Textile ageing due to atmospheric gases and particles in indoor cultural heritage.

Textile fibre degradation can be due to many factors. The most common cause is light exposure, but upon the lifespan of a textile, many other environmental factors are to be taken into account. This study focuses on the role of atmospheric compounds-both particulate and gaseous species-on natural textiles ageing, more specifically cotton, silk and wool. To achieve this, reference samples of textiles were exposed to contrasted environments (marine, urban and semi-rural museums and historical buildings) for natural ageing. These conditions were also reproduced in an experimental chamber dedicated to the study of the impact of airborne pollutants on heritage materials. Experimental ageing allowed to highlight degradation mechanisms for each fibre: SO and HCOOH cause the cleavage of cotton's glyosidic links and silk's peptide bonds, while NO promotes the oxidation of the fibres. The most harmful pollutant towards cotton is NO since it causes both its oxidation and hydrolysis. The case of wool is more complicated: HCOOH provokes peptide link cleavage (similarly to silk) but this fibre is less sensitive to SO attacks than silk and even seems to be protected against future alterations after having been firstly exposed to this pollutant. In any case, this experimental study evidences that damages caused by gaseous pollutants are fostered by the presence of particles, regardless of the chemical composition of the particle coating.