Auto paint jobs are a meticulous multi-stage process. Whether you're repainting your whole car or just touching up a few scratched or dented panels, here is what's involved.
- The tools. For your car painting project, you would need a paint spray gun, compressor, sandpaper, paint thinner, masking paper, and of course the paint itself. If available, you should also have a dual action sander/buffer (which can be rented). You can choose among a variety of paints, but for most purposes, urethane paint will be the most suitable for your car.
- Clean your car. Before doing any paint job or retouch, be sure to clean your car thoroughly with auto detergent. Rinse the car properly, and follow up with wax and grease removers. Make sure you are working in a dry environment, as moisture build up will ruin a paint job.
- Sanding. With a sander, strip off the coating on all surfaces you will be painting. Use a dual-action air sander, if available. This prevents uneven sanding as it both rotates and oscillates, so you don't have to compensate for possible over-sanding manually. If you will be painting the car with the same color as the original, it would be enough to sand down to the original layer of paint. If you plan to change the color, then you should be able to sand beyond the original layer of paint. You can use duct tape to protect rubber moldings and glass from being scratched by the sander.
- Filling. If your car's body has dings and dents, you should now cover them with plastic filler. These usually come in powder or clay form, and you should mix these according to instructions. Apply with a plastic spreader, and make sure the resulting surface is smooth. Once the filler has dried, you can now shave and scrape it with a sanding board, such that it follows the original contour of the car's body closely. Finish off the smoothing and sanding with the dual-action sander, using a 120 to 150 grit sandpaper. The filler's surface would usually be rough, so you need to apply acrylic glazing for a smoother surface. Once the glazing has dried and hardened, it's time to sand the area again.
Rusted parts will need special attention, as rust is likely to eat into metal, and cause uneven paint finish later on. Rusty parts should be cut out replaced immediately.
- Masking. After filling, the car should be thoroughly cleaned and rinsed anew. Once everything is dry, the next step is to mask parts of the car that will not be painted. This is to protect the paint from reaching glass, rubber moldings and areas you don't intend to paint. You can use weather stripping. If this is not available, then you can simply use thick masking tape and old newspapers. You should also mask the area underneath, forming a curtain, so your paint doesn't reach the under-chassis.
- Spraying the primer. Before you spray paint on your car, give it a thorough wipe down first, just to make sure there are no dust particles or other possible contaminants. Once this is done, you can now spray the affected portion with epoxy primer. Once the primer has dried, it's now time to sand it once more. This is your chance to correct any imperfections or bumps that may have not been noticed earlier. Once sanding is finished, give your car another thorough wipe down. It's now time to apply another coating of primer. This layer should also be sanded with a finer 600-grit sandpaper.
- Re-washing and re-sanding. Before the topcoat is applied, you should remove all masking and wash the car again thoroughly. At this point, you should wet-sand the edges quickly with smooth sandpaper (600 grit).
- Spraying the basecoat and topcoat. The car should be remasked, and then dusted thoroughly, to make sure there are no dust particles present while painting. At this point, the basecoat is sprayed onto the car. The spray gun should be kept perpendicular to the area being sprayed at about ten to twelve inches away, and you should apply paint as lightly as possible, with quick, overlapping strokes. When the basecoat has dried, you can now apply the topcoat, using the same spraying technique. Then when the topcoat has dried, you can apply the clear coat using the same technique. At this point, you would have to wait a day or two to let the paint cure.
- Color sanding and buffing. The last steps here are color-sanding and buffing. When the paint cures, there are minor imperfections and roughness, and this has to be evened out with a smooth 2,000-grit sandpaper. Be sure to clean the car thoroughly before color-sanding. Color-sanding is a wet process, meaning you have to apply water while sanding an area in only one direction (not in a circular motion). Sand the paint until the finish is dull and smooth. Once the painted areas have been color-sanded, the next step is buffing the car. Apply buffing compound, and use a wool buffing pad with the dual-action buffer. Use light pressure only, and set the buffer to the lowest speed. After buffing with wool, replace the pad with a softer foam pad, and buff once more.
Once you've finished buffing, the car should now have a smooth and shiny finish. Don't wax the car until after two months, to let solvents and other particulates escape through the air. Painting a car may be a complicated process, but these steps are all necessary to achieve that smooth, shiny finish.