Matte, porous paint, highly friable and difficult to consolidate without darkening and discoloring, is found in a wide range of objects. Some physical and optical properties of this type of paint, as a result of high pigment volume concentration and diffuse surface reflectance, are presented with a stress on ramifications for treatment parameters. The problems encountered in transferring the results of controlled laboratory studies into effective conservation treatment procedures are also discussed in reference to painted ethnographic wood objects and contemporary works of art on paper (with a cautionary note on undesirable solvent sensitivity).