There are two general kinds of paint which the home mechanic will most often use. One is oil paint, composed of a pigment such as white lead, with linseed oil used as the vehicle. The other is water paint, in which a whiting and glue are mixed with a water vehicle. There are many classifications of each kind, but we shall list only a few of the more familiar ones.
Exterior, or house paint, as it is often called, is made for all surfaces exposed to the weather and to extreme changes in temperature. It can be applied to wood or metal-provided that the metal has been properly treated before the paint is applied. A good quality exterior paint is tough, water resistant, and dries with a gloss. Any wood surface that is exposed to the weather should receive three coats of exterior paint for maximum protection.
Interior oil paint is similar to that used for outside work, except that it is not as resistant to moisture and temperature changes. It should, however, be sufficiently tough and durable to withstand washings and to keep moisture from penetrating to the woodwork. A considerable amount of moisture will collect around window sashes during the winter, and if the finish on the wood is not of a good quality, water will damage the wood.
Paints for use on floors must be especially tough and elastic. An ordinary outside paint should not be used as a finish for the floor because it will not long withstand the scraping and grinding of footsteps and furniture moved about the floor.
Varnish resembles oil paint in many ways, but it has no colour pigment and, consequently, produces a more or less transparent film when dry. Another characteristic of varnish is that it will "flow out" after it has been applied, and the brush marks will disappear. Varnish is made of linseed oil and a fossil gum. It is ideal for furniture, floors, and for exterior and interior woodwork. There are many different kinds of varnish, developed for specific jobs, but only a few of the more important ones will be covered in this section.
Spar varnish is used for exterior work. It is very tough, resists weather, and dries rather quickly. It is very elastic and can withstand temperature changes well. The name derives from the fact that it was, and still is, used for protecting spars of ships. Spar varnish can be used for interior woodwork but is not very satisfactory on floors.
Floor varnish has the quick-drying characteristics
of spar varnish, combined with the toughness and elasticity required for
endurance and for protecting the wood flooring. This elasticity of floor
varnish prevents it from being scratched easily by shoes or furniture.
Furniture varnish includes many kinds used by cabinetmakers. Some of these will produce a high-gloss finish without rubbing.
Enamel resembles varnish except that a pigment is added to give colouring. Enamel must be applied with the same care that is used for varnish. Enamels come in either dull or glossy finish and can be used for both interior and exterior work, and for furniture. It has the advantage of drying without brush marks.
Enamel under coater is used as the base paint for enamel. This under coater penetrates into the wood pores and provides a smooth surface for the enamel. A flat wall paint can be used for this purpose, too.
Lacquer is a very quick-drying finish, usually made from nitrocellulose. Lacquer should not be applied over oil paints and varnishes because it acts as a remover and softens the undercoat. Lacquer is an excellent finish for metal work, such as brass, that will tarnish if left exposed. There are some kinds of lacquer that can be put on with a brush, but the others should be applied with a spray gun because they dry so quickly.
Shellac is made by dissolving a gum obtained from insects in denatured alcohol. The common mixture is four pounds of shellac to one gallon of denatured alcohol. This is called a "four pound cut" and is generally too heavy for most jobs. It can be thinned by adding more denatured alcohol. Shellac is a quick-drying finish but it is brittle and does not wear particularly well. Moisture will turn shellac white. Shellac can be bought in either white or orange.
Calcimine is a type of water paint. It is composed of whiting, glue, and colouring. The water is added by the painter. Calcimine is used extensively for interior walls and ceilings. It is considerably cheaper than oil paints and has the added advantage of being quickly applied and of drying in a very short time. Another advantage is that calcimine does not have the unpleasant odour of oil paints. A good grade of calcimine does not rub off after it is dry, but it will not withstand water and should not be used in bathrooms and kitchens, where there is a considerable amount of moisture present. Calcimine cannot be washed, and when a new coat is to be applied, the old coating should be removed. This finish can be had in many attractive colours.
There are many different kinds of cold water paints besides calcimine. Some of these are very like calcimine, while others are almost the same as oil paints and can be washed and over painted. Casein and resin emulsion paints are two examples of this type of finish. As each brand differs somewhat from the others, the painter should read the directions on the package carefully and be sure that he fully understands the limitations of a particular paint before he applies it. These paints can be put on with brush, spray gun, or with a roller.
This paint is used to give a rough or textured effect to wall surfaces, or as a finish for plaster walls in such poor condition that a regular oil paint would not prove satisfactory. Plastic paint is stiffened by the addition of whiting, plaster of Paris, or some other material, so that it has sufficient body to prevent flowing once it has been applied.
The composition and, therefore, the characteristics of plastic paints differ according to the brand. For example, some are made with a white lead and oil base, while others are in a powder form and thinned with water before use. In general, the water-thinned paints have more body than the white lead type and produce a roughter texture. Several brands of plastic paint have colouring added, while others can be coloured during mixing or painted over when they are dry.
Surface preparation is important when working with plastic paints, and the manufacturer's directions should be followed carefully. The better brands will list the necessary preparations for different wall surfaces, such as plaster, concrete, wood, and wallboard.
When a textured effect is desired, apply the paint with a brush to a small area at a time ; and then, before the paint has set, texture it, either by using a stiff brush, special tools designed for this work, or even the fingers. Often, the texture produced by applying the paint with a stiff brush is sufficient.