[Studies on microbiological factor in colour change of mogao graffito's mural. II. Effect of microorganism on the pigment of imitative mural].

Throung the assay and analysis of the imitative mural after cultivated with microorganisms, it has been shown that microorganisms had a pronounced effect on the pigments of the mural: the pigments secreted by microorganisms changed the colour of the mural, and produced much oxalic acid salt, which damaged the formation of crystals of the pigment, moreover, the chemical combination valence of Pb3O4 had been changed due to the metabolic products of microorganisms, that may play an important role in the chemical change of Pb3O4.