How To Paint A Car
After the bodywork is done, painting is the last major step in old car restoration. Should you paint your car yourself?
Many steps are required before the painting actually begins. These include surface preparation, proper sanding techniques, using the correct products, primer, block sanding, more primer and more sanding. If you skip over any of these steps, the paint will not adhere properly, you'll see defects in the finish, and you've wasted your time, money, and energy. On the other hand, you'll be spending $3,000-$5,000 or more to have someone else paint your car. Consider investing $500-$800 in paint equipment (that you will probably use again) and paint your car yourself.
Preparation, Preparation, Preparation
The key to any successful paint job is in the preparation. Before you begin painting your car, you need to have a plan. First of all, where will you be doing the work? It may be illegal to paint your car where you live.
Before you start, check local environmental regulations. The local fire department or auto-body supply store are good places to ask. An alternative would be finding a spray booth to rent. If neither of these are possible, you can still prepare your car for a body shop. It's a good way to save money.
Are you planning to strip the car down to bare metal, or paint over the existing finish? There's several methods of paint removal, but if you're on a tight budget, paint stripping by hand is possible using several sanding techniques and chemical paint strippers.
Stripping your car down to bare metal (or fiberglass) ensures there's no hidden damage, but also adds the additional work of reinstalling everything, gapping the panels, replacing seals on door handles, etc.
Mask up areas you don't want paint on. Use masking tape and paper or plastic sheeting. Take your time with this step, it will help avoid unwanted overspray. If you applied any bondo or filler, a good sealer should be used before spraying the primer. Some putties will absorb the primer and reducers and give you a variety of problems.
Apply a self-etching primer over any bare metal. Etching primers are lacquer-based and formulated with a very small amount of acid, which "etches" into untreated bare metal. It offers corrosion protection and a strong lasting bond to the metal. This makes it ideal for patch repairs such as floors and fender patches. Self-etching primers are compatible with most primers, including urethanes. They are also compatible with most urethane, acrylics, enamels. They are not compatible with epoxies.
Prime the Panels
Many two-part urethane primers are high-build and will hold up better than one-part primers or lacquer primers. You may want to spray as many as four or five coats. Allow the primer to air dry for at least one full day.
Block-Sand the Panels
Block-sanding removes any waves and gets the panels as straight as possible. Start with 120 or 180-grit sandpaper on the block, then 240-grit and finally 320-grit. Spray guide coats in contrasting colors between each sanding step. Re-prime any areas that show body filler. Final sand with 400-grit on a dual action sander. This will remove any marks left by the block sanding.
Before spraying the final coats, clean the sanding residue off with soap and water. Use a high-pressure blow gun to get all panels clean and dry. Clean the car with solvents to remove any contaminates on the panels that may cause paint to properly adhere. This reduces the risk of getting "fish eyes" in the paint. Final step before spraying is to use a high-quality tack rag to remove any dust that has settled.
A spray gun, air hose, an air compressor, and moisture separator are the minimum requirements for painting your own car. A paint gun has a much higher duty cycle than an impact wrench or an air ratchet, so the amount of air used is much higher. This means the compressor will be running longer, building more heat, and developing more condensation in the line.
read Selecting a Garage Air Compressor
Nothing ruins a great spray pattern as much as water droplets. A good water trap is very important. There should be a trap on the compressor, but there should also be a trap on the gun itself. This allows condensation in the air line to be kept out of the paint gun.
Water-based automotive paints require specialty guns which have stainless steel and plastic internal parts, making them corrosion resistant. A conventional spray gun used with water-based paint will work, but if not cleaned thoroughly will corrode internally.
There are two common filter types that attach to the paint gun. The less expensive is the ball-style, which works great. The more expensive is a desiccant style, which has the added advantage of allowing the painter to see when it is about to fill with moisture. Both of these attach to the paint gun right where the air hose enters.
How Much Paint Will I Need?
Depending on the size of your car, you'll probably need a gallon of primer, two or three gallons of topcoat, and two gallons of clear coat. It's a good idea to factor in some practice beforehand, and for corrections needed afterward.
Safety hazards when painting your car are very real. Disposable nitrile gloves, a head sock and full body covering are recommended, and a good respirator is essential. Remember to change the respirator filters often. Always wear eye protection.
Be realistic with your expectations of your first automotive paint job. You may get runs, sags, dirt, or dry spots. Fortunately, most of those problems can be corrected with color sanding and buffing.
How long should painting your car take? I completed my 1970 Chevelle in about a month from the time the bodywork was done until it was painted and ready to drive out of the garage (I waited another week before starting to wet sand the clear coat).
Spray Painting Your Car
Hold the spray gun about 6-inches from the panel and spray in a side-to-side sweeping motion. Spray about 50 percent overlap from the last line of paint that you laid down. Several light coats are best, followed by one slightly heavier coat.
After the car is painted, remove the masking tape and paper carefully. Allow the paint to air dry for at least one full day. Before wet-sanding, any dirt nibs can be removed with a dirt nib file.
Wet-sanding paint is a messy but necessary step to remove any orange peel in the paint. You will need a wet-sanding bucket and three or four 6-inch blocks each with different hardness. The harder blocks are best for taking out orange peel. For highly curved areas the softer blocks are better.
Start with a 1,000-grit sandpaper. The best way to sand is by hand, but it also can be completed with a dual action sander. After wet-sanding with 1,000-grit sandpaper, wash the car and switch to 1,500-grit and then 2,000-grit. Be careful around the edges not to cut through the clear, or you will have to repaint.
After wet-sanding, buff paint in circular motions with a buffer, being careful not to burn the paint by holding the buffer in one spot for too long. Work with approximately two square feet at a time with each of these steps until the haziness is gone. Use 3M extra-cut or other compound with a wool pad, followed by a rubbing compound, finishing with a swirl mark remover compound.
The chemicals in today's paints are dangerous and can be absorbed through your skin and eyes. The EPA states that the health risks of VOCs include: Eye, nose, and throat irritation; headaches, loss of coordination, nausea, damage to liver, kidney, and central nervous system. When working with these chemicals, you must follow all precautions and make sure you use all of the required safety equipment.