Types of Body Paints Used for Refinishing
For the home mechanic, using original manufacturers' paints for refinishing is usually not a good idea. Why? Because after applying these paints (called TPA-type paints) you have to bake your vehicle at a high temperature. Doing so requires special equipment and would melt many of your vehicles' plastic parts, including the trim, wires and seats.
TPA stands for "thermoplastic acrylic." When it is heated, this type of paint softens and becomes smooth. Because heating to a high temperature is not practical for the home mechanic, companies have formulated special paints for refinishing. These are known as lacquer paints, low-bake enamels, synthetic and oil resin-based paints, two-pack, and metallic paints.
Dust is one of the biggest problems for the do-it-yourself painter. Therefore lacquer paints (sometimes called "cellulose" paints) are a good choice because they dry quickly. The sooner the paint dries, the less dust can fall on it. Lacquer-type paints require polishing after painting to bring out a high-gloss shine. This type of paint is durable, is relatively inexpensive, and has fewer health concerns than some other types of paint. The main problem with a lacquer-type paint is that it may not be compatible with the paint already on the vehicle. If not, it is possible to apply an "isolator." This forms a barrier between the two kinds of paint. For the home mechanic lacquers work well, although a number of coats are required for a sufficient paint depth.
Enamel paints are inexpensive, are durable and are preferred by those who work on commercial vehicles. Another advantage is that enamels do not react with other paints that lie beneath them. But this type of paint also takes a long time to dry, which makes it susceptible to picking up dust (the longer it takes to dry, the more dust it can pick up): enamel can take up to a couple of weeks to dry completely. Also, nearly all other paints react by wrinkling and crazing if sprayed on top of enamel and enamels cannot be polished once laid down, although it is fairly easy to get a good shine right out of the spray gun. Good paint for "last" paint jobs on older trucks, cars, vans or SUVs.
Two-pack paints are those that dry not by evaporation but by the reaction of two chemicals. They provide a great shine right from the spray gun, the pigments seem to fade less especially with yellows and reds, and they provide a hard, durable finish. The big disadvantage is that they can be toxic, if not lethal, if the user fails to ventilate properly: the result can be spasms and death. For the do-it-yourselfer, these paints are not practical, although about 50% of all refinishers use this in the commercial realm. Caution: be sure to use proper ventilation and proper lung protection when working with two-pack paints.
Low-bake paints require a spray booth or oven with a minimum temperature of 175 degrees F (or 80 degrees C) for drying and setting. This large investment, however, yields superior results.
Metallic paints achieve their effects of reflecting light and unusual shading by employing tiny chips of aluminum in the paint itself. The result in the well-known metallic effect. Any of the above paint types can be made with aluminum chips.
Another technique that is growing in popularity with manufacturers is clear coating over a color base. The base coat is applied as a matte undercoat, followed by one or more coats of clear lacquer.