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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.

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.

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.

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