfaces in the tablinum of the House of the Bicentenary at the ancient Roman site of Herculaneum is a collaborative project of the Getty Conservation Institute, the Herculaneum Conservation Project and the Soprintendenza Pompeii. The tablinum was selected as a case study given the significance, beauty, and severe deterioration of its decorated surfaces. A multi-disciplinary team with a wide range of expertise, comprised of conservators, chemists, geo-physicists, engineers, and conservation scientists, worked in partnership across a number of institutions with the objective to study the wall paintings in the tablinum. Scientists and conservators worked together to test the feasibility of portable techniques and in situ investigations to better understand Roman painting technology; identify previous restoration materials; determine the presence of alteration products; and characterize deterioration mechanisms commonly found on architectural surfaces at archaeological sites of the Vesuvian Region. The conservation program follows a methodological approach beginning with background research and scientific study to inform the conservation treatment.
The use of portable, in situ, and generally non-invasive instrumentation such as X-ray fluorescence spectroscopy, laser speckle interferometry, Fourier-transform infrared spectroscopy, X-ray diffraction spectroscopy, ground penetrating radar, infrared thermography, digital microscopy, and a variety of imaging techniques was integral to the process. These analytical methods provided a scientific understanding of the Roman wall paintings, their physical history and causes of deterioration. Techniques employed during this phase focused on mapping large surfaces of wall paintings as opposed to point-based analysis and sampling. The collection and interpretation of the instrumental data has been critical to the design and implementation of appropriate passive and remedial interventions to stabilize the architectural surfaces and mitigate deterioration. The paper will present the results of the investigations using portable instrumentation along with a discussion of the capabilities and limitations of each technique and the practical implications of their use for architectural surfaces on archaeological sites.
5:30 PM - TC3.6.05
Non-Destructive Investigation on the Alloy Components of Chime-Bells from the Tomb of Marquis Yi of the Zeng State by Portable XRF Alloy Analyzer
Xudong Jiang 1 , Youlian Liu 2 , Chun Lv 1 , Songluan Zhou 1 , Chunxu Pan 2
1 Hubei Provincial Museum Wuhan China, 2 Wuhan Machinery Technology Research Institute Co.,Ltd. Wuhan ChinaShow Abstract
Chime-bells from the Tomb of Marquis Yi of the Zeng State, one of Chinese cultural relics forbidden to be exhibited abroad, unearthed in 1978 in the Zeng-hou-yi Tomb in Sui County, Hubei Province, China. Set on a curving shaped copper and wood frame, the whole 65 pieces of chime bells is arranged in eight groups and three layers.
The chemical components of the set of chime-bells were studied once by SEM-EDS before, in which the alloy compositions of only 5 pieces of bells were measured for the destructive characterization. In our latest research, the portable XRF alloy analyzer was applied to investigate different groups of 65 chime-bells in order to discover whether the alloy compositions changed in different groups. The chemical compositions of 19 bells among 65 were obtained for the first time, which showed that the Sn contents ranged from 9.6 to 13.7 wt.% in high-pitched bells (No.: T1.1-T1.6) and from 16.2 to 19.1 wt.% in low-pitched bells (No.: B1.1-1.3 and B2.1-2.10). It reveals high-pitched bells with low Sn content, while high Sn content in low-pitched bells. This initial results just coincide with national occupation standard in China (JB/T 10974-2010: Art casting musical instrument), 12-14 wt.% in high-pitched bells and 14-16 wt.% in low-pitched bells.
It reveals that our ancients in early Warring States period (433 B.C) had mastered the tuning technique of chime-bells by changing Sn contents in bronze. This significant discovery is expected to rewritten the history of casting of musical instrument in China.
5:45 PM - TC3.6.06
The Organisation of Artistic Production in the Medieval Glass-Painting Workshop of John Thornton—An Archaeometric Investigation Using Handheld pXRF
Laura Adlington 1 , Ian Freestone 1 , Nick Teed 2
1 UCL Institute of Archaeology London United Kingdom, 2 York Glaziers Trust York United KingdomShow Abstract
A stained glass window represents a complex chaîne opératoire, from glass-making and acquisition, through design and planning, to cutting and painting the glass and construction of the window. Medieval windows therefore have the potential to deepen our understanding of medieval craft workshops, in particular through a materials science approach.
The Great East Window of York Minster, created by John Thornton of Coventry and his workshop in 1405-1408, is the largest expanse of medieval glass in Britain and is regarded as a masterpiece. A comprehensive study of twelve panels across the main lights using a combination of analytical techniques has allowed the investigation of the organisation of artistic production within Thornton's workshop. Handheld portable x-ray fluorescence spectrometry (pXRF) was used to quickly analyse the surface of over 900 pieces of glass, while samples were removed from a subset of 250 glass pieces for analysis of the cross-section by electron microprobe (EPMA-WDS). Surface analysis of medieval glass can be highly problematic due to the deterioration of the glass and the resultant layer of altered composition, which especially affects the analysis of light elements, including calcium and potassium. However, heavy trace elements strontium and rubidium are less affected by surface conditions and are well measured by pXRF. Furthermore, strontium and rubidium were found to serve as proxies for calcium and potassium, respectively, allowing the identification of compositional groups, reflecting different recipes and raw materials.
Furthermore, these trace elements allow the identification of different batches, or sheets, of glass. Spatial analysis of these batches of glass across a panel, a row and the window has allowed the identification of the work of different craftsmen, both masters and apprentices, and the examination of the organisation of artistic production, including changes in production from the beginning to the end of the enormous three year project. Other topics related to the life history of the window will be discussed, including the acquisition of the glass and centuries of conservation.
Aaron Shugar, SUNY - Buffalo State
Stavroula Golfomitsou, UCL Qatar
Chandra Reedy, Univ of Delaware
Pamela Vandiver, Univ of Arizona
Society for Archaeological Sciences, XGLab and nSynergies
TC3.7: Characterization and Interpretation of Variability—Stylistic Types and Technological Typologies
Thursday AM, December 01, 2016
Hynes, Level 3, Room 303
9:00 AM - *TC3.7.01
Research on the Science and Technology of White Porcelains from Ding Kiln
Weidong Li 1 , Hongjie Luo 2 , Xiaoke Lu 1 , Qiang Li 1
1 Shanghai Institute of Ceramics, Chinese Academy of Sciences Shanghai China, 2 Shanghai University Shanghai ChinaShow Abstract
Under the influence of Xing kiln, Ding kiln began producing white porcelain in the middle and late Tang Dynasty ((618-907 AD), and gradually emerged as the best producer of white porcelain during the Song dynasty. Ding kiln declined during the Yuan Dynasty (1279-1368 AD).
Using a series of scientific methods, this research studies the chemical composition, microstructure, firing temperature, physical properties, appearance features and other aspects of the white porcelain samples from the 2009 archaeological excavation. The 188 samples selected in this study cover the entire time series of Ding Kiln from late Tang Dynasty to the Yuan Dynasty. By taking multiple perspectives, this study attempts to reveal fully the physical and chemical characteristics of white porcelain of Ding kiln as well as its development and evolution.
The scale, variety and circulation of Ding kiln products are considerable. White porcelain wares from Ding kiln long served as tributes for the Song imperial court, and as important commercial goods during the Southern Song (1127-1279 AD) and Jin (1115-1234 AD) Dynasties. Ding kiln has a profound impact on the subsequent porcelain making industry in ancient China. It embodies a series of important breakthroughs in porcelain making techniques. Kaolin, feldspar, quartz, dolomite, talc, occurring near the kiln sites can be used as the raw materials for the manufacture of the body as well as the glaze. This provides the material basis for the manufacture of high quality and refined white porcelain. Improvements were also made in kiln structure accompanied by the increase of firing temperature. The dome-shaped kilns have half-reverse flame, large and deep fire chamber, small kiln room, developed ventilation and large chimney. Along with the abundant wood or coal resources nearby, these kilns ensure the high temperatures for porcelain firing. Ding kiln in Northern Song Dynasty (960-1127 AD) invented the inversion firing method and the sagger assembled by stacked ring-supporters, to maximize the use of space and prevent ware distortion. These inventions improved the output and quality of porcelain. As a major technological innovation, this achievement played an important role in promoting the development of ancient China's porcelain industry. The world famous porcelain making site--Jingdezhen was profoundly influenced by it. White porcelain of Ding kiln is also noted for the decorative techniques including engraving, scratching and stamping. The unique decorative patterns are exquisite and elegant. The recipes used at different stages have also been deduced based on the raw materials discovered from archaeological excavation, providing references for the history of Ding kiln techniques. Additionally, white porcelains made in Ding, Xing, and Gongyi kilns were compared with each other.
9:30 AM - TC3.7.02
Talc-Rich Black Tibetan Pottery of Derge County, Sichuan Province, China
Chandra Reedy 1 , Pamela Vandiver 2 , He Ting 3 , Ying Xu 1
1 University of Delaware Newark United States, 2 University of Arizona Tucson United States, 3 Sichuan Provincial Institute of Cultural Relics and Archeology Chengdu ChinaShow Abstract
Tibetan potters in the Puma Village of Maisu Valley (Derge County, Garze Tibetan Autonomous Prefecture, Sichuan Province) have a long tradition of making black pottery. While black pottery is common in many Tibetan areas, and throughout China, both the materials and the firing techniques of Puma potters are unique. The unusual raw materials permit non-kiln firing that results in high-quality ceramics well suited for heating and cooking; they are traditional analogues of modern industrial ceramics. A local clay source is used, a white calcareous clay with black veins of graphite. The clay is ground by hand and sieved to ensure a very fine particle size. The clay is mixed with a material the potters call “gold stone”, obtained from surface deposits; analytical studies confirm that its primary constituent is talc. The stone also contains hematite, often partially hydrated to limonite which forms yellow stains over much of the surface. The rock is best described as a ferruginous talc schist (or ferruginous steatite/soapstone because it is more massive than schistose in structure). The stone is ground to a fine powder and mixed with clay, usually with a 50-50 ratio. Fabrication of objects is done completely by hand, incorporating the use of molds. The surface is carefully smoothed to produce a very shiny surface, as the talc particles become strongly oriented during this finishing step. A wide variety of objects are made, including cooking pots, liquid containers, tea pots and cups, hot pots and braziers, vases, incense burners, and others. Firing is done as a two-stage process. For the first firing, objects are placed on a metal grate raised above ground, with wood (local pine) placed in a metal slot just beneath the grate. The heat is gradually increased over two hours to slowly release any remaining water, to avoid cracking. The fired objects are then slowly cooled for one full day. After this oxidized firing, the graphite-rich pots are gray in color. The second, higher-temperature firing takes place in a pit dug into the ground adjacent to the metal grate, with wood and sawdust piled around the objects to create the reduced atmosphere that makes the shiny pots very black. What is most significant about this technology is the innovative raw material mix. The large amount of talc, combined with a calcareous clay, promotes vitrification at low temperatures. The talc also improves many properties that increase the usefulness and lifespan of the pottery. These properties make talc an important addition to modern industrial ceramics, but it is very rare in traditional hand-made pottery, especially at the high levels used in the Derge ceramics.
9:45 AM - TC3.7.03
Islamic 12th Century CE Glazes from Aktobe, Kazakhstan, and Comparison to Modern Practice in Afghanistan and Uzbekistan
Pamela Vandiver 1 , Sean Arnold 1
1 University of Arizona Tucson United StatesShow Abstract
Ceramics excavated from 12th century strata at Aktobe, southern Kazakhstan, were analyzed for fiiring temperature range, composition and microstructure, and compared to technological practices used in modern glazes and bodies by potters in contemporary Afghanistan and Uzbekistan. Analytical techniques included optical microscopy, radiography, scanning electron microscopy with energy dispersive x-ray analysis, microprobe analysis (EPMA), differential thermal analysis, and analysis of refiring experiments. Special visual effects are described, and faults in and limitations of materials and processing are interpreted.
10:00 AM - TC3.7.04
Characterization and Comparative Analysis of Ancient Earthen Plasters from the American Southwest
Angelyn Bass 1 , Douglas Porter 2 , Mike Spilde 3
1 Anthropology University of New Mexico Albuquerque United States, 2 Engineering University of Vermont Burlington United States, 3 Institute of Meteoritics University of New Mexico Albuquerque United StatesShow Abstract
Pueblo people of the southwestern United States have traditionally used earthen materials for building and architectural embellishment. Structures over a thousand years old, built and decorated with earth, are likely to have been constructed with some of the same materials and practices in use today. This paper focuses on the characterization of ancient earthen plasters/renders at three Puebloan sites associated with the Sinagua, Cedar Mesa, and Hohokam peoples. The sites include a defensive multi-room alcove structure at Montezuma Castle (AZ); a kiva used for textile production at Bare Ladder Ruin in Natural Bridges National Monument (UT); and a multi-story puddled earth structure possibly intended for ceremonial use at Casa Grande National Monument (AZ). Primary periods of occupation were between the 11th and 14th centuries.
Earthen plasters and mortars were used extensively in the construction of ancient southwestern architecture, including for leveling and finishing walls; for pointing stone and earthen unit masonry; to fabricate built-in architectural features such as mealing bins, loom anchors and nichos; as multi-coat floor surfaces; as a final finish for kiva roofs; as colored washes on interior walls; and as a ground for incised embellishments. Though these plasters differ in terms of material components and the contexts in which they were used, they share characteristics that provide clues as to how materials were selected, processed, and used.
Analysis of plasters and mortars typically requires combining petrographic analysis with characterization of aggregates following acid digestion of binder constituents in a bulk sample (ASTM C 1324-05). Aggregate characterization includes determination of proportion, particle morphology, size distribution, mineralogy, and chemical reactivity. However, obtaining bulk samples of culturally significant material is often impossible. Combining microscopy with computer assisted image-analysis techniques allows for a fairly detailed characterization of ancient plasters and mortars based on relatively small samples. In these circumstances, image analysis of photomicrographs can yield important information on volumetric proportions of aggregates, matrix, and void space, grain size and pore distribution, and particle morphology.
For these ancient Native American sites, sample sizes were small to limit impacts on integrity. Analysis made maximum use of optical microscopy, x-ray diffraction, SEM/EDS, and image analysis, and included investigation of multi-coat plaster systems; application methods; identification of clay minerals and soluble salts; physical characteristics affecting performance; deterioration mechanisms; and surface embellishment. In addition to summarizing the results of plaster characterization at each site, this paper will discuss the analytical techniques used to examine small samples, the range of results that can be obtained, and evaluate the benefits/limitations associated with each.
10:15 AM - TC3.7.05
Functional Demarcation of Traditional Off-White Colored Water Pots Manufactured from Rajasthan Clayey Soils and Red Colored Water Pots from Gujarat Clayey Soils Using Spectrographic, Cooling and Strength Studies—A Case Study from Jodhpur, Rajasthan, India
Amrita Kaurwar 1 , Raj Satankar 1 , Sandeep Gupta 1 , K. Usha 2 , Kuldeep Kothari 3 , Alfred Soboyejo 4 , Valentine Roux 5 , Anand Plappally 1
1 Indian Institute of Technology Jodhpur India, 2 Mahatma Gandhi University Kottayam India, 3 Rupayan Institute Jodhpur India, 4 Ohio State University Columbus United States, 5 Directrice de Recherche Centre National de la Recherche Scientifique Nanterre FranceShow Abstract
Off-white water pots have sustained traditional acceptance through ages in Jodhpur compared to red colored water pots imported from the neighboring Gujarat state. Both the pots hold 20 liters of potable water. The fluorescence spectroscopy reveals dominance of silica, alumina and iron oxide in red pots from Gujarat and whereas off-white of Rajasthan are also appended with a hint of excess CaO and MgO. Fourier transform infrared spectroscopy study reveals a firing temperature of 800oC for off-white pots comparatively less than those for red pots. Less percent of Fe2O3 and excess of MgO in off-white compared to red water pot are responsible for the color differentiation. Off-white pots showcased better degree of cooling compared to red pots. Better resistance to load was observed in off-white pots compared to red pots. This study may imply influence of hidden techno-functional aspects towards sustainability of off-white pots in Jodhpur, Rajasthan.
11:00 AM - TC3.7.06
Analysis and Replication Studies of Prehistoric Chinese Ceramics from the Qijia Culture
Elizabeth La Duc 1 , Katherine Eremin 1 , Angela Chang 1
1 Harvard Art Museums Cambridge United StatesShow Abstract
Twelve ancient Chinese ceramics from the early Bronze Age Qijia culture (c. 2200 – 1500 B.C.E.), in the collection of the Harvard Art Museums, were the subject of an interdisciplinary research project to explore questions about manufacturing techniques, specifically details of formation and decoration. While the Qijia culture, centered in the Gansu and Qinghai provinces of northwest China, is historically important as one of the earliest metalworking cultures of China and as a center of intercultural communication between China and central Asia, detailed scholarship about the culture is still emerging. Qijia ceramics have been categorized by typology, but little has been done regarding methods of manufacture. This study used digital x-radiography to investigate ceramic production, especially the coil-building process and the use of a turntable versus a fast wheel. While film radiography has often been used to examine ceramics, digital radiography presented new capabilities as well as challenges, which will be described. Replication of Qijia ceramics through the making of test vessels and tiles at the Harvard Ceramics Program provided additional insights into their manufacture and their surface decoration techniques, often described as cord-impressed. For example, test tiles showed what tools might have been used to produce different surface patterns. In addition, the ceramic paste and its natural inclusions and temper were analyzed. Finally, x-ray fluorescence spectroscopy and polarized light microscopy were used to detect cinnabar in the first definitive identification of the valuable pigment’s usage in the Qijia culture. The presence of cinnabar is significant because it illustrates interregional trade as well as increasing social complexity.
11:15 AM - TC3.7.07
Research into Coal-Clay Composite Ceramics of Sichuan Province, China
Chandra Reedy 1 , Pamela Vandiver 2 , He Ting 3
1 University of Delaware Newark United States, 2 University of Arizona Tucson United States, 3 Sichuan Provincial Institute of Cultural Relics and Archeology Chengdu ChinaShow Abstract
In 2014, an American-Chinese collaborative survey of traditional pottery workshops of Sichuan Province encountered a ceramic material not previously known from any geographic context, a coal-clay composite (half powdered coal cinder and half clay). In addition, its firing is performed in a unique manner not documented at any other location, in China or elsewhere. Potters use a round in-ground coal-fired kiln with a shallow pit and a removable hemispherical metal-reinforced ceramic dome cover. This cover is lifted up and the pots are removed when orange hot, to be placed into a glaze pit adjacent to the kiln. Organic material is added, and the glaze pit is closed by a metal cover. Reminiscent of American interpretations of Japanese raku-style kilns, the organic material burns rapidly and forms a thin and porous natural ash "glaze" on the exposed surfaces of the pots. The finished product is a very hard, black, ceramic material with a shiny, silvery, and sometimes bubbly surface. This innovative double-firing process in subterranean pits with the first firing being the higher temperature one and the second being a high-temperature surface reduction, the use of coal cinder as about half of the ceramic body, and the mechanism of producing a porous glassy surface are all developments that result in ceramics resistant to thermal shock and brittle fracture, making them ideal for their most typical use as braziers, soup and stew pots, and hot pots. There are two locations in Sichuan Province where these ceramics are made, Yingjing (in Central Sichuan) and Gaoxian (in Eastern Sichuan). In Yingjing, multiple workshops making similar products are located on one street. In Gaoxian there is one very small family-run workshop. The potters in both locations claim a long (2,000-year) history to their materials and procedures, and we are currently investigating the chronology and possible sources of this tradition. Here we will report on initial studies of the raw materials, fabrication methods, drying and firing regimes, kiln designs, workshop organization, product types and markets, and the microstructure, mineralogy, porosity, and physical, mechanical, and thermal properties of finished products. Our goal is to understand how and why such unique materials and production methods might have emerged in Sichuan Province, how the unusual raw materials and firing methods impact the material properties of these ceramics, and the fuller context of how these products may fit in with other cultural developments of the region (such as innovative cuisine and dining practices).
11:30 AM - TC3.7.08
Reverse Engineering the Physical Chemistry of Making Egyptian Faience through Compositional Analysis of the Cementation Process
Pamela Vandiver 1 , Kayli McArthur 1
1 University of Arizona Tucson United StatesShow Abstract
Sheets of glass from the Byzantine Shops at Sardis, Turkey, dated to the eighth century C.E., were studied to determine their method of manufacture, compositional variation and working properties using the techniques of SEM-EDS, EPMA and DTA. The characteristics of the glass do not fit criteria for known methods of making sheet glass. Replicative studies were conducted in the Glass Processing Lab of the University of Arizona Materials Science Department, and compared to the excavated artifacts.
TC3.8: Characterization and Development of New Materials for Use in Conservation Treatments II
Thursday PM, December 01, 2016
Hynes, Level 3, Room 303
11:45 AM - *TC3.8.01
Earth to Earth, Dust to Dust—Material Analysis, Conservation Protocols and Future Research of Ancient Near Eastern Cay Cuneiform Tablets
Yuval Goren 1
1 Ben-Gurion University of the Negev Beer Sheva IsraelShow Abstract
The era dating from the 3rd to the end of the 1st millennia BCE constitutes the heyday of the great empires of the Bronze and Iron Ages, during which the ancient world’s great corpuses were compiled. This time span witnessed the production and dissemination of a large quantity and variety of textual materials written upon clay tablets in several languages using the cuneiform script (i.e. Akkadian, Sumerian, Hittite, Hurrian and Northwest/West Semitic dialects). This immense body of textual materials became widespread from Mesopotamia and elsewhere to be received in places far and wide—from Susa in Iran to Ugarit on the Syrian coast, and in culturally diverse centres, such as Hittite Anatolia or Pharaonic Egypt. These cultural interactions acted, throughout long and complex transmission processes, as agents of intercultural interactions. Hence, the “Cuneiform Culture” as it is often referred to, can be seen as the only source at hand of the wisdom, literacy and intellectual creation of the cradle of civilization.
Today, cuneiform tablets act as a unique source of data stored in museums and other collections. Because the origin of the “Cuneiform Culture” was in West Asia, the removal of great numbers of clay tablets - often unfired or lightly fired and effected by post-depositional processes - from their usually arid or subhumid environments to other climatic conditions presents nowadays countless problems. Unfortunately, the survival of these collections is seriously threatened; deterioration, exfoliation, contamination and physical disintegration are affecting these artifacts. In addition, large collections of cuneiform tablets are threatened by the current political events in their countries of origin. Some of the landmark sites in Syria and Iraq, where major archives are found, are subjected to looting and sabotage by political and religious extremists. The constant decay of these archives represents a loss of a major aspect of our cultural heritage, and poses a threat to future research. This situation calls for the establishment of detailed protocols for the conservation of large numbers of tablets. At the same time, advances in the application of scientific methods in art and archaeology have opened new possibilities for better understanding the provenance, technology, dates, style, and deterioration processes of tablets, with several of the methods becoming less invasive and more precise and accurate. All these require some new thinking, taking in consideration aspects of research and conservation with rigorous and a close cooperation between scientists, conservators and philologists. The application of several aspects of this holistic approach in some case studies is hereby presented.
12:15 PM - TC3.8.02
Role of Case Hardening in the Preservation of the Cavates and Petroglyphs of Bandelier
Douglas Porter 1 , Angelyn Bass 2 , David Broxton 3 , Pat Longmire 4 , Deborah Neher 5 , Thomas Weicht 5
1 School of Engineering University of Vermont Burlington United States, 2 Anthropology University of New Mexico Albuquerque United States, 3 Computational Earth Science Los Alamos National Laboratory Los Alamos United States, 4 New Mexico Environment Department Department of Energy Oversight Bureau Los Alamos United States, 5 Plant and Soil Science University of Vermont Burlington United StatesShow Abstract
Bandelier National Monument (BNM) was created to protect an extraordinary inventory of archaeological resources carved in the 134 m-thick Tshirege Member of the Bandelier Tuff erupted 1.22 Ma ago. From the 12th to the 14th centuries, the Ancestral Pueblo people of New Mexico carved thousands of chambers into soft rhyolite tuffs of the Pajarito Plateau. These rock-cut chambers, called cavates, were used for dwelling, storage, and textile production. This presentation explores the development of rinds, or case hardening, on tuff outcrops at BNM. Understanding the mechanisms of rock deterioration and the interactions of biological and geological systems in the formation of case hardening is essential to management of the resource.
The glass-rich tuffs at the base of the Tshirege Member (where 95% of the archaeological material is found) are poorly consolidated and susceptible to erosion by wind, rain, and mechanical abrasion, with resultant loss of cultural material. However, rock surfaces develop a protective weathering rind through sedimentation of clay and silt coatings, and colonization of the surface by lichens and microbial crust constituents. These excrete organic acids (principally oxalic acid) that catalyze biogeochemical reactions that lead to the preferential dissolution of Si, Al, and Fe components of the volcanic glass. The mobilized cations precipitate as secondary minerals (principally opal and smectite/sepiolite) in rock pores, creating a durable crust. As crusts develop, imbibition rates at the surface decrease, limiting the potential for additional hydrolytic reactions and improving the erosion resistance of the altered surfaces. Microbial populations initially thrive as they derive nutrients from the dissolution reactions of the glass, but biological activity reaches a maximum and starts to decline as precipitation of secondary minerals limits access to new sources of nutrients, so that alteration processes are self-limiting. The crusts resulting from these interactions are more durable than unaltered tuff surfaces by multiple orders of magnitude.
The interaction of lichens and other microflora with rock surfaces in archaeological sites, monuments, and historic buildings is usually explored in terms of biodeterioration and the resulting damage. As a consequence, design responses from the heritage community are typically focused on removal of microflora. However, this study shows that, under some circumstances, lichens and microflora provide a level of erosion protection to relatively porous and unconsolidated rock substrata that outweighs the biodeteriorative effects. Identifying the contributions of biological crusts to surface improvements may change the way site managers approach monument conservation at a landscape level; understanding the biological contribution may reduce the inclination toward interventionist strategies by providing data that documents both beneficial and destructive impacts on the substrates through time.
12:30 PM - TC3.8.03
A Strategy for the Conservation of Built Heritage Based on the Analysis of Rare Events
Ylenia Pratico 1 , Fred Girardet 2 , Robert Flatt 1
1 ETH Zurich Zurich Switzerland, 2 RINO Sàrl Blonay SwitzerlandShow Abstract
The degradation of materials exposed to the environment is a slow and irreversible process that can involve various mechanisms.
In the case of objects of cultural interest, characterizing such mechanisms and finding solutions to extend the life of their constitutive materials generally relies on accelerated aging tests. However, these are often criticized for their poor ability to represent field conditions and therefore lead field practitioners to become skeptical towards laboratory studies.
This issue emerges from the difficulty in establishing test parameters that are aggressive enough to produce a fast enough degradation, but not too aggressive so as to change the nature of the degradation mechanism.
An example of such a degradation mechanism and the associated potential life-extension solutions can be found in the study of the degradation of clay-bearing sandstones consolidated with ethyl silicates. It has been shown that such treated stones lose the benefit of consolidation within few cycles of wetting and drying. However, typical testing of these treated stones involves complete submersion, which does not represent the conditions on side.
With this study, we propose a modified approach to overcome this obstacle, based on the idea that the degradation of materials is not a continuous process, but rather the result of the accumulation of a limited number of critical events causing most of the damage. These would correspond to specific combinations of damaging conditions and can be identified with the help of the analysis of rare events. For example, theories such as the “grey swan” and the “dragon-kings” suggest that such events can be identified and, in some cases, despite their rarity, predicted.
From this perspective, accelerated testing becomes a question of reproducing faithfully the most damaging of these events, increasing their frequency, without changing their nature or intensity. As an application of this principle, we have developed an automated machine to submit large sandstone samples typical of the cathedral of Lausanne to one sided wetting and drying cycles. Furthermore, to properly simulate extreme but realistic weathering cycles in the laboratory, the Lausanne cathedral was monitored with sensors measuring both water penetration and temperature profiles.
On the basis of the on-site measurements and observations of past degradations, we therefore identify the crytical cycles by means of the analysis of rare events and reproduce them in the laboratory using our instrument.
The combination of on-site measurements and laboratory testing is finally discussed in light of the analysis of rare events, which constitutes the originality of the approach proposed.
12:45 PM - TC3.8.04
Applicability of Femtosecond Lasers in the Cross-Section Sampling of Paintings
Stephanie Spence 1 3 , Takaaki Harada 2 , Athanasios Margiolakis 2 , Skylar Deckoff-Jones 2 , James Hamm 1 , Aaron Shugar 1 , Keshav Dani 2 , Anya Dani 3
1 Art Conservation Program SUNY Buffalo State College Buffalo United States, 3 Art Conservation Program Okinawa Institute of Science and Technology Graduate University Okinawa Japan, 2 Femtosecond Spectroscopy Unit Okinawa Institute of Science and Technology Graduate University Okinawa JapanShow Abstract
Issues in traditional cross-section sampling of paintings with a scalpel, such as crumbling, delamination and paint compression, can deter conservators from sampling fragile paint layers in which the risk of causing further damage from the scalpel is too great. Research was carried out into the use of ultrafast, femtosecond lasers as a less damaging sampling method on paintings that may be too difficult to sample with a scalpel. A Regenerative Ti:Sapphire amplifier system with a pulse duration of 70 femtoseconds, up to 5mJ/cm2 fluence per pulse and a repetition rate of 1 kHz (1000pulses/sec) was used for the experiments. Tests were performed on alkyd and oil paintings ranging in age from the 19th century to 2006. Cuts were attempted at wavelengths of 400 and 800nm, testing variations in speed and power at each wavelength, using spot sizes of approximately 100μm. The optimal laser settings were determined to be 10mW of power at a speed of 10mm/sec and 800nm wavelength. Preliminary results suggest femtosecond lasers could be a viable alternative for paint cross-sections when traditional sampling methods cause unnecessary damage to fragile paintings.
TC3.9: Poster Session: Materials Issues in Art and Archaeology
Friday AM, December 02, 2016
Hynes, Level 1, Hall B
9:00 PM - TC3.9.01
CO2 Snow Cleaning Applied to Art Cleaning
Robert Sherman 1
1 Applied Surface Technologies New Providence United StatesShow Abstract
CO2 Snow Cleaning will be discussed as applied to art restoration and cleaning. The process can remove particles of all sizes along with hydrocarbon and organic residues. Within the material science communities, many applications have been documented, and in recent years, applications have been developed for art cleaning. We will review the CO2 cleaning process with an emphasis on why the cleaning process succeeds or fails, what it can remove or cannot remove, and provide reasons for these results in terms of surface chemistry. Emphasis will be on demonstrated applications including particle removal from surfaces, including baskets and textiles, organic removal from sculptures, soot removal from flat surfaces, cleaning glass sculptures, polishing residue removal, and other applications. Potential applications will be discussed too for photographs, paper, and within archaeology.
9:00 PM - TC3.9.02
Moisture Transport and Sorption in Oil-Painted Linen Canvas Documented by Neutron Imaging
Dominique Derome 1 , Roel Hendrickx 2 3 , Guylaine Desmarais 4 , David Mannes 5 , Anders Kaestner 5 , Ester Ferreira 6
1 Swiss Federal Laboratories for Materials Science and Technology Duebendorf Switzerland, 2 Stiftung Schweizerisches Institut für Kunstwissenschaft Zurich Switzerland, 3 University of Antwerp Antwerpen Belgium, 4 ETH Zurich Zurich Switzerland, 5 Paul Scherrer Institute Villigen Switzerland, 6 Cologne Institute for Conservation Sciences TH Köln Köln GermanyShow Abstract
Moisture is generally recognized as a major damage factor for paintings on textile support. Yet, paintings are often exposed to daily or seasonal variations in relative humidity, although most museums try to minimize such loads.
The paintings of interest here are made of a canvas (often linen textile), a size layer (often animal glue), a chalk-glue ground layer and an oil paint layer (cured oil with different pigments). The canvas and the size used are hygroscopic, but they have different micro- and macro-structures and their hygro-mechanical response to fluctuations of humidity in the surrounding air is different. For instance, the textile is made of flax fibers, which cell walls are a polymer-based (i.e. cellulose, hemicellulose and pectins) nanoporous material, while the glue is a protein-based material characterized by a gel transition temperature (Tg), which decreases strongly with increasing water content, stemming from dissolution at very high humidity and resulting in a subsequent loss of stiffness. Both materials undergo significant swelling and shrinkage under moisture content variation. On the other hand, the oil layer is hydrophobic and comparably stable under varying moisture conditions. The behavior of painted canvas samples undergoing changes in moisture content is documented using neutron imaging experiments in order to better understand the coupled hygro-thermo-mechanical response of paintings as complex layered systems.
Neutron radiography was used to observe in-situ the adsorption and desorption behavior, and the accompanied swelling, of the layered painting system in a time and space-resolved manner. Neutron radiography is based on intensity measurements of a neutron beam transmitted through an object. The high interaction of neutrons with hydrogen allows the quantification of the water present in the samples. Custom sample holders were designed to observe small samples in the ICON cold neutron beamline at SINQ, PSI, Switzerland, exposed to varying relative humidity. With normalization and calibration, we can quantify precisely the moisture content distribution and swelling of the samples. A difference in behavior between canvases impregnated with glue and those covered by a layer of glue is remarked. Swelling and moisture content distribution are documented concurrently, allowing a deep understand of the hygromechanical behavior of the layered systems.
9:00 PM - TC3.9.03
New Approaches to Assess Weathering of Sandstones
Jessica Dassow 1 , Martin Lee 1 , Patrick Harkness 1 , Stefan Hild 1 , Alick Leslie 2
1 College of Science and Engineering University of Glasgow Glasgow United Kingdom, 2 Historic Environment Scotland Edinburgh United KingdomShow Abstract
New approaches for quantifying the magnitude and timescale of weathering processes in sandstones are required in order to develop a better understanding of decay for the preservation of our built heritage. A consistent classification of decay through new methods of measurement will provide empirical data to assess the state of decay. Our project aims to detect the exact length scale (nanometre to centimetre) and timescale (seconds to years) of weathering processes using two new non-/minimally invasive tools. The project focusses on assessing sandstone masonry with an ultrasonic drilling tool to estimate the structural properties and a laser interferometer to measure dilatation over time to nanometre precision.
The ultrasonic drilling tool uses a piezoelectric transducer to convert electrical energy into an ultrasonic vibration of 5 µm. The vibration is amplified by an acoustic horn and transmitted to a drill bit. The consumption of power and the force needed to drill a hole of some millimetres in size is monitored and allows the sample’s structural properties to be deduced. These properties include porosity changes or identification of salt being present in the rock. The use of ultrasonic drilling as opposed to conventional drilling enables faster penetration into the rock with less force on the sample and a decreased wear effect on the drill bits.
With the laser interferometer we aim to observe precisely weathering processes like swelling of clay minerals and salt crystallisation, because of the high spatial and temporal resolutions of the device. The laser interferometer allows measurement of very small (nanometre) scale expansion of a sample and can identify the effects of hourly or daily changes in stone condition.
Once demonstrated in the laboratory, our aim is to predict the decay processes of building materials and use the devices in situ on historical buildings under site conditions.
9:00 PM - TC3.9.04
Experimentation in Manufacturing Zinc Orange Pigment
Kathryn Harada 1 , Aaron Shugar 1 , Rebecca Ploeger 1
1 Buffalo State Art Conservation Department Buffalo United StatesShow Abstract
Zinc orange is a rare and generally undocumented pigment. The brief mention of this pigment in the literature indicated its limited availability to artists in the 19th century. The limited documentation of this pigment clearly states that it is unstable, but does not address any specific issues related to its degradation. The synthesis of the original pigment will be discussed. In addition, a full characterization of the pigment will be presented including XRF, XRD and optical microscopy. Research into its degradation mechanisms were also undertaken and the light fastness of the pigment will also be presented.
Key words: Zinc orange, orangé de zinc, historic pigments, x-ray fluorescence, optical microscopy
9:00 PM - TC3.9.05
The Study of Writing Inks Aging Using Raman Spectroscopy
Vladimir Kochemirovsky 1 , Kseniya Gorshkova 1 , Ilya Tumkin 1
1 Saint Petersburg State University Saint Petersburg Russian FederationShow Abstract
A common way of document falsification is counterfeit the signatures, inscriptions and dates with ballpoint, gel and capillary pens. In some cases, in order to conceal the fraud the paper documents are heated or irradiated by artificial and natural light sources. However, the identification of the date when a writing ink was printed on paper is one of the most difficult tasks in the field of criminology.
When ink is applied on paper a series of processes simultaneously occur: ink drying due to the solvent evaporation, solvent absorption on the surface of the paper and solvent diffusion inside the paper, ink fading due to degradation of colorants and ink solidification due to polymerization of resins.
In this work the durability against light and aging dynamics of heteroatomic aromatic dyes and pigments containing nitrogen atoms used in writing inks was studied using Raman spectroscopy. According to Raman spectroscopy, it was found that depending on the presence of one or another colorant, there are three main types (Type A, Type B and Type C) of blue dye inks used in ballpoint, gel and capillary pens which were studied in this work. Thus, the results obtained in this study can be used for the age estimation of the paper documents up to 15 years.
Raman spectra were obtained using a Senterra Raman spectrometer (Bruker Optics) equipped with three lasers with excitation wavelengths of 488, 532, 785 nm, a laser module confocal microscope (Olympus) and the fiber-optic sensor for spectra recording in an external sample compartment. A fully confocal system is able to operate at three different exciting wavelengths providing the highest possible spatial resolution at the same time. Raman spectra were recorded in the range of 440-1735 cm-1.
The Raman spectra of writing inks showed that colorants (dyes and pigments) have the most pronounced peaks, which were used for the classification of the samples. Thus, all the studied samples can be divided into three types of the Raman spectra recorded at 785 nm based on the presence of a characteristic group of peaks that correspond to one or another colorant.
According to the interpretation of the obtained Raman spectra along with the results of TLC and spectrophotometric experiments, the following types of colorants were proposed:
1. Type A – the alcohol-soluble phthalocyanine blue mixed with thetriarylmethane group of dyes (such as basic violet, crystal violet, methyl violet, fat-soluble purple K, acid bright blue, victoria blue).
2. Type B – the triarylmethane group of dyes.
3. Type C –the phthalocyanine blue pigment.
We would like to thank LLC “Inter-regional economic and legal office” (Saint-Petersburg) for their expertise and contribution to this project. The authors also express their gratitude to the SPbSU Nanotechnology Interdisciplinary Centre, Centre for Optical and Laser Materials Research and Chemistry Educational Centre.
9:00 PM - TC3.9.06
Preliminary Scientific Analysis of the Excavated Bronze Components in the No.1 Funerary Pit of the Tomb of Marquis Yi of Zeng
Yang Li 1 3 , Xudong Jiang 2 , Changping Zhang 1 , Chunxu Pan 3 4
1 School of History Wuhan University Wuhan China, 3 Center for Archaeometry Wuhan China, 2 Hubei Provincial Museum Wuhan China, 4 School of Physics and Technology Wuhan University Wuhan ChinaShow Abstract
Exquisite bronzes were excavated, including chime bells and ritual vessels, in tomb of Marquis Yi of Zeng dated to the early Warring States Period. The amount of excavated bronzes is impressive, and the culture and metallurgical technology they reflected is complex. Once the bronzes discovered, they triggered wide academic interests to study the bronzes of Zeng State. In the No.1 funerary pit (K1), 465 pieces of components of the bronzes were excavated. Previous study divided them into 26 types according to the shape, and argued that they were tent components. This is rare discovery in ancient bronzes, and offers valuable insights into production processes of ancient bronzes.
The chemical compositions and microstructures of the matrix and residuum of the bronze components in K1 were analyzed systemically by physical and chemical laboratory techniques including optical microscopy, scanning electron microscope, energy dispersive spectrometer, portable X-ray fluorescence spectroscopy, and Raman microscopy. The experimental results revealed that: (1) The component was made by Cu-Sn alloy or Cu-Sn-Pb alloy; (2) Different types of components were not made by same alloy or casting bath; (3) two parts of the bell-liked components were made separately, which suggests that the production is probably preliminarily standard according to the combination of the alloy composition; (4) The solders made of tin-lead alloy were observed on the surface of the bronze components (13 types and more than 100 pieces). This technology indicates that the connection between bronze components and wood was not only through mortise and tenon joint structure, but also enhanced by the solders made of tin-lead alloy to strengthen the joint.
9:00 PM - TC3.9.07
Description of an Unusual Decorative Inlay Technique
Susan Stock 1 , Aaron Shugar 2
1 Royal Ontario Museum Toronto Canada, 2 Art Conservation Buffalo State College Buffalo United StatesShow Abstract
This lavishly decorated belt hook in the Far Eastern Collection, Royal Ontario Museum, was reportedly found at, “Jincun - found on site of the old Loyang capital, Honan.'' Based on the hand written label, the belt hook is dated to the Late Eastern Zhou period, 4th-3rd C.B.C.. It is crafted of gilt copper alloy (bronze), covered with inlaid turquoise and a form of filigree (silver wire) forming cloisons along the body. The animal head finial is covered in gold foil with bead eyes.
During microscopic examination and cleaning, an unusual decorative technique was revealed. Like the turquoise inlay, metal inlays tended to be flat pieces of foil or leaf placed into the decorative pattern. However under magnification, small dots resembling repoussé work were seen. But at an area of loss, it became clear that the silver-like metal inlay was actually made from rods packed vertically into the space which formed the inlay. And what appeared to be repoussé was actually the ends of the rods.
Early Chinese ‘wire’ was actually rolled sheet or foil with a void in the centre. Solid wire rods like these are unusual and certainly, rods arranged vertically in this fashion filling cloisons have not previously been described in the literature.
The belt hook will be discussed as will the scientific investigation of the fabrication technology. Analysis will include SEM, XRF and optical microscopy in an attempt to better characterize this unique artifact.
9:00 PM - TC3.9.08
Preserving and Sharing World History via Photogrammetry and 3D Printing—An Interdisciplinary Effort Bridging Archaeology and Materials Science
Lon Porter 1 , Timothy Howe 2 , Zachery Koppelmann 1
1 Wabash College Crawfordsville United States, 2 St. Olaf College Northfield United StatesShow Abstract
Current geopolitical events stress the pressing need for innovative new methods in preserving and sharing the world’s cultural heritage. The increased availability of 3D scanning and fabrication technologies presents an opportunity for fostering powerful collaborations between archeology and materials science. In this work, a new interdisciplinary effort is shared that focuses on digitizing and replicating artifacts originating from Antiochia ad Cragum. Antiochia ad Cragum has a long history, beginning as a pirate haven in the late second century BCE, becoming a Roman city in 41 CE, reaching its height around 200 CE, and finally reaching its end around 800 CE. Throughout, Antiochia remained an important commercial and administrative center. Even after Christianity had spread across Anatolia and many sites began to decline, Antiochia prospered, continuing its role as a social and political center, though now the seat of a Christian bishop. This rich site remained largely unexcavated until the 21st Century when, in 2007, the Antiochia ad Cragum Archaeological Research Project (ACARP), a consortium of researchers from the University of Nebraska, St. Olaf College, Clark University and Usak University gained permission from the Turkish Ministry of Culture and Tourism to begin excavation. Since then, ACARP teams have uncovered or identified a large bath complex with a 1,600 square-foot mosaic floor, the largest in this part of Turkey, a pedimental group whose several statue heads, including a medusa, have been scanned using 3D photogrammetry, a Christian basilica, a colonnaded street, monumental tombs, a temple, one of the earliest Christian communities in Southern Turkey, and numerous other structures yet to be identified. Using both fused deposition modeling (FDM) and stereolithography (SLA) technologies, several artifacts have been successfully replicated at Wabash College’s 3D Printing Fabrication Center (3D-PFC). In addition to recent accomplishments, this presentation will share future directions for the work arising from this collaborative enterprise.
9:00 PM - TC3.9.09
Analysis of Pigments on a 19th-Century Calligrapher's Box
Meltem Sezen 1 , Feray Bakan 1 , Baris Yagci 2 , Filiz Kuvvetli 3 , Ayse Aldemir Kalecik 3
1 Sabanci University Nanotechnology Research and Application Center Istanbul Turkey, 2 Koc University Surface Science and Technology Center Istanbul Turkey, 3 Sabanci University, Sakip Sabanci Museum Istanbul TurkeyShow Abstract
Writing boxes used by calligraphers, for storing and carrying their implements, have often been objects of beauty as well as being functional. A two-level rectangular writing box has a convex lid decorated with landscapes inside and out. However, the picture covering the inside of the lid is in much better condition. This is a landscape stretching to the sea in the distance, seen through a building with a series of arches. The artist has experimented with perspective in depicting the architectural details. A baldachino visible in the background is a notable feature. Sailing ships, portions of land with buildings in the distance that might be islands, and birds flying, are carefully depicted. The pictures on the lid of this writing box illustrate an affinity between traditional calligraphy and European figurative painting, which evolved in the 19th century. They are small-scale examples of the landscapes used in baroque interior mural compositions, which became popular under western influence in the second half of the 18th century.
In this study, a complementary analysis was performed for a deep investigation of the layers of paint in the lid. In order to identify white, red and blue pigments in the samples, Scanning Electron Microscopy (SEM), Energy-dispersive x-ray spectroscopy (EDS), ATR-FT-IR and Raman Spectroscopy techniques were used. SEM-EDS helped for revealing the morphology and elemental distribution in the paint dyes, while FT-IR and Raman spectra enabled tracking the chemical bonds of the dye materials, which correspond to the origins of the samples
9:00 PM - TC3.9.10
Combined XRF and XRD Mapping of Illuminated Manuscript Leaves at the Cornell High Energy Synchrotron Source
Louisa Smieska 1 , Ruth Mullett 2 , Laurent Ferri 3 , Arthur Woll 1
1 Cornell High Energy Synchrotron Source Cornell University Ithaca United States, 2 Medieval Studies Cornell University Ithaca United States, 3 Cornell Library Rare and Manuscript Collections Cornell University Ithaca United StatesShow Abstract
The scope of cultural heritage applications is expanding for macroscopic x-ray fluorescence (MA-XRF), a noninvasive measurement that yields local elemental concentrations. From the distributions and correlations in MA-XRF element concentration maps, some materials can be identified, and faint or buried layers may be revealed. Since XRF is less sensitive to lighter elements, complementary analytical techniques are important in fully characterizing objects. X-ray diffraction (XRD) probes materials with crystalline structure, even those composed of light elements, and has been demonstrated to be capable of resolving buried pigment layers in a painting .
At the Cornell High Energy Synchrotron Source (CHESS), we are evaluating the combination of MA-XRF and scanning XRD for analysis of cultural heritage materials. These measurements can be carried out simultaneously or sequentially, since the optimal conditions for XRF and XRD depend on the particular sample of interest and detector size and efficiency. Our approach combines a 384-element Maia detector to efficiently collect backscattered XRF signal and an area detector to collect powder-like transmission XRD data.
Here, we present the results of a recent MA-XRF and XRD examination of illuminated manuscript leaves from the Cornell Library Rare and Manuscript Collections. Of particular interest to us is the composition of the azurite pigments, some of which contain unusual trace elements. The ability to spatially map both trace elements and local crystalline structures provides unexpected insights that are not evident in point analyses with a portable XRF system.
 De Nolf, W.; Dik, J.; Van der Snickt, G.; Wallert, A.; & Janssens, K. High Energy X-ray Powder Diffraction for the Imaging of (Hidden) Paintings. J. Anal. At. Spectrom., 2011, 26, 910.
9:00 PM - TC3.9.11
Reverse Engineering 8th Century CE Window Glass Processing at Sardis, Turkey
Kayli McArthur 1 , Pamela Vandiver 1
1 University of Arizona Tucson United StatesShow Abstract
From the Byzantine Shops along side the 8th century CE synagogue of Sardis, Turkey were excavated about 50 pounds of transparent flat glass sheets interpreted as very early window glass. We have studied this collection to test the standardization hypothesis using optical microscopy to study size, shape, thickness, edge shape, tool marks, bubble and cord directionalities and their relationships to one another, and weathering phenomena known to be influenced by any grinding and polishing processes. Microstructural and micro-compositional variation were studied using scanning electron microscopy with energy dispersive x-ray analysis (SEM-EDS). Differential thermal analysis (DTA) was used to determine glass transition temperature range. Three traditional methods have been described in the glass technology literature: crown, plate and cylinder methods. The Sardis glass is most similar to criteria expected for cylinder glass, and consistently patterned characteristics evidence a developed technological practice. To test this idea a wooden and several terracotta two-piece molds were made to permit overblowing on one or both ends, and a series of other ideas such as hot glass rings and threads to thermal shock across the glass, and slumping cycles were tested through replicative trials, the results of which are presented. Analysis of glass manufacturing methods in antiquity contribute to the historical knowledge of the mastery of tools and materials along with explaining social and cultural significance. The glass window fragments from Sardis were manufactured using a currently undefined technique, however the fragment’s microstructure matches our proposed method.
9:00 PM - TC3.9.12
Chemical Analysis of Glass Found in Xinfeng Cemetery, Xi’an, Shanxi Province
Yingzhu Wang 1 , Hongjiao Ma 1 , Kunlong Chen 1 , Qinglin Ma 2 , Weigang Sun 3
1 University of Science and Technology, Beijing Beijing China, 2 Chinese Academy of Cultural Heritage Beijing China, 3 Shaanxi Provincial Institute of Archaeology Shaanxi ChinaShow Abstract
The cemetery of Xinfeng is located in Xi’an City, Shanxi Province, dated from the late Warring States period through the Qin dynasty (4th -3rd centuries B.C.E) to the midterm of the Western-Han to Eastern-Han dynasty (2nd century B.C.E to first quarter of 3rd century C.E.). We could explore the history in variable fields by the ancient objects excavated in Xi’an where was a centre represented for the economic, political and cultural at that time.
From more than 700 tombs in Xinfeng cemetery, more than 100 glass wares were unearthed from 12 tombs including eye-beads, rings and ear pendants. Eight samples were selected covering all shapes in Xinfeng glass wares were observed by polarizing optical microscopy and analysed by scanning electron microscopy (SEM) equipped with energy dispersive X-ray analysis (EDX) as well as micro-Raman spectrometer. The chemical composition showed there are one potassium ear pendant glass, one faience bead with potassium-calcium glaze layers and six lead-barium glass of all the shapes mentioned above. The coloring agent for the blue wares is copper and copper allied with iron for the green wares.
The results indicate the obvious increasing on melting temperature during the Warring States to the Eastern-Han dynasty, and this might reflect the development of thermo-technology, such as the use of more efficient fuel etc. The chemical analyses also suggest that lead-barium glass wares in Xinfeng cemetery might have different recipes or origins. Thus, it has been concluded that there might have existed several manufacturing centers no later than the Eastern-Han dynasty supplying the glass wares used in the Xinfeng area. However according to the low ratio of discovery of glass artifacts in the tombs, the glass should be regarded as precious procession only owned by the few people in the Xinfeng areas despite the multiple manufacturing centers available.
9:00 PM - TC3.9.14
Removing Pollutants from Indoor Atmosphere—Green Synthesis of New Generation of Visible Light Photocatalizers
Enrico Greco 1 , Enrico Ciliberto 1 , Jing Shang 2 , Donatella Capitani 3 , Valeria Di Tullio 3
1 Department of Chemical Sciences University of Catania Catania Italy, 2 College of Environmental Sciences and Engineering Peking University Beijing China, 3 Institute o Chemical Methodologies Consiglio Nazionale delle Ricerche Rome ItalyShow Abstract
Very often, inside exposition areas, the atmosphere quality is greatly affected by pollutants species derived from both extrinsic reasons (visitors etc.) and intrinsic reasons such as the decomposition products of the artifacts, in particular if they are constituted by organic materials. These species are responsible of secondary processes of degradation and represent a real risk for the conservation of the artifacts themselves. The route towards removing these species with photocatalytic reactions is not easy because, generally, photocatalysts operates in the range of ultraviolet light that, obviously cannot be used in museum areas for its property of damaging the materials, in particular the organic ones.
This work focuses on a new sol-gel synthesis method of different doped titanium dioxide nanoparticles with optimal photocatalytic performance in the visible range of light. The synthesis fulfills the criteria of cost and can be carried out without the use of organic solvents or high-temperature treatments.
The new sol–gel method of synthesis of TiO2 anatase reported in this work used titanium tetrabutoxide as the precursor, lithium(I), cobalt(II) and cerium(IV) salts as dopant species. By controlling the hydrolysis of the precursor, the dopant concentrations and the rate of drying under vacuum, doped anatase nanoparticles in the range between 10 and 90 nm, and transparent xerogel were obtained at room temperature.
The morphology and the microstructure of doped anatase samples were investigated by SEM, HRTEM, BET, XRD, Raman spectroscopy, XPS and EXAFS methods. The band gap of the doped photocatalysts were estimated by solid-state UV–Vis spectrophotometer and several tests were carried out in heterogeneous phases (oxidation of Rhodamine B and degradation of Formaldeide gas), both with colorimetric measurements and gas chromatographic analyses, in order to evaluate the catalyst efficiency in the photo oxidation processes. The mobility of Li+ ions on TiO2 NPs surface was also studied by 7Li MAS NMR spectroscopy.
Fifteen different materials were made and the best performance under visible light were detected using lithium and cobalt as dopants at 1% and 5%, respectively.
Aaron Shugar, SUNY - Buffalo State
Stavroula Golfomitsou, UCL Qatar
Chandra Reedy, Univ of Delaware
Pamela Vandiver, Univ of Arizona
Society for Archaeological Sciences, XGLab and nSynergies
TC3.10: Non-Destructive, High-Precision, High-Resolution Characterization of Works of Art
Friday AM, December 02, 2016
Sheraton, 3rd Floor, Fairfax B
9:00 AM - TC3.10.01
The Application of the LIBS Technique to Quantify Boron in Chinese Low Temperature Glazes
Hongying Duan 1 , Liang Qu 1 , Xinqiang Zhang 2
1 Conservation Department of the Palace Museum Beijing China, 2 Beijing Institute of Technology Beijing ChinaShow Abstract
The manufacture and firing of low temperature glazes has a long history in China. In the Qing Dynasty (1644-1912 C.E.), low-temperature lead-containing glazes were used as overglaze enamels to decorate porcelain. These brilliant fritted glass colors were developed into many different color palettes and styles, such as famille rose (fencai), doucai, and the directly applied falangcai glazes. These stylistically distinctive and innovative technologies led to new products that were highly prized, and many exquisite porcelain products were successfully fired and are now preserved in museums. Simultaneously, low-temperature enamels were also developed for coating fabricated metal vessels. In previous work, we speculated that the raw materials, manufacturing technology and interactions among artisans and potters occurred, such that knowledge may have been shared. We also speculated that the low-temperature glazes may have contained the element boron as a significant constituent. Boron has been the focus of several scholars because of its importance to better understand the selection and use of raw materials, to investigate compositional variability, and to correlate communities of technological practices. Boron, being a light element, is difficult to detect by most elemental analytical techniques (e.g., XRF, EPMA, etc.). Laser-induced-breakdown spectroscopy (LIBS) is an emerging method of analysis that provides an effective solution to detect low atomic number elements, such as boron. LIBS has the advantages for precious museum collections that it requires no sample preparation and can be conducted on-site without removal to a laboratory setting. We established a quantitative calibration curve for boron using boron-containing glass standards. Then we analyzed overglaze enamels on glazed porcelain and metal bodies: including famille rose (fencai), doucai, enamel glaze or falangcai, and metal-body glaze samples, including: cloisonne enamels (qiasifalang), champleve enamels (zantaifalang) and painted enamels (huafalang) of the Qing Dynasty in the Palace Museum collections. The boron contents also were measured and calculated with other analytical methods. The compositions and raw materials of these low-temperature glazes were studied and their technological development will be summarized, and connections among the manufacture technologies will be discussed.
9:15 AM - TC3.10.02
Characterizing the Age of Ancient Egyptian Manuscripts through Micro-Raman Spectroscopy
Sarah Goler 1 , James Yardley 1 , Angela Cacciola 1 , Alexis Hagadorn 2 , David Ratzan 3 , Roger Bagnall 3
1 Columbia Nano Initiative Columbia University New York United States, 2 Columbia University Libraries Columbia University New York United States, 3 Institute for the Study of the Ancient World New York University New York United StatesShow Abstract
We have established scientific basis for a new, non-destructive methodology for dating ancient Egyptian papyri based on Raman spectroscopy. Egypt’s dry climate has preserved thousands of handwritten documents which provide insight into ancient cultures, but most of these manuscripts are not dated. Currently, the only scientific method for estimating the date is radiocarbon dating, which is destructive and cannot be used to date the ink separate from the support. In contrast, micro-Raman spectroscopy, a non-destructive light scattering technique, can distinguish physical and chemical properties of materials. We discovered, for a study of well-dated ancient Egyptian papyri covering the date range from 300BCE to 900CE, the Raman spectra (25-40 measurements per manuscript) of black ink all show the spectrum of carbon black characterized by two broad features, the G- and D-bands indicative of crystalline and amorphous carbon. The G-band, 1585cm-1, is a Raman allowed transition arising from the E2g in-plane vibration of sp2-bonded carbon. The D-band at ~1350cm-1 is a forbidden Raman transition that occurs when the lattice symmetry is broken due to disorder, vacancies, crystalline edges, etc. We observed the spectra exhibit systematic change as a function of manuscript date, unexpected given these papyri span 1,200 years and the fact that each manuscript has a unique provenance, archeological, and storage history. We conclude Egyptian black ink pigments were manufactured using similar processes over this time-period. We attribute the systematic changes in Raman spectrum to two concurrent oxidation processes: slow oxidation of crystalline carbon and faster oxidation of amorphous carbon. Oxidative degradation proceeds over time altering the Raman response of the material, providing a direct experimental indicator for manuscript age. This research establishes the basis for a simple, rapid, non-destructive method for dating ancient manuscripts from Egypt as well as the ability to differentiate between modern forgeries and authentic ancient manuscripts.
9:30 AM - TC3.10.03
Probing Microstructure and Chemistry from the Sub-Micron to the Atomic Scale to Reveal Raw Materials Selection in the Production of Egyptian Blue and Chinese Blue Pigments
Yuan Lin 1 2 , Gilles Patriarche 3 , Matthew Marcus 4 , Guofeng Wei 5 , Xiao-Juan Huang 6 , Philippe Walter 7 , Ioanna Kakoulli 1 2 8
1 Materials Science and Engineering Department University of California, Los Angeles Los Angeles United States, 2 Molecular and Nano Archaeology Laboratory University of California, Los Angeles Los Angeles United States, 3 Laboratoire de Photonique et Nanostructures Centre National de la Recherche Scientifique Marcoussis France, 4 Advanced Light Source, Lawrence Berkeley National Laboratory Berkeley United States, 5 Department of History Anhui University Hefei China, 6 Archaeological Institute of Shaanxi Province Xi'an China, 7 Laboratoire d’Archéologie Moléculaire et Structurale, UMR 8220 CNRS Université Pierre et Marie Curie Paris France, 8 UCLA/Getty Conservation Program, Cotsen Institute of Archaeology University of California, Los Angeles Los Angeles United StatesShow Abstract
The manufacture of vitreous materials represents a significant technological achievement in antiquity. These include glazed stones, faience, glass, ceramics, as well as synthetic pigments such as Egyptian blue (CaCuSi4O10) and Chinese blue (BaCuSi4O10). Egyptian blue (EB) and Chinese blue (CB) are two highly stable synthetic copper silicate pigments first produced in the Old Kingdom of Egypt (3rd millennium BC) and the Western Zhou period (1046-771 BC) respectively. They are composed of three distinct phases: an isostructural-layered square planar crystalline copper silicate phase; interstitial glass and residual quartz. However, despite their abundance, there are no comprehensive recipes for their production and the geological origins of the raw materials used are still unknown. Previous studies focused in understanding the processes of production and gaining an insight into the type of raw materials employed in the synthesis of the two pigments. Suggested possible raw materials include: 1) Source of Cu: malachite (Cu2(CO3)(OH)2), azurite (Cu3(CO3)2(OH)2), smelted Cu, or reused bronze; 2) Source of silica: sand or quartz pebble; 3) Source of Ca (in EB): sand or limestone; 4) Source of Ba (in CB): barite (BaSO4) or witherite (BaCO3); and 5) Source of flux: natron (NaCO3 and NaHCO3), galena (PbS), lead oxide (PbO) or cerussite (PbCO3) and reused leaded bronzes. However, due to analytical challenges posed mainly by limitations of traditional laboratory-based techniques, still lacking is an in depth analysis of key elements in the manufacture of EB and CB inferring craft specialization and intra and inter-regional trade of materials. In order to fill the gap in current understanding of identities and geological origins of raw materials selected for the production of EB and CB, this research focuses on the characterization of interstitial glass (both soda-lime and lead-rich) and microscopic residual crystalline byproducts of which structural information and isotopic signatures could provide crucial information in understanding processes of production and raw materials selection. Minimally invasive techniques with high-resolution, high-precision and high-accuracy were applied, including scanning transmission electron microscopy coupled with energy dispersive x-ray spectroscopy (STEM-EDS), synchrotron radiation-based X-ray fluorescence spectromicroscopy (SR-μXRF), synchrotron radiation-based micro-X-ray absorption near edge structure (SR-μXANES), and multiple collection-laser ablation-inductively coupled plasma-mass spectrometry (MC-LA-ICP-MS).
9:45 AM - TC3.10.04
Specular Reflection FTIR—A Non-Contact Method for Analyzing Surface Coatings on Historic Photographs
Arthur Mcclelland 1 , Elena Bulat 2 , Erin Murphy 2 , Brenda Bernier 2
1 Center for Nanoscale Systems Harvard University Cambridge United States, 2 Weissman Preservation Center Harvard University Cambridge United StatesShow Abstract
In 1839, William Henry Fox Talbot introduced the salted paper print technique. Salted paper prints do not have an emulsion. Because the image particles are distributed in the uppermost layers of the paper fibers, the prints exhibit a matte surface. Photographers often applied a thin clear coating to their salted paper prints. The coating served an aesthetic function as it filled in the tiny areas created by the paper fibers to create a rich, saturated appearance and also as a protective coating. A variety of materials were used at the time. Characterization of photographic coatings is an important tool for dating and identifying individual photographs, contributing new scholarship to our understanding of the history of photography and making preservation decisions.
The Weissman Preservation Center at Harvard Library has undertaken a multiyear project which seeks to enhance our understanding of salted paper prints and to ensure their long-term preservation. The majority of the estimated 8,000 salted paper photographs at the Harvard University Archives reside in 75 historic class albums dating from 1852 to 1864, as well as in a large collection of loose prints which are duplicates or variants of those in the albums. The class albums were produced annually over a period of 13 years by three prominent Boston photographers; John Adams Whipple, James Wallace Black and George Kendall Warren. These class albums provide a glimpse into the technical evolution of the salt print process as practiced by some of Boston’s pioneering photographers.
Specular reflection FTIR was used as a non-contact, non-sampling chemical analysis technique for the coatings on the salted paper prints. Most FTIR spectral libraries do not contain specular reflection spectra. A specular reflection FTIR spectral reference library was created for this project using modern samples of the possible salted paper print coatings. This new spectral reference library and the specular reflection FTIR technique allowed for the positive identification of the coatings used in the historic Harvard class albums.
10:00 AM - TC3.10.05
X-Ray Spectroscopy Investigation of Modern Oil Paints
Anna Regoutz 1 , Judith Lee 2 , Bronwyn Ormsby 2 , David Payne 1
1 Imperial College London London United Kingdom, 2 Tate Britain London United KingdomShow Abstract
A detailed knowledge of the surface chemistry of a painting can be crucial to the success of conservation procedures. Even simple surface cleaning treatments can face unexpected complications due to unwanted reactions with chemical species present on the surface of a painting. Often, these species form over time by interaction of the paint with moisture, air or light, and are not initially part of the paint formulation. A problem widely faced in the conservation of twentieth-century oil paintings for example, is their sensitivity to aqueous swabbing, which is routinely used to clean the surface of unvarnished oil painting. It has been reported to affect a number of modern oil paintings, including works from Karel Appel, Jasper Johns, and Robyn Denny.
X-ray photoelectron spectroscopy (XPS) is a method used widely in the solid-state and surface sciences. It has the unique ability to provide surface-sensitive, non-destructive measurements of a wide variety of samples. Due to the outstanding surface sensitivity of XPS, with an escape depth of 1-4 nm, even small amounts of surface species can be detected and are not overshadowed by bulk contributions. Careful data analysis based on peak fitting delivers both quantitative and qualitative results. Through chemical shifts in core level data oxidation states of metals and chemical states of e.g. C can be identified.
This work presents XPS analysis of two paints by Winsor & Newton which react differently when exposed to water: French Ultramarine (water sensitive) and Flake White (insensitive to water). Small samples taken from paint swatches of two different ages were analysed. Early samples stem from 1949 (French Ultramarine) and 1957 (Flake White) whilst the newer samples are from 2003. Data from both the surface as well as the bulk (from fracturing) of the paint fragments were collected. Quantitative analysis shows large differences between the elemental distribution at the surface and in the bulk of the paint chips as well as between samples of different ages. To analyse the chemical states of the elements present, both core level and Auger line spectra were collected. Changes in the oxidation state of lead are found in Flake White as well as distinct differences in the C and O 1s core levels of the French Ultramarine pointing towards changes in the oil component of the paints. Furthermore, the influence of the paper used for the paint swatches is analysed.
Ultimately, these experiments present an in-depth characterisation of the surface and bulk chemistry of two widely used oil paints and show the great potential of applying XPS to paint conservation topics. The analysis results provide conservationists with a comprehensive knowledge base of the surface chemistry, in particularly identifying and quantifying species not part of the original paint formulation. This knowledge can be used to develop new cleaning techniques preventing negative interactions with such unexpected surface species.
10:15 AM - TC3.10.06
Non-Destructive Characterization of Archaeological Egyptian Turquoises in The Metropolitan Museum of Art
Brunella Santarelli 1 , Federico Caro 1 , Deborah Schorsch 2
1 Department of Scientific Research The Metropolitan Museum of Art New York United States, 2 Objects Conservation Department The Metropolitan Museum of Art New York United StatesShow Abstract
Turquoise, an opaque blue-green hydrated copper aluminum phosphate mineral, was greatly valued throughout the ancient world. This was particularly the case in Egypt, where some of the oldest known turquoise mines are located in southwest Sinai. Turquoise was the objective of royal expeditions dispatched to the Sinai that are documented in ancient texts, and is attested to by the temple at Serabit el-Khadim dedicated to the goddess Hathor—the Lady of Turquoise—near the ancient mines. This paper presents the results of a research project carried out at The Metropolitan Museum of Art aimed at characterizing the composition and mineralogy of turquoise from archaeological contexts in Egypt.
Turquoise has been used as a proxy to study trade networks and other interaction and exchange mechanisms. Most of the analytical studies sourcing archaeological turquoise, however, have focused on the American Southwest and Mexico, and the different destructive methodologies used to source these stones are inappropriate for very small antiquities found in museum collections. A non-destructive approach using X-ray fluorescence (XRF) spectroscopy has shown great potential for establishing compositional and geological variability of Egyptian turquoises. Comparison of these materials to raw turquoise from mines in Egypt, and from Near Eastern archaeological and geological contexts, has the potential for addressing questions of sourcing, trade, and authenticity for artifacts associated with these regions. In addition to the compositional and geological characterization of turquoise, this investigation has proved useful in distinguishing between turquoise, feldspar, and beryl, all of which are represented in the Egyptian collection, but often incorrectly identified. The corrected identifications provide valuable information regarding mineral usage during different historical periods in ancient Egypt.
TC3.11: Development of Adhesives/Consolidants Used in Archaeology and Conservation
Friday PM, December 02, 2016
Sheraton, 3rd Floor, Fairfax B
11:00 AM - *TC3.11.01
Consolidating Adhesive Project
Rebecca Ploeger 1
1 State University of New York College at Buffalo Buffalo United StatesShow Abstract
The consolidating adhesive project is an international collaboration which aims to develop a new adhesive specific for the consolidation of painted layers. Since starting in 2010, many interesting findings have been made, and new polymer-tackifier, and polymer-tackifier- wax blends, have been tested. The concept of component miscibility, and the effect it has on the final properties of the adhesive, is complex but fundamental to the development of a new product. To quantify the properties conservators most need, the initial focus was on understanding BEVA® 371, a widely used poly(ethylene vinyl acetate) based heat-seal adhesive. It was originally developed as a lining adhesive for paintings, and has been adapted by conservators for a variety of consolidating applications. However, its ideal consolidation performance properties are starting to be out-weighed by concerns regarding its long-term stability, as well as a formulation change. There is a need for a new adhesive tailored to the requirements of the conservation field. This paper will discuss the results obtained thus far, and the goals for the future. The project is entering a new phase, where we hope to continue to explore new blends, and have conservator testing on painting mock-ups.
11:30 AM - TC3.11.02
Acrylic-Based Mortar for Sandstone Repair—A Viscoelastic Analysis of the Thermal Stresses
Thibault Demoulin 1 , George Scherer 2 , Fred Girardet 3 , Robert Flatt 1
1 Institute for Building Materials ETH Zurich Zurich Switzerland, 2 Department of Civil and Environmental Engineering Princeton University Princeton United States, 3 RINO Sarl Blonay SwitzerlandShow Abstract
In historical buildings, repair of altered stone using mortar is an attractive strategy, when it avoids the full replacement of the original stone and extends its lifetime. However, the stresses that could arise due to a mismatch of dimensional changes (thermal expansion or hygric/hydric swelling) between the repair layer and the stone substrate might significantly reduce the durability of the repair and affect the historical material.
In this study we analyze the magnitude of the thermal stresses that originate in an acrylic-based repair mortar used for the reprofiling of natural sandstone. In this repair mortar, the binder of the sandstone, calcium carbonate, is replaced by an acrylic polymer. This kind of artificial stone was developed in the late 70’s in the Ecole Polytechnique Fédérale de Lausanne (EPFL, Switzerland) for its peculiar properties of reversibility in an organic solvent and its easy adaptation to the stone color. However, it possesses a high thermal expansion, together with time- and temperature-dependent mechanical properties, which might expose the stone that it aims to repair to high thermal stresses.
To evaluate this risk we propose an analytical solution that considers the viscoelasticity of the repair layer. Since the stresses are highly dependent on the heating and cooling rate, the temperature profile used in the numerical evaluation has been measured in the Catholic Church of Notre-Dame de Vevey (Switzerland), where the artificial stone has been used in a restoration campaign. The viscoelastic behavior of the artificial stone has been characterized by stress relaxation experiments at different temperatures in the laboratory. The study reveals that the glass transition temperature of the polymer is within the range of temperature found on-site. This allows a periodic relaxation of stresses. Moreover, the numerical analysis shows that the relaxation time of the repair mortar allows relief of most of the stresses that develop due to the thermal expansion coefficients mismatch. In conclusion, we show that viscoelastic relaxation accounts for the durability of this particular repair material, as observed by the practitioners.
11:45 AM - TC3.11.03
(Ca, Ba)(OH) 2 Based Nanoparticles with Tunable Chromatic Properties and Their Applications for In Situ Desalination and Consolidation of the Sandstone Monuments
Ke Liu 1 , Renfa Guan 1 , Ya Xiao 1 2 , Weiqiang Zhou 3 , Kaiyu Liu 4 , Shaojun Liu 1
1 Powder Metallurgy Research Institute Central South University Changsha China, 2 Cultural Relics and Archaeology Institute of Hunan Changsha China, 3 Shanxi Provincial Institute of Cultural Heritage Xi'an China, 4 School of Chemistry and Chemical Engineering Central South University Changsha ChinaShow Abstract
It is well known that the hydration and dehydration of sulfur-containing soluble salt are considered as one of the most important factors to decay the outdoor sandstone monuments. Although supersaturated Ba(OH)2 solution combined with (NH4)2CO3 has been shown to reduce the content of sulfur-containing soluble salt by forming insoluble BaSO4 salt, it is poisonous and corrosive. In this study, we reported on the synthesis of novel (Ca, Ba)(OH)2 based nanoparticles by conventional chemical co-precipitation method with tunable size and chromatic properties and the evaluation for in-situ desalination and consolidation of the decayed stone. They were further characterized by X-rays diffractometer, scanning electron microscopy, Fourier transform infrared spectroscopy, and Brunauer-Emmett-Teller (BET) measurement. XRD results show that the solubility of barium in Ca(OH)2 nanoparticles is below 15%. The particle size of Ca(OH)2 nanoparticles is ~50nm. It can significantly reduce to ~16nm by doping 15% barium. Ion chromatograph measurement shows that the SO42- ions in artifially decayed sandstones can be effectively fixed, evidenced by significantly decreased concentration of SO42- ions from 4.9mg/g to 0.84mg/g for sandstones treated by Ca0.85Ba0.15(OH)2 nanoparticles dispersion. Especially, its compressive strength significantly increases to 38.98MPa from 26.64MPa. It is further shown that the chromatic properties of consolidated sandstone can be tuned by using Ni doped (Ca, Ba)(OH)2 nanoparticles. The chromatic change for stones treated by undoped nano (Ca, Ba)(OH)2 is 4.59. In contrast, it significantly decreases to ~1.2 and ~0.6 for 5% and 1% Ni-doped (Ca, Ba)(OH)2 nanoparticles, respectively. With good compatibility and weatherability, as-synthesized (Ca, Ba)(OH)2 based nanoparticles shows promising applications for in-situ desalination and consolidation of sandstone or mortars monuments.
12:00 PM - TC3.11.04
Optimization of the Consolidation of Swelling Clay-Bearing Sandstones through Design of Experiment (DOE)
Ylenia Pratico 1 , Timothy Wangler 1 , Francesco Caruso 1 , Robert Flatt 1
1 ETH Zurich Zurich SwitzerlandShow Abstract
Sandstones containing swelling clays are particularly susceptible to degradation phenomena associated with cycles of wetting and drying. For this reason, practitioners dealing with this type of material have to face critical conservation questions, including whether or not to apply a consolidation treatment.
This issue is widely encountered in the Swiss plateau, where most natural building stones in historical structures contain swelling clays, but is also present in the northeastern United States, where Portland Brownstone is commonly found in historical buildings dating from the XVII century.
Generally, ethyl-silicates(TEOS)-based products are the most accepted choice in terms of consolidation treatments for stone. However, their effectiveness is believed to be influenced by environmental factors such as temperature and humidity, as well as by the application procedure followed.
Furthermore, it has been shown that TEOS-based treatments applied on clay-bearing sandstones may lose their effectiveness after few wetting/drying cycles, and it has been suggested that a pre-treatment with swelling inhibitors could enhance their durability.
All these variables are difficult to control on-site, and make it hard for practitioners to define an optimal conservation strategy for each case scenario.
With our work, we use the statistical method of Design of Experiment (DOE) to study – with a limited number of experiments – the combined effect of a range of factors on the final success of the consolidation treatment, allowing for an optimization of the conservation strategy under the given conditions.
In particular, we analyzed the concurrent effect of temperature, relative humidity, application procedure and pre-treatment with a swelling inhibitor on the consolidation of a Swiss swelling clays-bearing stone, the molasse of Villarlod.
The effects of these factors on the consolidation treatment were evaluated in terms of changes in dynamic elastic modulus (Edyn), measured by means of Ultrasonic Pulse Velocity Measurements (UPVM). The final increase in Edyn is taken as an indication for the total consolidation effect, while the time needed to reach this value is defined as the curing time.
Our results show that the total consolidation is not affected by temperature, humidity or the application method. On the other hand, the curing time is strongly influenced by the above-mentioned factors. In particular, it is shown that higher initial moisture content is beneficial to the consolidation treatment as it significantly shortens the curing time.
12:15 PM - TC3.11.05
Analytical Observations Regarding Butvar B98 and Paraloid B72 Blends as a Suitable Adhesive in Hot Climates
Paige Schmidt 1 , Aaron Shugar 1 , Rebecca Ploeger 1
1 State University of New York College at Buffalo Buffalo United StatesShow Abstract
An adhesive that can withstand elevated temperatures is necessary for the conservation of artifacts in hot climates. The use of Butvar B98 as a modifier to raise the glass transition temperature of Paraloid B72 was investigated. The characteristics of Paraloid B48n and B72 blends, currently in use in the field of conservation, were used as a comparison for analysis of the Butvar B98 and Paraloid B72 blends. Differential Scanning Calorimetry (DSC) was used to determine the glass transition temperatures of the blends and tensile testing was used to investigate the tensile strength of the blends. While the Butvar B98 and Paraloid B72 blends attained elevated glass transition temperatures and performed well during tensile testing, issues regarding miscibility and phase separation of the blends were investigated using transmission FTIR, DSC, and optical microscopy.