Graphite paints, red oxide paints, and paints made from basic sulphate of lead are also used for the preservation of ironwork. Bituminous paints are also extensively used for painting Ironwork, such as gas-holders, bridges, docks, etc., on account of their comparative cheapness and anti-corrosive properties. They are composed of an asphalt or bitumen base dissolved in coal tar or naphtha solvent. They are usually black, but other colours can be obtained, which are made by the addition of strong staining pigments to the base.
Anti-fouling Paints.—These paints are used on ships' bot toms in order to prevent the growth of barnacles and weeds.
They are as a general rule quick-drying iron oxide paints, to which a proportion of poisonous material, such as white arsenic, copper suboxide, mercury oxide, etc., has been added. In contact with sea water, these poisonous materials gradually dissolve and thus inhibit any deposit or growth forming on the ship's bottom.
Metallic Paint.—Metallic paints, such as aluminium, copper bronze and gold paints are prepared by mixing the finely powdered metals, or alloys, with suitable varnish media. The metals must be in an exceedingly fine state of sub-division, and are manufac tured from the metal leaf by special processes involving the use of intricate grinding machinery. The media used may be either thin varnishes or pyroxylin solutions.
Fireproof paints are made for use on wood work, composition boards and other inflammable material. They are usually ordinary oil paints containing a proportion of fine as bestos, borax, sodium tungstate, and other fire-retarding materials.
Automotive and Other Industrial Enamels.—A special class of exterior enamel for automotive or other vehicle finishing has been developed on a quick drying basis to replace the older multi coat slow drying systems of a few years back.
The lacquer base (nitro cotton in suitable solvent) enamel in troduced in the early is applied by spraying, dries in a few minutes, can be polished to a high gloss and possesses exterior durability very much superior to the copal varnish and processed oil enamels formerly used.
Synthetic resin enamels, mostly of the alkyd (glycerol phtha late) type, have become increasingly popular for automotive and other industrial finishing, due to superior gloss retention and general economy of application.
Synthetic base enamels of the phenolic, alkyd, and urea resin types have proven very satisfactory in the finishing of house hold appliances. These are force dried at fairly high temperatures, have a beautiful lustre, and are resistant to mechanical and chemi cal (washing powder, ammonia, grease, water, alcohol) abuse such as one might expect to find in the home. See also DISTEMPER; LUMINOUS PAINT.