Whiting has been classed as an adulterant in paint, but this applies only where it is used in replacing a higher priced material without any tangible reason. As we shall see in the case of putty, there is no pigment that will take its place, and in any number of special paints its presence is quite necessary. So, for instance, in some dipping paints that are sold in paste form to implement makers and others, where it would be a waste of money to use high priced colors without any extender or filling material. Most of the other extenders are too apt to settle and cake hard in the tanks, because of the volatile thinners used to bring the paints to the right consistency for dipping, while those of very low specific gravity are not well adapted to the purpose. In certain kinds of machinery paints, such as fillers, where the material is applied with the spatula or knifed in, a certain portion of whiting is beneficial. In fact, wherever paint is not exposed to sulphur gases a reasonable percentage of whiting is in place. In nearly every specification for paints issued by railroads, excepting in whites, an amount of not less than 2 or 3 and not over 5 per cent of carbonate of lime (whiting) is called for, and government specifications permit the presence of whiting or carbonate of lime in all oxide of iron or earth paints to that extent. A certain percentage of whiting with red lead in oil prevents it from sagging or running, and grainers add whiting to their color in oil to keep it from flowing together after wiping out or combing.
Whiting does not work well when added to a pigment in oil that is to be thinned with varnish. It is very apt to show up granular. Whiting when thoroughly dry will average from 8 to 9 pounds per gallon in weight, according to fineness. Taking American Paris white as a basis, a paste of whiting and oil will consist of 82 pounds pigment and 18 pounds oil, weighing when ground about 16 pounds per gallon. In semi-paste form 75 pounds pigment and 25 pounds oil a gallon after grinding will weigh about 13 pounds. In liquid form 60 pounds dry whiting ground with 40 pounds of oil will weigh 11 pounds per gallon. Whiting mixes well with an emulsion of oil and water in a paint made from lead carbonate, but does not wear well if used for priming wood, because the water of the emulsion is absorbed by the wood, and there is not sufficient binder left in the paint, causing it to peel or scale.