Analysis of a questioned document printed by a silver-based process

Abstract The document in question was a reproduction of a 1923 document. The reproduction was allegedly made in 1946, but it was suspected to have been made at a later date by a photocopying method. A chemical analysis showed that the reproduction was not made by a carbon-based process, but by a silver-based process, such as that used to make photo-static copies. Thus the possibility that it was produced in 1946 could not be excluded. The chemistry behind the method used to distinguish the two types of reproductions is described.