Da internet:Echard poco attendibile… In particular, the proteinaceous binding medium and the calcium sulfate components (bassanite and anhydrite) that have been identified in the lower layers of the varnish microsample could be related, to a certain extent, to the ground materials of earlier Italian paintings …Direct analyses were performed on instrument varnishes, without any sampling and non-destructively, showing inorganic elements such as lead, mercury and iron that could be related to siccatives or pigments.