EN
Specific damage of paper, whose causes have not been sufficiently explained, include foxing and downy destruction. Foxing is a term which describes small rust coloured spots which frequently appear in books, graphic works and drawings, particularly those from the nineteenth and the first half of the twentieth century. Professional literature offers two theories about the origin of the spots . The iron theory points to the increased concentration of iron ions in paper. The study presents the newest outcome of research conducted by Hideo Arai and Alicja Strzelczyk which support the microbiological origin of foxing and which assume that it is produced by the Aspergillus mould fungi or the Streptomyces bacteria. Downy destruction is an extremely rarely described damage which affects the book as a whole. It causes the loosening and lighter colour of the paper as a result of which the book increases its thickness by 10-14 per cent. This phenomenon is probably caused by household fungi which previously attacked wooden elements. The article describes an attempt at producing the symptoms of downy destruction in laboratory conditions.