(2) Chemical colors. Chemical colors are very important today and are used more than earth
colors because they can be produced cheaper by chemical reaction than from basic raw materials. These
colors consist of blue, green, maroon, orange, red, yellow, brown, and violet pigments.
c. Metallic Pigments. Metallic pigments are used to form a metallic film (barrier) in paint. The
most common are aluminum, copper brown, and zinc:
(1) Aluminum pigments. These pigments are largely pure metallic aluminum and contain
appreciable amounts of a polishing lubricant and a mixture of stearic and other fatty acids. They are
purchased in either paste or powder form. An average formula mix for the production of aluminum
paint is 2 pounds of aluminum powder or paste to 1 gallon of mixing varnish.
(2) Copper pigments. Copper brown powders are usually alloys of copper with small
amounts of zinc and iron. Approximately 1 to 2 pounds of metal per gallon will give good hiding
qualities. Copper brown in combination with small amounts of a toxic substance, such as a mercury or
arsenic compound, is used for making antifouling ship-bottom paint. Various shades, from a light brass
to a dark, antique copper, are used in nitrocellulose lacquer to make the popular brass and bronze
(3) Zinc pigments. Zinc dust is a metallic-gray powder with about 3 percent zinc oxide on
the surface. It has gained importance as a pigment for making metal-protective coatings.
d. Black Pigments. One of the most important black pigments known to the paint industry is
lampblack. It is most commonly used for shading paints, since it has exceptionally great shading
strength and is extremely permanent.
e. Extender Pigments. Extender pigments are certain white or colorless natural substances that
are ground into a fine powder and added to paint. They are used to-
Provide a solid base for color pigments.
Make the paint film porous so that a normal amount of moisture may pass through it
without pushing off the paint film.
Reduce the excessive spreading rate of paint, thereby increasing the thickness of a paint
film.
Some of the more important extender pigments are barytes (barium sulfate), china clay (aluminum
silicate), mica, silica (glass sand), talc (magnesium silicate), and whiting (calcium carbonate).
2-6. Vehicles. In a layman's language, the vehicle is defined as the liquid portion of a paint, enamel,
lacquer, or similar substance which holds the pigment in the solution. The vehicle may be any of such
liquids as volatiles (thinners or solvents) and such solids as nonvolitiles (drying oils, driers, resins, and
varnishes). It is perhaps the most important part of the coating, as it furnishes the desired qualities of
adhesion, toughness, flexibility,
EN0562
2-6
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