I was painting a wooden basket yesterday with boilt linseed oil and thus came the inspiration for tonight’s topic. Drying oils are very important in the coatings industry, not as much as in the past but still important.
Back in the day before high quality water based paints had been developed, oil based paints were just about the only good choice except for some specialized applications. Before we go into detail, we should define some key terms regarding to paint.
The vehicle is the part of the paint that forms a tough, adherent film. In oil based paints the vehicle is generally linseed oil. In latex paints the vehicle is some type of synthetic resin.
The second component (not always in paint, but usually) is the solvent, also called the diluent. In oil paint the solvent is now usually petroleum distillates, but before oil was discovered the solvent was almost always turpentine. In latex paints the solvent is water.
The pigment is composed of inorganic powders, usually white or colorless. The pigment can add to the toughness of the film. For commercial house paints the pigment does not provide color (except for white) and usually organic dyes are added to the pigment for colors, although some other materials are also used. For art paints, many times the pigment is also the color in many cases. Pigments are similar for oil and water based paints.
There are also additives in small quantities in most paints to modify drying rate, viscosity, surface tension, and other properties. Water based paint often contains ethylene glycol as an antifreeze.