Paper degradation may be the result of endogenous factors, which depend on the fibrous composition and the nature of additives, on the technology of paste preparation and paper making, and of exogenous factors, which are detennined by processing conditions (printing, writing, etc.), by paper utilization and storing conditions (humidity, temperature, the presence of some polluting substances within the atmospheric air) (fig. 1 . 1 ). Endogenous and exogenous fac tors may appear simultaneously, may intensify themselves; they affect physical and chemical properties of paper, that change in time.