[Watermarks of ancient drawings and betaradiographic findings]

Betaradiography, an identification process which satisfies the current requirements for the study of watermarks was systematically investigated in the Graphic Arts Department of the Louvre museum. The curves obtained in this context allowing the evaluation of the weight of sheets using the C-14 plate used for betaradiography and those allowing evaluation of the exposure time as a function of the weight and the choice of films were found to be essential tools for the rational use of this method. Lastly, a filming apparatus adapted to drawings has been developed allowing the first perfectly conclusive betagraphic films in the Drawing Collection.