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Silk artifacts constitute an invaluable heritage, and to preserve such patrimony it is necessary to correlate the degradation of silk fibroin with the presence of dyes, pollutants, manufacturing techniques, etc. Fourier Transform Infrared Spectroscopy with a Focal plane array detector (FPA FTIR) provides structural information at the micron scale. We characterized the distribution of secondary structures in silk fibers for a large set of South American historical textiles, coupling FTIR with multivariate statistical analysis to correlate the protein structure with the age of the samples and the presence of dyes. We found that the pressure applied during attenuated total reflectance (ATR) measurements might induce structural changes in the fibers, producing similar spectra for pristine and aged samples. Reflectance spectra were thus used for the rigorous characterization of secondary structures. Some correlation was highlighted between the age of the samples (spanning over five centuries) and specific changes in their secondary structure. A correlation was found between the color of the samples and structural alterations, in agreement with the chemical nature of the dyes. Overall, we demonstrated the efficacy of reflectance FPA µ-FTIR, combined with multivariate analysis, for the rigorous and non-invasive description of protein secondary structures on large sets of samples.

Confocal micro‐Raman spectroscopy has been used for the first time in Colombia to obtain the color palette of two Colombian artists from the 19th century: Jose Maria Espinosa and Epifanio Garay. A new technique to handle and store micro‐samples from oil‐on‐canvas paintings is shown, as well as a technique that allows for direct measurement of the front and back surfaces, and stratigraphic layers of the samples, avoiding the classical embedded resin process, thereby increasing the total area of analysis while decreasing the sample size and preparation time before analysis. Additionally, an optical probe for in situ (on‐site) Raman measurements was developed to non‐destructively analyze large paintings. Raman spectroscopic and additional optical microscopic observation resulted in the accurate identification of the artistic technique and the pictorial palette of both artists by using the proposed techniques. Common pigments, such as vermillion, carbon black, Prussian blue, lead white, as well non‐common pigment as siderite (used as yellow by Espinosa), were clearly identified. These palettes, so far only ascribed to these two artists, were the basis for the authentication of two oil paintings. Copyright © 2016 John Wiley & Sons, Ltd.