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Harvard, MA, United States

Kirby D.P.,Straus Center for Conservation | Buckley M.,University of Manchester | Promise E.,Harvard University | Trauger S.A.,Center for Systems Biology | Holdcraft T.R.,Harvard University
Analyst | Year: 2013

All stakeholders in cultural heritage share an interest in fabrication methods and material technology. Until now methods for analysis of organic materials, particularly proteins, have not been widely available to researchers at cultural institutions. This paper will describe an analytical method for the identification of collagen-based materials from soft tissue sources and show examples of its application to diverse museum objects. The method, peptide mass fingerprinting (PMF), uses enzymatic digestion of extracted proteins to produce a mixture of peptides. The mass spectrum of the mixture contains characteristic marker ions - a peptide mass fingerprint - which are compared to species-specific markers from references as the basis of identification. Preliminary results indicate that analysis of materials from aged samples, several different tissue types, and tanned or untanned materials yields comparable PMF results. Significantly, PMF is simple, rapid, sensitive and specific, has been implemented in a museum laboratory, and is being practiced successfully by non-specialists. This journal is © The Royal Society of Chemistry. Source


News Article | March 21, 2016
Site: http://www.fastcompany.com

Today, every color imaginable is at your fingertips. You can peruse paint swatches at hardware stores, flip through Pantone books, and fuss with the color finder that comes with most computer programs, until achieving the hue of your heart's desire. But rewind to a few centuries ago and finding that one specific color might have meant trekking to a single mineral deposit in remote Afghanistan—as was the case with lapis lazuli, a rock prized for its brilliant blue hue, which made it more valuable than gold in medieval times. The history of pigments goes back to prehistoric times, but much of what we know about how they relate to the art world comes from Edward Forbes, a historian and director of the Fogg Art Museum at Harvard University from 1909 to 1944. Considered the father of art conservation in the United States, Forbes traveled around the world amassing pigments in order to authenticate classical Italian paintings. Over the years, the Forbes Pigment Collection—as his collection came to be known—grew to more than 2,500 different specimens, each with its own layered backstory on its origin, production, and use. Today, the collection is used mostly for scientific analysis, providing standard pigments to compare to unknowns. Narayan Khandekar is the director of the Straus Center for Conservation and Technical Studies at the Harvard Art Museums and the collection's custodian. For the last 10 years, Khandekar has rebuilt the collection to include modern pigments to better analyze 20th century and contemporary art. A lot has changed in the art world since painters worked with "colormen"—as tradesmen in dyes and pigments were known—to obtain their medium. The commercialization of paints has transformed that process. "Artists today will use anything to get the idea that's in their head into a physical form," Khandekar says. "It could be pieces of plastic. It could be cans of food. It could be anything. We need to be able to identify lots of different materials that are industrially produced as well as things that are produced specifically for artists' use." The way he describes his work researching and cataloging pigments is akin to detective work. "We use our instruments in the same way that forensic scientists do," Khandekar says. "We examine and find out what we can about the key compounds that will tell us the material's origin." But instead of tools such as DNA analysis, he and his team of conservation scientists use techniques such as Raman spectroscopy, mass spectrometry, gas chromatography, and electron microscopy to map out the precise chemical composition of a pigment. For example, their work was instrumental in proving that a Jackson Pollock painting "rediscovered" in 2007 was actually a fake, after pigment analysis revealed that a specific red color was manufactured 20 years after the artist's death. The color, Red 254, was a by-product of a chemical reaction first documented in 1974; it's also nicknamed "Ferrari red." "Every pigment has its own story," Khandekar says. With that in mind, we asked him to share the stories of 10 of the rarest and most interesting pigments in the Forbes collection. Synthetic Ultramarine "This was discovered in 1826 as the result of a contest. In a way it is like discovering how to make gold as artists no longer had to buy natural ultramarine at great cost." Mummy Brown "People would harvest mummies from Egypt and then extract the brown resin material that was on the wrappings around the bodies and turn that into a pigment. It's a very bizarre kind of pigment, I've got to say, but it was very popular in the 18th and 19th centuries." Brazilwood "Brazilwood is any of several tropical trees of the senna genus. Its hard, red-color wood has had limited use for violins, bows, veneer, and high-quality furniture. The wood contains the colorant brasilin, which gives a deep-red to brownish color. Brazilwood dye has been used for textile and leather dyes, inks, paints, varnish tints, and wood stains." Quercitron "A yellow vegetable dye, quercitron is extracted from the black or dark brown bark of the black oak, Quercus velutina, that is native to the Eastern and Midwestern parts of the United States." Annatto "The lipstick plant—a small tree, Bixa orellana, native to Central and South America—produces annatto, a natural orange dye. Seeds from the plant are contained in a pod surrounded with a bright red pulp. Currently, annatto is used to color butter, cheese, and cosmetics." Lapis Lazuli "People would mine it in Afghanistan, ship it across Europe, and it was more expensive that gold so it would have its own budget line on a commission." Dragon's Blood "It has a great name, but it's not from dragons. [The bright red pigment] is from the rattan palm." Cochineal "This red dye comes from squashed beetles, and it's used in cosmetics and food." Cadmium Yellow "Cadmium yellow was introduced in the mid 19th century. It's a bright yellow that many impressionists used. Cadmium is a heavy metal, very toxic. In the early 20th century, cadmium red was introduced. You find these pigments used in industrial processes. Up until the 1970s, Lego bricks had cadmium pigment in them." Emerald Green "This is made from copper acetoarsenite. We had a Van Gogh with a bright green background that was identified as emerald green. Pigments used for artists' purposes can find their way into use in other areas as well. Emerald green was used as an insecticide, and you often see it on older wood that would be put into the ground, like railroad ties."


Rodriguez A.,University of the Basque Country | Eremin K.,Straus Center for Conservation | Khandekar N.,Straus Center for Conservation | Stenger J.,Straus Center for Conservation | And 3 more authors.
Journal of Raman Spectroscopy | Year: 2010

Applied tin-relief brocade (commonly called applied brocade) refers to adecorative painting technique using tin leaf applied over a supporting reliefmass (filling) which is glued to the artwork to simulate gold and silver textilebrocades. This originated in Germany ca 1415-1430 and spread across Europe fromthe mid-15th century to the mid-16th century. This study focuses on six early16th century altarpieces in the Basque country in the present province ofGuipúzcoa, Spain. Cross sections of the ground and applied brocade wereinitially examined with optical microscopy and staining tests for proteins andlipids to assess the layering structure and materials present. Furtherexamination with Raman spectroscopy, Fourier transform infrared spectroscopy(FTIR) and scanning electron microscopy with energy dispersive X-rayspectroscopy identified the inorganic and organic components of the variouslayers. Raman spectroscopic mapping was used to image the location of phases inselected cross sections. Five altarpieces from Spain had calcium sulfategrounds, whereas one thought to come from Flanders had a calcium carbonateground. Raman and FTIR spectra showed that the thick, coarse lower ground layer(yeso grueso) is anhydrous calcium sulfate (anhydrite) whereas the fine, thinupper ground layer (yeso fino) is calcium sulfate dihydrate (gypsum). Thefilling masses consisted of different mixtures of inorganic (chiefly gypsum oranhydrite but occasionally with other pigments or additives) and organic(protein and/or oil or beeswax) materials. Comparison of the documentedhistorical techniques with the materials found provides insight into localvariations of the technique. Copyright © 2010 John Wiley & Sons, Ltd. Source


Kennedy A.R.,University of Strathclyde | Stewart H.,University of Strathclyde | Eremin K.,Straus Center for Conservation | Stenger J.,Straus Center for Conservation
Chemistry - A European Journal | Year: 2012

The first systematic series of single-crystal diffraction structures of azo lake pigments is presented (Lithol Red with cations=Mg II, Ca II, Sr II, Ba II, Na I and Cd II) and includes the only known structures of non-Ca examples of these pigments. It is shown that these commercially and culturally important species show structural behaviour that can be predicted from a database of structures of related sulfonated azo dyes, a database that was specifically constructed for this purpose. Examples of the successful structural predictions from the prior understanding of the model compounds are that 1) the Mg salt is a solvent-separated ion pair, whereas the heavier alkaline-earth elements Ca, Sr and Ba form contact ion pairs, namely, low-dimensional coordination complexes; 2) all of the Lithol Red anions exist as the hydrazone tautomer and have planar geometries; and 3) the commonly observed packing mode of alternating inorganic layers and organic bilayers is as expected for an ortho-sulfonated azo species with a planar anion geometry. However, the literature database of dye structures has no predictive use for organic solvate structures, such as that of the observed Na Lithol Red DMF solvate. Interestingly, the Cd salt is isostructural with the Mg salt and not with the Ca salt. It is also observed that linked eight-membered [MOSO] 2 rings are the basic coordination motif for all of the known structures of Ca, Sr and Ba salts of sulfonated azo pigments in which competing carboxylate groups are absent. The fine art of coordination polymers: The first series of structures of an azo lake pigment is presented, namely, Mg, Ca, Sr, Ba, Cd and Na salts of the printers' and artists' material Lithol Red. These structures (see figure) show remarkable similarities to previously studied structures of model dyestuffs and hence the structures of the dyes can be used to predict the likely structure of sulfonated azo pigments. Copyright © 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim. Source

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