Various methods of bleaching in common use have been studied. Three types of aged paper (rag, chemical and mechanical woodpulp) were washed, deacidified, bleaches, deacidified again and artificially aged. The physio-chemical effects of bleaching were measured by the degree of overbleaching, yellowing and loss of mechanical resistance as well as by analysis by electron microprobe and gel permeation chromatography. Seven methods were finally retained and their application is described in detail.