Abstract
Man has always been confronted with the alteration and degradation of cultural assets, whether natural, i.e. caused by their environment over time, or the product of human action. Having recognized early on the need to protect the stone surfaces of monuments, sculptures or wall paintings, he set about designing and applying various products to try and preserve them better. But because of the complexity of the surface transformations affecting this type of heritage object, and in order to obtain conservation results that were not random, it proved necessary to develop a scientific approach to conservation. For more than a hundred years, a science of heritage materials has been gradually developing, in which chemical analysis in its various aspects has, over the last forty years, gradually taken on an important role. The variety of spectroscopic techniques has revolutionized the science of conservation, enabling both an analytical approach on site, and an increasingly fine and precise analysis of the constituents of the layers of a mural painting in the laboratory.
The understanding of surface transformations in stone and mural paintings is based on crystallochemical and geochemical approaches, as well as on organic chemistry studies and analyses. By way of example, we'll look at how analyses carried out at micrometric to nanometric scales have made it possible to understand the degradation mechanisms of pigments such as minium, or the role of expansive clay minerals in certain stone degradations. Another example is the use of stable isotope geochemistry to trace hygroscopic salts as degradation agents on stone surfaces.
