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• ATR-FTIR spectroscopy is used to assess the condition of historical silk samples. • Evaluating the conditions of historical textiles guides conservation and preventive measures. • Differentiation between original and later interventions is also possible. • Visual, bivariate and multivariate methods are used to evaluate the data. • Spectral evaluation reveals deterioration markers, explained according to literature. Understanding the conservation condition of historical silk yarn allows to define appropriate storage, care and display of historical silk collections. This paper discusses the characterisation of silk fabrics from a collection of traditional Japanese samurai armours which date back from the 16th to the 20th century (Morigi Collection, Museo delle Culture, Lugano, Switzerland). An analytical protocol to assess silk fabrics conditions was defined, based on microinvasive ATR-FTIR spectroscopy. In particular, the amide I and II region was studied in order to extrapolate the conformational information about silk proteins. According to literature, this kind of information can be related to different degradation stages. A linear correlation was found between the amide I and the amide II shifts, allowing to assess the silk fibre condition. Along with this bivariate approach based on intensity ratios, a multivariate approach based on Principal Component Analysis was also applied to ATR-FTIR spectra. This allowed to group together silks with the same state of preservation. The findings of this research offer a valuable method to researchers and conservators to identify the most damaged textiles; the differentiation between original and restoration materials was also possible in some cases. [ABSTRACT FROM AUTHOR]

To correctly manage a collection of historical silks, it is important to detect if the yarn has been originally subjected to degumming. This process is generally applied to eliminate sericin; the obtained fiber is named soft silk, in contrast with hard silk which is unprocessed. The distinction between hard and soft silk gives both historical information and useful indications for informed conservation. With this aim, 32 samples of silk textiles from traditional Japanese samurai armors (15th–20th century) were characterized in a non-invasive way. ATR-FTIR spectroscopy has been previously used to detect hard silk, but data interpretation is challenging. To overcome this difficulty, an innovative analytical protocol based on external reflection FTIR (ER-FTIR) spectroscopy was employed, coupled with spectral deconvolution and multivariate data analysis. The ER-FTIR technique is rapid, portable, and widely employed in the cultural heritage field, but rarely applied to the study of textiles. The ER-FTIR band assignment for silk was discussed for the first time. Then, the evaluation of the OH stretching signals allowed for a reliable distinction between hard and soft silk. Such an innovative point of view, which exploits a "weakness" of FTIR spectroscopy—the strong absorption from water molecules—to indirectly obtain the results, can have industrial applications too. [ABSTRACT FROM AUTHOR]