"Body Work & Painting"
In our last issue, we finished the panel welding on our '58 Buick trunk. At that time, we were going to use Ditzler K-200 Primer, a two-part primer that fills fast, but has a short pot life. Our Buick had lacquer-based red oxide primer. This primer was discontinued in January of 1999, but Kondar, a lacquer-based but thicker primer, is still available through PPG's Ditzler line. This primer is a faster-filling primer, with longer pot life and does not atomize as much as the old style "Red Oxide" DZL-72. This was sprayed on over the clean metal of the metal-prepped trunk lid. Some filler was needed and was sanded with an air file with 40 grit paper, then a flat hand sander, straight-sanding, then cross angling to insure a flat, smooth surface. To fill in pinholes and around the edges where the body filler met the metal, a body putty was used, again using a lacquer-based putty. Always let this dry thoroughly to avoid shrinkage. We blocked this down with 280, 360, and 400 wet or dry sandpaper, cleaning the area with water to prevent cross-contamination between grit changes. (The previous, coarser grit would tend to cut into the new work you are doing with the finer grit). After that, a new coat of primer is sprayed on, giving a straight, smooth surface free of pinholes. Multi-light heat lamps were placed at one side of the trunk lid to help accent any high or low spots in the metal. None were found-we were ready for paint!
The color was "Classic White", a 1972 Corvette color that matches the white on the Buick. This was mixed in acrylic enamel. We mixed our color building coats 50% paint and 50% thinner, then added 4 ounces per quart of hardener, and mixed the color with "Smoothie", which helps prevent fish-eye and enables the paint to flow better. The paint is strained and put into the gun, then shot at 55 pounds of air pressure at the gun, about 10" from the surface of the metal. The key to painting is to establish air pressure, material flow, gun speed and gun distance. So, a little practice first will save a lot of trouble later!
Enamels tend to go on and look good for a few minutes, and then start to sag and run. We put on a double coat and allow that to get tacky (about 10 minutes), then another double "wet" coat, overlapping each previous coat, usually building 5-6 coats which allows plenty of paint to be color-sanded and rubbed out later. We think that the closest to lacquer look is to spray 4 color coats, let dry, then wet-sand with 400 (always using a sanding block, as hand-sanding leaves an irregular surface.) Then finish painting with a 40 percent paint, 60 percent thinner mix (with hardener). Don't color sand, just rub out. This gives a smooth, slightly textured, glossy surface with no sand scratches. Two terms to remember are: "Triggering" (good), which means releasing the trigger at the end of each stroke to avoid paint buildup, and "Fanning" (bad), which is turning the gun outward as you get to the end of your paint stroke. Fanning must be avoided to insure a uniform finish. If you do get a run or a gag, LET IT DRY! Then sand it out with 1200 grit and rub it out, if it is a small run. If it is too large, sand it out with 400 grit and repaint the area. It should blend right in. We always use all protective gear, and remember that paint can be absorbed through your skin! Next week, we will rub out the trunk lid and put it back on the Buick. Keep 'em driving!