The fillings vised for stopping the suction of wood, plaster, etc., previous to painting, may vary according to the nature of the work. A very commonly used filler is made from starch by incorporating with it some linseed oil and varnish, adding a drier, and then thinning with petroleum naphtha. The American fillers are made from inorganic materials, such as ground silica, steatite, china clay, or barytes, and these are ground with raw linseed oil, grinding japan, and turpentine or liquid driers. These fillers set extremely hard. They are coloured when necessary with the usual pigments. A very common filler for plastered walls is made by dissolving good jelly size in hot water, and thoroughly mixing with it sufficient whiting to give it body.