Painting a car used to be relatively simple. There were basically two systems: Lacquer (nitrocellulose and acrylic) and Enamel (alkyd and acrylic). Nitrocellulose lacquer was introduced in 1924 and continued in use until the mid-1950's, when acrylic lacquer replaced it and was used by automakers until the early 1970's. Alkyd enamel was introduced in 1929 and acrylic enamel replaced it in the early 1960's. Each system had its pros and cons, but looked good, and was fairly simple to apply.
The purpose of this article is to present two paint systems that can replicate an OEM look for cars 1972 and before, and can be accomplished by the home restorer. First, let's consider lacquer; both nitro and acrylic. The pros are: they're both easy to apply; can be painted with a syphon-feed gun with a 2-3 horse power compressor; they're easy to blend when touching up; and can be painted in a home shop. On the down side: they're not legal in some states; 80-90% goes up into the atmosphere; the paint is fragile and can develop hairline cracks with age; and it's not readily available, generally being found only on the internet or from an antique auto parts supplier.
Enamels (alkyd and acrylic) have the following pros: alkyd goes on thick and glossy, and is fairly tough paint; acrylic when used with hardener can be color-sanded and buffed to look like lacquer; it's more durable, a little less expensive; and only about 35% goes up into the atmosphere when sprayed. It also resists chalking and is available in more colors than the other paints. The down side with alkyd is that it should be sprayed in a paint booth and baked on with heat lamps; and, having a very slow drying time, both enamels are susceptible to runs and are harder than lacquer to apply.
Application: The first rule in any paint system, is to stay with one manufacturer's products. Recently, I was painting a panel with Dupont Centari acrylic enamel. I had used MarHyde hardener and Dupont's second line Nason reducer together before, with no problems. Having them on the shelf, I mixed everything correctly (Dupont recommends 8 parts paint, 1 part hardener and 2 parts reducer, but I have mixed a 50/50 paint and reducer many times with no problems). I sprayed on the tack coat and it looked fine, waited 10-12 minutes flash time , then painted another coat. As I watched, the paint developed small, clear blisters called solvent popping . This can be caused either by trapped solvents in the top coat, or by incompatible manufacturers products. I had to strip the panel, prime and repaint. The next time, I used all Dupont products, made specifically for the Centari system: 1. Prepsol (wax remover) 2. Centari paint, 3. Centari hardener, and 4. Dupont s slow drying (for hot weather) reducer. The paint turned out great! It just proves, when you know what to do--do it! Don't try to cut corners for convenience. Go to the paint store and get the right products.
To apply lacquer: Use lacquer primer and lacquer-based body putty. Two-part primers and putty dry at a different rate than the lacquer, causing cracks in the paint later on. After priming, sand the primer with 400 grit (400 is coarse enough for the paint to bite and fine enough for a smooth finish). Wipe off with wax remover (Prepsol from Dupont; Acryliclean from PPG), then tack rag and spray. Mix lacquer 100% paint to 150% thinner. Hold the spray gun 8-12" from the surface using 35 lbs of air pressure at the gun. Too much pressure will cause the paint to orange peel. Use a medium temperature thinner for the first coats, keeping the gun parallel with the panel (don't fan at the end of your stroke). Put on two double coats with 50% overlap on each coat. Use the manufacturer s recommended flash time between coats. Paint left to right, then right to left, then follow with another double coat. I put on three double coats with medium thinner, then one double coat with a slow-drying thinner (same mixing ratio). This allows the final coat to dry more slowly, giving a smoother finish that is easy to sand and buff. Anything fewer than 7 to 8 coats, I find, might cut through to the primer when buffing, necessitating repainting. After the last coat, the finish should be uniform and semi-glossy with a little texture. The paint will become very glossy with buffing and the texture will disappear, leaving a shiny, deep, smooth finish.
Applying enamels: Alkyd enamel should be sprayed in a paint booth with heat lamps to bake the paint on. Air pressure at the gun is 55 lbs, and the paint is applied over the manufacturer s recommended primer. Acrylic enamel can be applied over lacquer primer and some two-part primers and two-part body putties. Mix the paint as mentioned earlier, strain and set the air pressure at 55 lbs at the gun. After tack-ragging, I apply a tack coat, moving the gun from left to right, then right to left, overlapping 50%. It is important to let the first coat flash (about 15 minutes, or time specified by the manufacturer) to let it get just tacky enough to accept the next coat of paint without sags or runs. I apply the gloss coats with 2 or 3 double coats, with flash time in between, holding the gun about 8-12" away from the panel (12-15" for metallics). After the paint is applied, I wait at least 48 hours to color sand and buff, and a month before waxing.
Finally, and this is crucial, find a paint supplier who loves old cars. Someone who can not only advise you on the right system for your needs, but can mix paint to match the color you want. It takes a lot of work to prep and paint a car, so the color must be right! We have several suppliers for lacquers, but have found that for special mixes in the Dupont line, there is no one better than Pam Oliver at O'Reilly's in Soddy, Tennessee. She grew up around cars and has the experience and passion it takes to get just the right mix. We ve had everything from Packard Blue (a very dark, almost black, blue) to a 1941 Packard French Gray Metallic that was unusually tough, because it had a green component in the original formula that is no longer available. Pam found a substitute in modern paint, and it turned out great! This has happened to many of the old '30's and '40's colors. Some of their components have been outlawed by the EPA and it s hard to mix them in the new paints. Pam advises spraying your color sample on metal to get the most accurate match. If the sample is sprayed onto cardboard, the computer analyzer sees the color of the cardboard through the paint, resulting in an inaccurate match. Ideally, a 6" x 6" sample is best, and check your color match under sunlight; fluorescent light will not show you the true color tint. When the color is finished, Pam prints the formula and attaches it to the can for an exact match next time!
Knowledge of automotive painting and application is important whether you are going to do it yourself, or just want to understand and appreciate what your restoration shop is going through. Thanks to Pamala Oliver and O'Reilly's for a nice visit and helpful advice on keeping our cars looking great! See you next month. Keep 'em driving!
Note: Always use paint respirators, gloves, paint suits and other protective gear recommended by the manufacturer. Read the label on the can.
O'Reilly's, Soddy, Tennessee: 423-332-1251
Dupont Tech Line: 800-3DUPONT
PG Tech Line: 800-647-6052.