WANTING A LATE model finish on a custom car can seem dim. Indeed, a modern clear coat can put the final touch on a color and protective, high technology beneath the finish. Any automotive refinisher worth road salt will tell you, however, that cars must have good initial protection applied to the vehicle's exterior panels. You first need to properly prepare the base surface! This is done with an anti-corrosion material. If you’re refinishing a modern vehicle, you may find the lower panels are galvanized and many upper panels were treated using a zinc phosphate coating. Throw in the fact that some aluminum and various plastics exist, and you have a complex formula that cooks the minds of many custom car painters.
First know that considerable differences between finishes exist depending on make, model and years of production. Occasionally, changes may have even been done at the factory during mid-year. Know that car makers may have initially covered zinc-coated steel with an electro-deposition primer; or may have used a baked polyester, epoxy, or one-step primer. This was done before they applied a topcoat to the metal. Some foreign car makers, the Japanese in particular, may have used a surfacer as a base for a high-solids, solid-colored paint. Then these were followed by a three-step paint system, using a clear topcoat that included tinting.
During the 80’s, some Ford plants laid on a polyester base coat paint followed by an acrylic clear coat. As well, a few 1980's vintage GM cars may wear a waterborne enamel. You may also find a high-tech polybutyl primer covered by solid color alkyd enamel flavored certain European finishes. During that era, car makers went toward the use of a metallic, high solids-low solvent coating… or water-based lacquer basecoat followed by a polyurethane clear coat. Exotic formulas became the taste for many car makers in order to comply with Federal EPA regulations. As of 1988, finishes became enamored with three-stage paints. These were built using pearlescent solid base coat colors over-coated with clear paint that contained mica-flakes. A final clear coat topped the cake for a very deep, pearlescent, high gloss luster.
You can see that when in the restoration arena, we've got to cook up a duplicate of all this special flow and reflow, computer-controlled, robot-applied hi-tech… using a pot, a mixing stick, and a hand-controlled spray gun. We then throw-in some simple air-drying or surface heating magic with infra-red technology. Unless we plan the job, these differing technologies can quickly ruin the look.
Additionally, today's automotive refinishing materials spray as water-based materials from low pressure guns that atomize liquid droplets. These droplets quickly convert to hard, durable films. The products depend on evaporation to dry.
Paints, primers, primer surfacers and such. . . normally contain three components. First, pigments are responsible for color. Next, binders are the chemicals that form the film, Lastly, solvents keep the whole concoction a liquid while you magically do the application. However, like when making tasty soup or stew, you must use good ingredients.
For example, strong latent solvent provides a good gloss. Many color cooks get sloppy right away with solvents. A mess can occur in a topcoat because of too slow, latent solvents. Since a cheap thinner has weak latent solvent it causes poor gloss and adhesion. Poor solvents also may cause cracking, dull finish, chalking, cracks or splits, blisters, sand-scratch swell, blush, pinholes, and most of all... a poor color match is likely for repair jobs.
Be aware of... and obey local, state and federal regulations concerning all spray evaporative emissions!
Be aware of... and obey local, state and federal regulations concerning all spray evaporative emissions!
Consequently, if you inadvertently mix cheap thinner used for cleaning a paint gun into your primer coat, that poor solvent dries too slowly. Thus your topcoat is usually affected. A quality thinner contains a balanced mix of active and latent solvents and certain diluting liquids.
Know this! Active solvents blend with a latent solvent to give drying control for the spraying of lacquers and enamel. Each thinner or reducer is uniquely rated for a given range of refinishing needs. Therefore your solvent should always match spraying conditions.
Your binder can spoil the pot too. Primer and paint binders can vary widely from simple nitrocellulose lacquers to alkyds, acrylics, urethanes and polyurethanes. Obviously, when you use these, we recommend using a whole system of matching products. Follow exact formulas to ensure proper chemical reactions. Color matching can be difficult at best since a myriad of distinct base pigments now exist to reproduce factory colors.Take note that the use of these may be restricted, or downright illegal in a given setting.
Metallic, mica, and pearl flakes of various sizes are now available. Though metallics and micas must contain additives to prevent mottling, if they don't settle just right your car can look like a chameleon, tiger, or zebra. Also, if you choose to use a factory pack premixed at the paint supplier, you should have tinting knowledge.
If you choose a mixing system using base colors, follow the exact mixing formula recommended. Also remember! If you’re going for a factory restoration, use a quality refinishing system designed to match, but not necessarily duplicate, various original finishes. Be careful here! Some car show judging asks that a vehicle be refinished in the exact materials of the original coating! However, for the Sunday ride to the local show, go for long lasting and best results. Work from the metal up with products from a single refinishing product manufacturer.
If you're starting with bare metal that's not galvanized, first remove all rust, oil, grease, and water. Don't prime untreated metal! Condition the surface. Mix your metal conditioners and let the conversion occur according to the material's recommendations. Afterward, make sure you rinse the surface thoroughly with clean water. A brownish-hued coating should remain on the surface.
To apply your primer, you have several choices. Nitro-cellulose primer derives from natural cellulose. This primer has good adhesion properties, but poor anti-corrosion and filling. You may instead choose zinc chromate or vinyl-wash primer applied prior to a primer-sealer or primer-surfacer. Vinyl wash primer consists of two-components-the primer. . . and a plasticizer. Just know that this stew has a limited pot life. If not applied within the recommended time, you must redo the mix. Also know that the use of these chemicals demands a sure knowledge of personal contact and inhalation protection!
Epoxy primers are also two-component materials used for priming aluminum, steel, galvanizing, plastic fillers, and fiberglass. Also, know that you can also use an alkyd enamel primer-sealer under enamel topcoats.
If you're working on a flexible part, remember that solvents in the primer may attack the plastic. Wet sand the part using No. 320 or 400 waterproof paper. Use a little very mild soap put into the water as a lubricant. When the plastic surface is smooth and featheredged, apply a water-based primer coat especially formulated for plastic parts. Let the coating dry and sand the surface lightly. Don't break through to the plastic! Lastly, coat once again using a quality primer-surfacer. Primer-surfacers are primers which contain polyester fillers. Many shops prefer using them for steel or plastic priming because they offer better filling of minor surface imperfections. You’ll find most modern primer-surfacers provide previously unheard of filler adhesive properties.
You may find that a nitrocellulose primer-surfacer provides good filling, dries fast, sands nicely, and is great for spot repairs. However, for good corrosion resistance use an epoxy primer, alkyd, acrylic, or urethane primer-surfacer. Use these products for full panel refinishing. However, this stuff won't do well for doing spot repairs because of the short pot life and long dry times. For these, consider a universal primer surfacer that holds up beneath several different topcoats. Consult your paint supplier for recommendations.
Consider using a sealer where chemical incompatibilities may arise. Remember that many old finishes, especially lacquers, are susceptible to lifting because of the attack of strong solvents. However, know that sealers have a recoat time limit. If you fail to recoat the surface in the time allotted, peeling may occur. You can use a high quality sealer beneath most topcoat products.
If you are working with an oldie but goodie, to determine whether the paint is lacquer or enamel, wet a cloth with thinner and rub the paint. If it dissolves after a few rubs it's most likely a lacquer. On the other hand, if there's no color transfer. . , enamel is the ingredient. What kind of enamel, colored or clear? You can detect a clear enamel by sanding lightly on a remote area with No. 220 sandpaper. If this action brings up white powder on the paper, you have a clear coat enamel.
When working with restoration of an old surface, sand-scratch swelling may be a problem for you unless you seal new solvents from reaching the old sanded surface. Examine the old finish closely. If it's cracked, crazed, or otherwise badly damaged, you have to remove the paint. Use a dual action orbital sander with No. 220 paper or a quality paint remover to take it down. NOTE: Always wear a respirator when working with removers! Also, protect your hands by using rubber gloves, and your eyes with goggles. When using a remover, scrape the paint off and wash the panel with water after the old paint lifts. Be sure not to use a remover on plastic, aluminum, fiber-glass, rubber, upholstery, or flexible plastic parts!
Use wax and grease remover after paint removal and before sanding an original primer. Use some tricks from the ingredient bag. If paint damage isn't too severe a hand sanding block or solvent can featheredge a chip. If you’re working with a lacquer, for example, form a small ball using a shop towel. Soak the cloth with solvent. Hold the ball against the surface for a minute. Now rub the spot with circular motion until the metal shows slightly through the primer. Now lightly clean to a featheredge using light, fine sanding. Clean the area with wax and grease remover and mask it off. Once done, prime and refinish sand.
Now you're ready to mix your paint. Follow the thinning/reducing formula exactly when mixing. Be aware that temperatures influence viscosity and drying times greatly. Store paint at room temperature and use a viscosimeter and cup filters during mixing. Add the recommended solvents very carefully! Incorrect reduction can cause excessive orange peel, sags and runs, metallic flip-flop and poor hiding. Wear a positive pressure air-supplied respirator or an equivalent when mixing and spraying. I recommend that you protect yourself and the surface you spray by wearing a painting coverall equipped with a hood.
If used, add all necessary flexers, hardeners, and fish-eye eliminators last. Mix well and then do a color check. Remember! If you’re using a basecoat/clearcoat finish, the base color coat dries with a low gloss and the high gloss comes out with the clearcoat. A color coat-plus-clear coat system on the other hand, is a conventional coat of lacquer or enamel with a clear coat of lacquer or enamel applied over it. In this application the color coat does achieve a gloss, so the clear topcoat simply enhances the finish. Note that in any multi-stage finish, film thickness is critical or cracking may occur.
However, before laying on any coating... if your test panel color isn’t what you desire, before you grab a tinting can and start throwing more color in, realize that many controllable items can cause a tint trouble. The first is application technique! Before anything else, read the instructions again. Is gun air pressure correct? Excess pressures can lighten a color coat; whereas, low pressures tends to darken. Make sure of the proper solvents or reducers. Hot weather or fast dry solvents may also lighten a finish. Make sure of your spray gun settings and the spray pattern. Recheck your spray booth conditions.
Finally, before phoning your supplier, know that color pack paints and paint formulas are usually very accurate to the original, requiring very little tinting or blending. Look to the supplier only when you have checked and rechecked paint application methods. Also, know that paint manufacturers usually have Internet access or troubleshooting phone hotlines. Check them out! They are master’s when it comes to dealing with automotive refinishing.
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