Stone tools in the sun: the effect of UV light on the preservation of flint surfaces and adhesives.

Functional interpretation of prehistoric stone tools is sometimes compromised by post-depositional alterations that may hinder wear and residue observations, which may complicate a reliable reconstruction of past human activities. Indeed, once discarded, stone tools are exposed to a broad range of degrading agents (before and after burial) and these may impact the preservation of use-wear and residues on their surfaces. UV light is one of the first agents potentially altering functional evidence on stone tools. Even though UV light is assumed to potentially affect stone tool surfaces, its effect on use wear and residues has never been systematically tested by archaeologists. In this poster, we present the results of an experiment in which we used a UV chamber to expose experimental tools with and without organic adhesives to UV radiation equivalent to one year of daylight and we discuss the changes observed. The results of the experiment show that flint tools and adhesives are modified due to UV light and that these changes need to be taken into account when examining and interpreting archaeological material with the help of experimental reference collections.