Herant Khanjian

Application of chemical and thermal analysis methods for studying cellulose ester plastics.

Cellulose acetate, developed about 100 years ago as a versatile, semisynthetic plastic material, is used in a variety of applications and is perhaps best known as the basis of photographic film stock. Objects made wholly or partly from cellulose acetate are an important part of modern and contemporary cultural heritage, particularly in museum collections. Given the potential instability of the material, however, it is imperative to understand the aging mechanisms and deterioration pathways of cellulose ester plastics to mitigate decomposition and formulate guidelines for storage, exhibition, and conservation. One important aspect of this process is the ability to fully characterize the plastic, because variations in composition affect its aging properties and ultimate stability. In this Account, we assess the potential of a range of analytical techniques for plastics made from cellulose acetate, cellulose propionate, and cellulose butyrate. Comprehensive characterization of cellulose ester plastics is best achieved by applying several complementary analytical techniques. Fourier-transform IR (FTIR) and Raman spectroscopy provide rapid means for basic characterization of plastic objects, which can be useful for quick, noninvasive screening of museum collections with portable instruments. Pyrolysis GC/MS is capable of differentiating the main types of cellulose ester polymers but also permits a richly detailed compositional analysis of additives. Thermal analysis techniques provide a wealth of compositional information and thermal behavior. Thermogravimetry (TG) allows for quantitative analysis of thermally stable volatile additives, and weight-difference curves offer a novel means for assessing oxidative stability. The mechanical response to temperature, such as the glass transition, can be measured with dynamic mechanical analysis (DMA), but results from other thermal analysis techniques such as TG, differential scanning calorimetry (DSC), and dynamic load thermomechanical analysis (DLTMA) are often required to more accurately interpret the results. The analytical results from this study form the basis for in-depth studies of works of art fabricated from cellulose acetate. These objects, which are particularly at risk when stored in tightly sealed containers (as is often the case with photographic film), warrant particular attention for conservation given their susceptibility toward sudden onset of deterioration.

Gas Chromatographic Analysis of Amino Acids as Ethyl Chloroformate Derivatives. Part 2, Effects of Pigments and Accelerated Aging on the Identification of Proteinaceous Binding Media

AbstractProteinaceous binding media present in paintings can be identified by gas chromatographic analysis of the ethyl chloroformate derivatives of amino acids. The effects of pigments on the amino acid composition data of hydrolyzed gelatin that were obtained by this method were studied. The method was also used to analyze glue and egg tempera paint films that were exposed to heat and light in order to accelerate the aging of the paints. Pigments and accelerated aging were found to affect the concentrations of all amino acids, although the concentrations of alkyl and imino-substituted amino acids were affected to a much smaller degree than others. Samples of grounds and paints that were removed from a number of paintings and painted objects were analyzed by this method. The proteins present in the samples were identified from the amino acid molar percentages by correlation to published amino acid composition data.

Gas Chromatographic Analysis of Amino Acids As Ethyl Chloroformate Derivatives. Part 1, Composition of Proteins Associated with Art Objects and Monuments

AbstractGas chromatography has long been used as a means of identifying proteins in acid hydrolysates of paints and adhesives on the basis of their amino acid composition. Existing procedures for amino acid derivatization can, however, take up to 4 hours per analysis, whereas a new procedure employed at the Getty Conservation Institute can be carried out in less than 20 minutes. This procedure involves the formation of N(O,S)-ethoxycarbonyl ethyl esters of amino acids using ethyl chloroformate and then a separation on an HP-INNOWAX capillary column. This procedure was employed to analyze samples from the binding media library at the Getty Conservation Institute, and amino acid compositions were tabulated for various proteins that could be used for identification purposes.

Some observations on the composition of Chinese lacquer

This paper summarizes the various information that has been gathered in recent years at the J. Paul Getty Museum and Getty Conservation Institute with regard to the organic constituents of Chinese lacquer formulations. While this summary of materials is by no means comprehensive or complete, it captures the current state of the authors’ knowledge, with the information itself and the bibliography intended to serve as a useful foundation from which further research may proceed. Considerable advances have been made in the last decade in the technique of pyrolysis-gas chromatography–mass spectrometry with thermally assisted hydrolysis and methylation using tetramethylammonium hydroxide and in subsequent data interpretation methodologies. These have dramatically improved the sensitivity and specificity of organic analysis. Perhaps equally important, these methodologies are allowing researchers to collaborate much more effectively and to share results that are truly comparable and reproducible. As more researchers participate and collaborate, and as more results are aggregated into shared databases, significant new insights into the methods and materials of Chinese lacquer are sure to follow.

Chinese lacquer: Much more than Chinese lacquer

A significant portion of Asian lacquer collections in today’s western museums was originally made in China specifically for export to European markets. The J. Paul Getty Museum’s collection includes pieces of French furniture dating to the mid-eighteenth century that incorporate panels of Chinese export lacquer as part of their surface decoration, an early eighteenth-century inkstand thought to be of Ryukyuan origin (76.DI.12), an eighteenth-century secretaire (65.DA.3), and an eighteenth-century black lacquered cupboard (78.DA.119). In a systematic technical study of these lacquered objects, analysis of the organic constituents in individual lacquer layers was carried out using pyrolysis – gas chromatography – mass spectrometry with tetramethylammonium hydroxide derivatization (THM‒ Py‒GC‒MS) [1–3]. Additionally, the presence of protein, oil, and starch within the layer structure of lacquer cross sections was visualized with both visible and blue light illumination after treatment with selected stains used in histochemical protocols [4]. As the research progressed, objects from other museum collections were studied for comparative purposes in order to gain a broader understanding of temporal and geographic trends in Chinese lacquer formulation. It had been assumed that all Chinese qi lacquerware was made from urushiol, which is the exudate of Toxicodendron verniciflua trees that grow throughout specific regions of China, Japan and Korea. However, this study revealed that Chinese export lacquered objects were formulated with laccol, which is the exudate from Toxicodendron succedaneum. 現今西方博物館收藏的亞洲漆器,有大部份是中國

Colorimetric sensor arrays: development and application to art conservation

ABSTRACT Acceptable air pollutant concentration limits for sensitive artwork are generally at or below a few ppb: this is only ∼1% of the permissible exposure limits for humans. Monitoring pollutants at such low levels is an exceptional challenge, especially to do so in a cost-effective fashion for a large number of locations and microenvironments (e.g., every display case in a museum). To meet this challenge, we have extended our portable “optoelectronic nose,” by using new sensor array chemistry to develop cumulative colorimetric sensor arrays with dosimetric sensitivities that are dramatically better than commercial sensor tubes. The color changes of each sensor in a disposable printed array produce a composite response to volatiles. Using cell phone camera imaging, we have made field trials to monitor pollutant exposure of artwork from the Walt Disney Animation Research Library during shipping to and exhibition in Beijing. This exhibition, “Drawn from Life: the Art of Disney Animation Studios,” featured animation drawings, story sketches, layouts, and concept art spanning the 90 years of the Disney Animation Studio’s history. Sensor arrays monitored exterior and interior environments of passe-partout artwork frames during exhibition and inside shipping crates during transport providing quantitative information on oxidant, aldehyde, and sulfide pollutant exposure.

The early use of synthetic emulsion paints by New Zealand artists

Abstract The 1960s in New Zealand saw a different approach to painting that was linked to an exploration of new materials and ways of using them. New synthetic emulsion paints had become available with properties quite distinct from traditional oils, and many artists chose to use them. Their versatility and ease of use appeared to provide further liberation from the past methodologies and also allowed them to focus on the image. A study looking at the early use of polyvinyl acetate (PVA or PVAc) and acrylic paints by New Zealand artists from the collections of the Auckland Art Gallery Toi o Tamaki and Museum of New Zealand Te Papa Tongarewa forms the basis of the findings presented in this paper. Paintings from the collections were surveyed including detailed examination of 16 works. Primary sources were a large part of the study including artist interviews, letters and other archival material. Samples from the paintings were analysed with FTIR and Py-GC/MS. A majority of the paintings were found to have PVA or PVA/2-EHA copolymers and only a minority were painted solely in acrylic. Many of the paintings included a variety of media, including oil or alkyd.