ABSTRACT
From a careful look at unprotected stained-glass windows, it may be seen that their aspect is deteriorated for the colour, the grisaille and their transparency due to a deposit on the two faces, outside and inside. A straightforward characteristic is the black colour of the deposit which suggests that responsible agents and mechanisms are likely to be primarily the same as those acting for the soiling of other opaque materials. Indeed, it is at present well known that patinas and crusts may develop at the surface of inert or reactive substrate, due to the deposition of atmospheric particles and additionally due to interaction with the material matrix (Camuffo et al. 1982, Lanting 1986, Haynie & Lemmons 1990, Hamilton & Mansfield 1993, Sabbioni 1995, Pio et al. 1998, Pesava et al. 1999, Ausset et al. 1999, Lefèvre & Ausset 2002, Watts & Hamilton 2003). Chemical and microscopic analyses show that they are primarily formed of gypsum and carbonaceous material comprising soot and micro-soot particles, which interestingly are important components of airborne particles but not in the same proportions.
