a.    Introduction.

When doing a small repair, or preparing a whole vehicle for painting, there are certain steps and procedures to do. First, the vehicle must be assessed for what body work is required. Have a look for rust, dents, large scratches, etc. It may be wise to replace a panel rather than trying to repair it. Rust will always come back no matter what, so replacement of rusty parts is necessary on a quality job. Minor scratches will be sanded out, but larger ones will need to be filled. Dents should be banged out as much as possible without overstretching the metal beyond the rest of the panel, so that minimal filler is required. Once the vehicle is assessed, all ornaments or items that will be in the way of the paint job should be removed: pin striping, mirrors, bumpers, window trim, lights, moldings, etc. But whatever is removed must be replaced after the paint job, so only remove what is necessary, and take note that replacing these parts may cause you to scratch the fresh paint. Also, before proceeding to do any work, make sure that the vehicle is clean. We want to prevent chemical contamination with the primer and paint (from wax, grease, hand prints, etc.) and remove and dirt/dust that could blow off the vehicle with the paint gun into the wet paint. You may buy silicon wax remover solvent, in which you soak a wet rag, wipe the vehicle, and the wipe dry with a clean rag then wash vehicle with water. Personally, I find washing the vehicle with a heavy-duty dish detergent (like Sunlight, or Dawn) does just as good a job.

    b.    Sanding/Sandpaper

There are many different types of sand paper, and the right product makes the job easier. Sandpaper is sorted by "grits" (the number of sand particles per square inch). The fewer the particles, the larger and coarser they will be. Rough sand paper (60, 80, and 100 grit) is used to sand body filler, and cut through paint to bare metal. Medium grades (120, 180, 220) is usually used for sanding minor imperfections, and finishing putty. Fine paper (320, 400) is used for finish sanding the whole vehicle before primer or paint. Finer papers (such as 600, 800, 1000) are used after base coat before clear coat, if this method of base/clear is used. Super fine papers (1200, 1500, 2000) are used in detailing a vehicles paint when cut polishing a new paint job, or refreshing an old paint job.

There are different methods of sanding: by hand, by hand with a block, or with various machines. Using a grinder or a machine to grind metal prior to applying filler is acceptable, but all other sanding results in a better finish if completed by hand. Use of machines can leave swirl marks, and even wavy finishes down the side of a vehicle (even when used by some professionals). When trying to sand something to be smooth, always use a sanding block (as long as possible). When finish sanding an already smooth surface, always sand using the palm of your hand. Sanding blocks should be as long as possible to prevent a wavy finish. When sanding filler it isn’t too important what direction you sand in, but finish sanding can make or break a paint job. Finish sanding should always be done in the direction that the painter is going to paint the vehicle (generally front to back) so that it is less likely that anyone will see any sanding marks through the paint. DO NOT sand in various directions, swirls, or at intersecting 90degree angles; this is wrong for finish sanding. (Note that when finishing sanding before painting, it is essential to sand cracks, grooves etc, so that the paint won’t peel off, such as the end of a fender or door, around rubber trim or molding, in the lip if the wheel well etc.) Another point on hand sanding is wet sanding. When sanding by hand, water can be used as a lubricant, and can actually speed up the sanding process. The best method is to saturate the sandpaper (and block if used) and the area to be sanded with water from a clean plastic squirt bottle. The water lubricates the surface, and washes away the sanding dust, so that the paper cuts better and the paper lasts longer; however, you must use a wet/dry paper, and may only sand surfaces that are safe to get wet. DO NOT wet sand fillers, or porous primers, such as lacquer primer.

    c.    Welding Holes

Neither rust nor holes should be covered with filler. Most fillers are hydroscopic (they absorb moisture/water) so the exposed side of the filler over the hole will suck in water, expand like a sponge (creating bubbles) which allows the remaining sheet metal to rust out worse than it was. To prepare for welding, all the rusty metal must be cut out with an angle grinder, die grinder, or whatever tool is deemed appropriate. It is wise to cut an extra few inches around the affected area since the surrounding area has probably begun to oxidize. Using sheet metal (I prefer 20-24 gauge satin finish steel) make a patch that surrounds the hole by at least ¼". Now using a pointed hammer, bang the edge of the affected area enough so that the patch will sit slightly BELOW flush. I suggest this because most people aren’t going to be able to make this patch 100% smooth and seamless with out a few thin layers of filler. Now grind down to bare metal at least 1" around the area to be welded. Weld the patch in place well without burning holes through the sheet metal. Once welded, grind the welds fairly flush with the surface. At this point you should be able to read the next section on using body filler.

    d.    Body Filler

There are several different types of body filler. Typically you only need to use two products. For filling small dents, and imperfections, or smoothing out patches use a lightweight filler (the most common filler available). For finishing jobs use a finishing putty. Both of these products have to be activated, or else they wont harden. Most lightweight fillers are the same, and any will do the job. When it comes to finishing putties, there is a huge difference in the product, and the proper product could save you hours, and a little bit of money. My favorite putty is USC’s Icing. Lightweight filler is good for dents about ¼" deep, and icing is good for 1/8" or less.

When a repair is ready to be filled, it should be ground to the bare metal (or on top of a previous layer of itself) with a grinder, or coarse paper (80 grit or less). The product should be used as per the manufactures directions, and applied over the area. It is best to work quickly, and in small sections at a time, overlapping the area some, so that blending is made easy. Apply the filler as smooth as possible, and don’t be upset if you have to do it three times before the area is finally filled properly. Wait for the filler to set (usually 20-30 minutes) and block sand smooth with 80 grit paper making sure that your sanding block is larger than your patch (if possible). Repeat this process until you are satisfied that the area is filled, and it blends smoothly with the rest of the body.

The finishing putty can be used now to fill the coarse sanding scratched or pin holes from the body filler, and can be used anywhere on the body where minor dents or scratches remain that are less than 1/8" deep. Prepare the area by sanding with 120 grit paper, and mix the product as advised my the manufacturer. Apply the product on as smoothly and quickly as possible, as most finishing putties set in a matter of minutes. Once hardened, sand with 220 grit and a block at least as big as the patch (if possible) and repeat until the area is perfect.

A few notes on filler: When waiting for the filler to harden prior to sanding, press it gently with the fingernail. When the fingernail no longer marks the filler it is ready to sand. When finished applying the filler, clean your spreader and mixing plate with lacquer thinner before it hardens so you can reuse your tools indefinitely.

    e.    Preparing for Priming

Once all the above-mentioned bodywork is completed to your satisfaction, you can prepare for primer. You will want the whole vehicle to be sanded with 320 grit paper (including edges, wheel well lips etc), and anything necessary to be removed from the vehicle. Now the vehicle can be taped off. Make sure to use a quality masking tape (such as 3M) or else the chemicals of the primer could eat through the tape. I also recommend buying a roll of masking paper. It is fairly cheap, and much easier than using dirty newspaper. First tape the edges of everything with a narrow masking tape (about ½" wide). Now using a sharp razor blade, cut the masking paper to the size and shape of the areas to be masked, and tape in place making sure there is NO way the paper or tape could come up. When taping around the rubber trim of windows, stretch the tape with one hand, and apply the tape under the trim with your finer nail (or use the dull side of the razor blade). Once the whole car is masked off to your liking (including wheels) spray the vehicle with compressed air to remove any unknown dust and to see if any tape or paper blows up. Now you are ready to prime.

    f.    Priming

There are many different brands and types of primer to use. You should use the same brand of primer as you are using for paint to ensure compatibility, and double check with your supplier, that the primer and paint are compatible. Different primers do different jobs. Some to be aware of are Epoxy Primer (for use on bare metal, fillers, aluminum etc.), 2k (urethane primer, used these days as a general-purpose primer; it’s good because it can get wet, so you can safely drive with it applied and even wet sand it), and lacquer primers (not used much today, and I suggest avoiding if possible; its advantage is that it can be sanded 30 minutes after it is applied). Many primers will say the word "surfacer" on the container; this means it is a sandable primer. Most primer surfacers are "high build", which means you can apply many coats to hide minor bodywork flaws (sand scratches, grinder marks etc). The bottom line is that primers are used to make the paint stick to the vehicle. For future reference, if you are repainting a vehicle that has good paint on it and there is no exposed metal, you can probably paint over top of the old paint with out priming it (so long as it is sanded properly).

    a.    Introduction to Painting

You will want to ensure you have all the proper tools for the job. A good air compressor, generally of the 5 or more hp variety, and can produce much more than 5 CFM@40 PSI. You will want a water filter to be fitted at the gun and/or the output of the compressor. A good automotive paint gun (not a household paint gun) is necessary. It is best to use a separate gun for priming from what you use for painting. A quality automotive paint is necessary, as well as the appropriate chemicals, and a cleaner for the gun.

    b.    The Paint Gun

The selection of a paint gun is essential. You can buy cheap paint guns at many discount tool stores, and some will work well, but will not stand the test of time. There are essentially 3 types of guns: conventional (siphon feed), gravity feed, and HVLP. Conventional guns are great, and fairly easy to use, but require more air volume than the other two, and a slightly higher PSI (usually the 45-55 range). Gravity feed guns feature the paint canister on top and require a PSI in the range of 35-50. Many gravity feed guns are mislabeled as HVLP. Gravity feed guns are simple to use, and tend to give a great finish, no matter what type of paint is sprayed. HVLP stands for high volume, low pressure. HVLP usually operates below 10PSI, but requires a large volume of air (often more than 15 SCFM). True HVLP guns are the best, but are expensive (usually cost between $700 and $1500 for a quality gun). The photo to the right is a gravity feed gun.

Another important factor in the gun is the nozzle and jet size. All guns can be changed with new sized nozzles and jets ordered from the paint gun’s manufacturer. Nozzles are usually measured in mm. The best nozzles for painting modern paints range from 1.4-1.6mm: for priming, 1.5-1.8mm.

When it comes time to paint, there are many adjustments that need to be made. Air pressure is first. Usually the paint manufacturer gives recommendations, but fine-tuning to your liking is essential. Additionally, there are 2 (sometimes 3), adjustments on the gun: air/product mixture, spray pattern, and (optionally) air control. The air/product mixture is usually located at the rear of the gun, directly behind the needle. It controls the ratio of air and paint exiting the gun. The pattern adjustment is located near the air adjustment on a conventional gun, or on the side of the gun on gravity feed units. This adjustment changes the size of the spray pattern from narrow to wide. If the gun is equipped with an air control valve, it is located on the stem and can be used to limit the air pressure, rather than having to go all the way back to the compressor to adjust it. This is often referred to as a cheater valve. All these adjustments should ALWAYS be checked before painting the vehicle. Also, some painters may decide to adjust the gun at any point during the painting process. Do so if necessary, but be careful not to ruin the vehicle’s paint job.

After painting it is essential to properly clean the gun, otherwise the paint may seize the gun useless or allow dried particles to ruin the next paint job. To clean the gun, first put an ounce or so of lacquer thinner into the paint cup and spray it through the gun. Then disconnect the paint gun from the air fitting, and begin to disassemble it (the paint gun should come with a manual describing its specific procedure). Once all the parts are removed, carefully wipe off all paint with the lacquer thinner, and wipe clean with paper towel or a rag. Once the gun is cleaned free of all products, and it is dry, reassemble the gun for its next use. Check the paint gun's book, as there may be some necessary lubrication.

    c.    Paint and Paint Products

There are many quality brands of paint. The big 3 paint manufacturers each offer a high quality line and a budget line of paint. The budget lines of paint are excellent paints, create excellent savings in price, and are generally easier to use. PPG is the world's largest manufacturer of automotive paints, and makes most original finishes for the automotive manufacturers. PPG's discount line is called Omni. DuPont seems to be about the same quality as PPG, and its discount line is called Nason. The 3^rd largest paint manufacturer is R&M; their discount line is called Limco. Other manufacturers include Sherwin Williams and House of Color.

Regardless of brand, there are different types of paint that reflect different qualities. Lacquers are one of the oldest paints and easiest to use. They dry very quickly, and provide excellent deep gloss. Lacquers are less common today. There are many types of Enamel paints available, but the most common is Acrylic Enamel. It is a hard paint, and does NOT provide the best finish in the hands of a novice. A paint of better quality that is similarly priced to Acrylic Enamel is Acrylic Urethane. It is a modern deep-gloss paint that provides a durable chip resistant finish that is somewhat simple to use (highly recommended for the beginner). The single most common paint today is base coat, clear coat (B/C). It is a polyurethane based paint that may contain trace amounts of enamel (or lacquer in the high end brands). B/C has been applied to most vehicles at the factory since the early 80s. It is most expensive, as both paint and clear coat are required, so that it is necessary to buy more product. B/C is easy to use, however, provides possibly the best finish, and is the most versatile. It also is the most protective, as there are several clear coats protecting the paint from exposure.

Single stage paints (all paints that are not base, clear) are used principally in the same manor. There are 3 products that need to be mixed (paint, activator, and reducer). A formula from the manufacturer will say how much is to be used in that order (i.e. 8-1-4 means 8 parts paint, 1 part activator, and 4 parts reducer). One the paint has been activated, it must be used within a certain amount of time (usually a few hours). The paint is then put into the gun, the gun adjusted, and sprayed with a light first coat (not heavy, you may barely notice the color of the new paint), then a second coat which will just about cover the vehicle, and finally a 3^rd coat to finish it off. It is okay if more coats are necessary.

B/C paints are mixed with 3 or 2 parts: either 3 parts, (just like single stage) or a 2-part system (as in DuPont's ChromaBase system w/o activator). Once the paint is mixed, it can be applied within a certain amount of time (except systems such as DuPont's ChromaBase w/o activator, which has an indefinite life). Solid colors may be applied with only two medium coats. Metallic, or hard hiding colors (such as reds) may require 3 or more coats. Once the paint is complete, it is time for the clear coat. The clear coat can be applied 15 minutes after the paint or no later than 24 hours after the paint. Most clears are mixed 2 parts (often 4 parts clear, one part activator). The clear can be applied in as little as 2 coats, but I recommend at least 4 medium coats. Be careful when painting clear, as it is hard to see, so accidental runs are easy to achieve.

All activated paints become chemical resistant and dry due to the activator. The activator gives the paint its hardness, and partially contributes to its deep gloss (except for base coats of B/C which dries to a matte finish). When buying paints, you will have a choice of slow, medium, or fast reducer. These are variants, which depend on the temperature when being painted. The colder the temperature, the faster the reducer you want, however slow reducer will allow a smoother, more blended finish. Too fast of a reducer will cause a rough (possibly non glossy) finish; too slow a reducer may cause trapped reducer in the paint causing off color streaks and possibly small bubbles in the paint several months later. Ask your paint supplier for the recommended reducer if you are unsure.

    d.   How To Paint

This applies to both single stage and base clear paints. Make sure that the vehicle is clean of all dust and contaminants (grease, wax, fingerprints etc.). Ensure all safety equipment is worn (chemical respirator, gloves etc). Start painting the roof with a very light coat, holding the gun about 14" from the vehicle. This coat will not cover the primer, but will leave a light color (see photo on right). Work your way over the whole vehicle moving the paint gun in the direction that you sanded (probably front to back). Use long overlapping strokes and keep the gun at an even distance from the vehicle. Once the entire first coat has been applied, allow a "flash" time of about 5 minutes before applying the 2^nd coat. Start where you began last time, and repeat this coat, being careful that the air hose does not touch the painted surfaces. This coat should start to cover the primer, but it may still show through a little. The lighter the coats, and the more applied, the smoother the finish will be, and it will be less likely for runs to occur. Generally 3 coats is enough, but do not hesitate to do more (the bottom photo to the right is the 3rd base coat). Again, allow a 5-minute (or more, referring to the paint’s tech manual) flash time between coats. A tip for a smooth finish is to add a little extra reducer to the mixed paint, increase the air pressure by about 10 PSI, and spray further away, covering the whole vehicle (do not attempt if you are unsure). Allow the paint dry a little past tack (about 3-4 hours) before removing the tape and paper. Refer to the paint's tech manual to know when it is okay to use the vehicle or apply the clear coats. Most clears can be applied after a 15 minute flash, and NO later than 24 hours. Single stage paints can usually be put back into service after 12-24 hours.

    e.    How to Clear Coat

Refer to the manufacturers tech manual for complete details. Usually after the base coats have flashed for at least 15 minutes, the clear can begin to be applied. 2 coats are usually the bare minimum, but I recommend at least 3, and if possible 4 or 5. The application of the clears is basically the same as the paint. Be very careful not to apply too much in one coat. The clear is difficult to see and therefore easy to produce runs. Usually the paint is non-sandable before clearing, but clear coating after 24 hours will require a light scuffing with a Scotch-Brite pad.

    f.     Finishing After Paint

After the paint has dried over night, the vehicle is ready to be finished. If there are imperfections in the paint they may be wet sanded and polished out, otherwise the vehicle’s paint is finished (although the vehicle may be polished anyway to enhance its appearance, see below). So all lights, trimming, etc. can be replaced carefully such that the fresh paint is not damaged. Moldings and pin striping may be added as well. Ensure everything is replaced and functioning before the vehicle is driven. With the new paint, avoid bird droppings, gasoline, and other contaminants for as long as possible. Although the paint has dried, and is ready for service, it takes full 120 days for the paint to cure 100%. Wash the new paint with cold water, and a mild automotive detergent, then wipe dry with a soft cotton rag to prevent water spots from staining the fresh paint. During these first 120 days, the paint will be more vulnerable to scratching, chipping and staining.

Check with the paint manufacture’s tech manuals for specific details on these procedures first. A high quality polish may be applied to any new paint after it has dried (usually after 24 hours). Only polishes or mild rubbing compounds can be used. Waxes are not acceptable. Waxes may only be applied after 120 days, because waxes contain silicones (and/or lanolin). These tend to seal the paint, and disallow any extra solvents in the paint from escaping (trapping them inside). Solvents trapped in the paint can leave white hazes and more commonly cause small bubbles in the paint, ruining it. So be very careful when choosing a cut polish or rubbing compound. I personally prefer 3M's Perfect-It II (as recommended by DuPont).

If minor orange peel is all that is to be corrected, then buffing will be acceptable; otherwise, wet sanding is necessary. 1500 to 2000 grit wet/dry paper is preferred. Soak the paper well in water, and sand out the imperfections with a sanding block (for runs) or by hand (for orange peel), being careful not to sand any more than necessary. The sanding will dull the paint, but don’t worry. Once all imperfections are sanded out, then it is appropriate to start buffing.