Basic Auto Body Paints
All automotive paints are made up of three different elements. These three elements do different things.
The pigment is a finely-ground powder that gives paint its color. Pigment also has other jobs. In "red-lead" primer, it helps protect against corrosion. The pigment in spray putty helps give you a good depth of substance so that when it dries, you can sand it.
The binder in paints holds the pigment together and enables the pigment to stick to the surface. Binder also helps form a glossy, protective film over the pigment after the paint dries.
Solvent is the liquid in paint that makes the paint runny and enables you to apply it. Solvent evaporates quickly. After it has dried, what is left is the finish on your car, truck, SUV or van. There are various types of solvents and they are matched with the different types of paint. When you thin paint, make sure to use the correct type of solvent.
Not too long ago, there were only two types of auto-body paint: synthetic enamel and nitrocellulose lacquer, commonly called "cellulose." Today, however, manufacturers have gone to a variety of other paints that are better for the mass production of vehicles.
Enamels are often used, of which there are two types. One works by allowing the solvent in the enamel to evaporate, thus forming the finish. The other types works by a reaction between two chemicals: when the two chemicals combine, the reaction allows the enamel to form the finish. Enamels often contain a reducer, which thins the paint to the correct consistency for spraying.
You will find acrylic lacquers in spray paint in a can, but it can also be used with a spray gun. Acrylic lacquers have superior gloss color retention characteristics and dry very fast on the surface. But full drying can take as long as 16 hours. Usually you have to polish this type of paint to achieve the best gloss finish. Remember to use the undercoats and thinners recommended specifically for acrylic lacquers rather than regular cellulose undercoats. It is also important to avoid mixing different brands of acrylic lacquers. Why? Because manufacturers use different formulas for these types of paints. Mixing may cause the paint to crack or graze. Acrylic lacquers are normally quite thin, so you usually have to apply a number of coats to bring the paint up to the proper paint depth. Ordinary acrylic lacquers harden and dry when the solvent in them evaporates. But manufacturers also use "thermoplastic acrylics" (TPA) in their paint processes. TPA softens when heated. Car companies spray paint vehicles with TPA-type lacquer on the production line then bake them. This dries the lacquer but also softens and smoothes the plastic composition. You can use ordinary acrylic lacquers to repair TPA paints in the home workshop or you can use specially-formulated paints. These are known as low-bake enamels, synthetic and oil resin-based paints, lacquer paints, and others.