N-substituted p-phenylenediamines undergo oxidative deamination both under acid and alkaline conditions. Therefore, before starting a developing process the color developing substance may be converted partially to p-aminophenol and during development p-quinonemonoimine can be formed. These deamination products cause a loss in dye density and cause the formation of undesired indophenol dyes. Redox reactions may produce further compounds which later influence the stability of the image. Direct deamination of the dyes is also possible at low pH, because the dyes can act as N-substituted p-quinonediimines or N-substituted p-quinonemonoimines. The activation energy of this acid deamination is low. Therefore, another fading reaction with high activation energy may determine the dye stability at high temperature and an extrapolation of measurements obtained at high temperature to room temperature then gives the wrong results. -- AATA