and resistance to various environments. It gives the paint its strength and life. The vehicle is usually
divided into two parts; they are volatiles and nonvolatiles.
a. Volatiles. Volatiles are the nonsolid portions of vehicles that evaporate. They consist of
thinners and solvents. Volatiles, more commonly called thinners, are organic liquids that are used to
reduce the viscosity (thickness) of a vehicle or paint to a suitable brushing or spraying consistency.
Volatiles are also used to control many other properties of paint, such as the ability to penetrate and/or
wet the surface being coated, the leveling, the lap time (period between paint coats), the dispersion of
pigments, and the ease of brushing or spraying. Some of the more common volatiles are turpentine,
mineral spirits, naphtha, xylene, acetone, and various alcohols, ethers, ketones, and esters. Water, of
course, is used as a thinner for water-based paints. When selecting volatiles to thin paint for use in the
field, you should follow the directions of the paint manufacturer or the specifications, since some paint
vehicles will not mix with certain volatiles.
b. Nonvolatiles. Nonvolatiles are the solid, nonevaporating portions of a paint that are left after
the solvent evaporates. They are the solid portions of the vehicle that form the actual film on the
surface. They consists of film-forming materials, such as drying oils, driers, resins, and varnishes.
(1) Drying Oils. Drying oils are nonvolatile vehicles. A nonvolatile vehicle is defined as the
liquid portion of a paint aside from its volatile thinner and water (or other solvent). Not all oils are
drying oils. An oil is classified as a drying oil if it will set or harden under normal exposure conditions
when applied as a thin film. Some of the most commonly used drying oils are linseed, soybean, tung,
oiticica, perilla, fish, and dehydrated castor.
(a) Linseed oil. Linseed oil, the most important of drying oils and the principal
nonvolatile paint vehicle, is obtained from flaxseed. It is used as the basic vehicle in paint because it has
a natural ability to dry in the open air, forming an elastic, durable, solid film which resists the attack of
weather and wear. The addition of a drier will hasten its normally slow hardening rate.
(b) Soybean oil. Soybean oil, a slower drying oil than linseed oil, is generally used with
faster drying oils. The main use for it is in varnish vehicles for interior paints and enamels. Paints made
with soybean oil resist yellowing. It is used in some of the best interior, white enamels.
(c) Tung oil. This oil is one of the chief oils used in the manufacture of fast-drying,
waterproof, oil varnish. Since raw tung oil dries rapidly but not to a smooth film, it is not used in
exterior house paint; whereas linseed oil is almost universally used. Its chief usage is in the manufacture
(d) Oiticica oil. This oil is extracted from the seeds of certain trees growing in northern
Brazil. It is similar to tung oil and is used in the manufacture of paint and varnish.