Page:Cyclopedia of Painting-Armstrong, George D (1908).djvu/427

Rh and umber lose some of their substance in the oil, but to what extent manganese or iron soaps are formed with the oil acids is not known. Both umber and black manganese boiled with oil darken it.

Marbleizing Glass. One method of marbleizing glass consists in applying a mixture of varnish and oil to the surface of water of proper extent, and spraying or blowing upon the layer or film of oil and varnish dry colored powders to represent the mottled, speckled, veined, or other appearance of mottled or other stone. The glass is prepared by being coated upon one surface with varnish or japan, and is then placed upon the powder supported by the oily surfaced water, and the powder immediately adheres or fastens itself to the varnish or japan on the glass. The apparatus for distributing the color consists of a spraying device or distributor having a receptacle for the composition, which is introduced through a hole covered by a perforated cap. There is a diaphragm with holes or perforations, which are closed by a slide. This diaphragm separates the space containing the mixture from a passage or extension, the end of the casing of the passage being contracted sufficiently to fit upon the end of the bellows. To operate this device the receptacle is filled with the composition, the cap is secured in its place, and the slide lifted. The bellows are then operated, and the pressure of air drives the mixture in fine spray or drops upon the surface of the water. The device for applying the dry colors to the floating sheet or drops of oil and varnish is similar to that described, but in order that a number of colors may be sprayed or blown upon the floating oil and varnish at the same time, the receptacle is divided at the end into two or more parts, and a shaft, having agitators, is extended through them. The air is forced by bellows or other suitable means through perforations in the diaphragm. Caps cover the various chambers, etc., and are perforated to permit of the escape of the powder. In operation the air from the bellows or