ABSTRACT
Photographs are found in practically all museums and archives, generally in large numbers. They are cultural heritage, an artistic medium, historical documents and a visual documentation medium of the 20th century. One of the main problems is the gradual degradation caused by the relatively limited stability of the photographic materials. In the case of black and white photographs problems arise of de-silvering, yellowing, acidity and broken glass negatives. In general, after 70 years damage is practically always present. For colour photographs the deterioration process is even more rapid, with colour fading causing visible changes after 30 years. A further problem is the number of photographs. Photography is a ‘mass medium’, which means that picture archives can be very large and picture collections of more than 100,000 pictures are not infrequent.
