The conservator must be aware of the historical techniques and materials used by individual artists and how they change with age. Unfinished paintings and diaries and technical notes written by the artists are sources of information about the works of dead artists, dialogues for those of living artists. A 1981 survey indicated that 33 individuals and institutions are compiling technical data on the work of contemporary artists. The Ralph Mayer Center for Artists' Techniques at the University of Delaware will collect information about both historic and contemporary techniques and materials. See also AATA 21-1940 for more information about the database of the center.