Characteristics of loess plaster of Middle Asian mural paintings (8th century, Pendzhikent): exposed porosity, mean diameter of pores, water vapour absorption and bending strength, have been estimated. The evaluation of the changes of these characteristics after treatment with 10% polybutyl methacrylate solutions in xylene and in xylene-ethyl alcohol mixture under equal laboratory conditions has revealed no difference between the two methods of treatment. See also AATA 13-360, and 13-1017.