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In this review, a brief description of how animal skins were transformed in leathers in Europe using different vegetable tannins will be presented. Special attention will be dedicated to the description of the type of tannins and the characteristics of the most important type of historic leathers thus obtained. The text will also focus on the description of the techniques used in the identification of these tannins in historic objects: colorimetric tests and spectroscopic analysis.

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Characterisation of 17th-18th centuries damask and gilt leathers by ATR-FTIR ResumoNeste artigo apresenta-se o estudo químico dos taninos usados na curtimenta vegetal de duas tipologias de cabedais históricos e decorativos europeus pertencentes a acervos de colecções portuguesas, os cabedais adamascados e os guadamecis, datados dos séculos XVII e XVIII. Foram analisados extractos preparados a partir de fibras recolhidas nesses cabedais através da técnica de espectroscopia de infravermelho com transformada de Fourier (FTIR) em modo de reflectância total atenuada (ATR). Os resultados obtidos foram comparados com os dados de diversas amostras de referência de taninos que, de acordo com fontes documentais, se encontravam, na generalidade, em uso na Europa na Idade Moderna. Este estudo permitiu caracterizar, na maioria dos casos, os taninos utilizados na produção dos cabedais estudados e, paralelamente, detectar uma alteração química dos cabedais, neste caso a hidrólise do colagénio, a qual não era perceptível visualmente. Palavras-chave Cabedais decorativos Curtimenta vegetal Taninos ATR-FTIR Deterioração AbstractIn this paper it is presented the characterisation of tannins used in the vegetable tanning of two types of European historic and decorative leathers from Portuguese collections, damask leathers and gilt leathers, dated from the 17th and 18th centuries. Extracts prepared from collected leather fibres were analysed by attenuated total reflectance -Fourier transform infrared (ATR-FTIR) spectroscopy. Results were compared with data collected from different reference vegetable tanning materials which, according to historic and technical literature, were used in Europe during the Modern Age. This study allowed, in most cases, the characterisation of the tannins used to produce the studied decorative vegetable tanned leathers and, at the same time, the detection of chemical deterioration of leathers, particularly collagen hydrolysis, which was not visually perceived.