How to paint a Car
Painting Instruction and Tips
Taking your time and properly preparing the surface is the first step in achieving success.
You cannot get high quality results without high quality preparation. Unlike house paint auto refinish paint hides nothing. If anything, the high gloss clear coat system magnifies imperfections.
Before sanding, affected surfaces should be washed with mild soap and water. After drying, clean with some form of wax, oil and grease remover, often know as Prep-Sol. Prep-Sol removes road tar too. The best procedure is to use a clean lint free wipe to apply the Prep-Sol wet to approximately one panel at a time. Allow the liquid to work dissolving wax and contamination for a few minutes. Then wipe off dry using a fresh, clean wipe. If the Prep-Sol is allowed to dry on the surface before wiping dry the contamination will remain on the surface and the process needs to be repeated. Contaminated wipes are not to be used over again in paint processes. Prep-Sol is not to be used on sanded surfaces. If a solvent based cleaner is desired on a sanded surface there are products made for that purpose.
Products with silicone in them, typically aerosols like carb cleaner, brake cleaner, Armor-All etc. cannot be used anywhere near where painting processes are performed.
Sanding Existing Painted Surfaces
Sand out imperfections using more aggressive sandpaper. If the resulting surface requires primer, the final scratch should be no coarser than 320 in wet-or-dry sandpaper. Areas to be sprayed with color should have a final scratch of no coarser than 600 wet-or-dry. Areas to be sprayed with clear only, as in blend areas, call for a final scratch of no coarser than 1000 wet-or-dry. For purposes of selecting sandpaper grits metallic, pearl and base coat colors are more apt to show sand scratches than solid and single stage colors. After primer has been applied, usually 2-3 coats, wait a minimum of 2 hours before sanding. The exact waiting time is a function of primer build up and temperature but there is no harm in waiting overnight.
Sanding Replacement Parts
New aftermarket or OEM flexible parts like bumper covers are usually sanded with a gray scuff pad, sometimes in combination with scuff paste. That would be followed by washing with soap and water, drying, and spraying with an adhesion promoter before color.
Replacement sheet metal parts are almost always coated with satin black e-coat. E-coat is a rust inhibitive coating that color will not stick to. It should be sanded thoroughly with a red scuff pad and primed. Gray scuff pads are approximately 800 grit and red are 400 grit.
After priming the e-coat sand the primer with 600 wet-or-dry or a gray scuff pad.
We stock several colors of primer to go with the intended topcoat color. Coordinating the colors allows for faster coverage and improved color match.
If you are painting previously painted surfaces either plastic or metal, and the existing finish is sound, as in a good clean used part, just clean and sand for new color.
Obviously mask thoroughly before priming. I prefer to "over" mask to protect adjacent surfaces if possible to avoid spraying primer to the edge of repairs. Primer builds up quickly and it could contribute to the ledge or stair effect created at the perimeter of a repair. Professional repairs are usually masked at least twice, once for priming and a second time for color application.
Start by outlining the repair area with ¾ inch tape. Extend out from there with a minimum of 12 inches of masking paper with more ¾ tape attached to that outline tape. Tape up the 12 inch masking paper end seams too. Always attempt to disguise the refinish areas with creative masking like folding back the 3/4 tape length wise at corners or body style lines. This helps create a soft edge on lines where light reflection helps disguise color match and edges. 3M Door Aperture tape is made for this. 3M also makes pull back tape to go under rubber seals to lift and mask them like around glass. 3M Fine Line tape is used to form radiuses and two tone edges with out the crepe, texture consequences of conventional masking tape.
Understanding that it can be very costly in time most high quality refinish work is done on parts prior to their installation on the vehicle. This procedure is the best way to replicate factory paint work. On a smaller scale this could mean painting a door handle, gas cap door or rear view mirror off the vehicle.
Use a decent grade of fresh automotive masking tape to avoid adhesive to substrate transfer.
Priming Flexible and Rigid Plastic Surfaces
A book could be written on painting flexible plastic parts. Mostly this relates to flexible bumper covers. Part of the problem is the variety of different plastics used, many calling for different preparation procedures. For the most part, when rigid or flexible parts, typically bumper covers, are being repaired, if the bare plastic is soap and water clean, sanded with a gray scuff pad, and sprayed with adhesion promoter per the directions on the can, color will stick.
If, however, you are installing a new front cover on a late model vehicle we need to develop a more comprehensive plan addressing stone chip resistance and flexibility. In a nutshell adhesion equals flexibility and greater levels of adhesion can be obtained by using selected 2 component products.
In the case of putting new color on previously painted plastic and flexible parts, like used parts, no special attention is needed, just clean, sand, and apply color.
Priming Metal Parts
For bare steel, aluminum, or galvanized surfaces, spray self etch primer on the larger exposed surfaces.
In the case of e-coat as discussed earlier, re-prime the e-coat with hi-build primer as needed and sand for color. Again, if existing parts have sound flawless finishes there is no need to prime them, just clean, sand and spray. The exception would only be to assist in coverage in the case of a dramatic color change, for instance changing a used red part to white in which case you may want to quickly prime with light gray.
Spraying the Color
Shake can thoroughly. Spray a test panel in a uniform pattern. Make a mental note of the coverage characteristics of the color. Determine the suitability of the color match. In the case of base coat you may wish to clearcoat the test panel to determine the suitability of the color match. If it is unacceptable, stop and call a clergy person and then the store.
If the color is perfect or "blendable" it is considered to be acceptable to spray.
Spray color in a deliberate organized east-west pattern, overlapping each previous pass by ˝. This is known as one single double coat. The first coat in particular should be no more than a medium coat. Very heavy wet coats, especially with metallics are never advisable. You should be able to see through the first coat if not both the first and second coat. It may be possible to alternate coats between an east-west pattern and a north-south pattern. On a larger horizontal repair this may assist in metallic-pearl orientation. You will probably need 3 to 4 coats of color depending on the color, the color of the substrate and your spray technique.
Do not sand between coats other than to scuff out a minor unforeseen imperfection.
Allow each coat to flash off. That is, for the surface solvents to escape. In the case of single stage you will be able to brush the masked, oversprayed surface adjacent to the repair with the back of your fingers without sticking. In base coat the surface will change from wet and glossy to a satin level of gloss. Sufficient base coat should be applied to obtain hiding. Excessive coats provide no value. Base coat dries to a matte finish, it has to be clearcoated for gloss and durability. Single stage is applied to achieve coverage with possibly one extra insurance coat.
Total coverage will probably be achieved in 3 to 4 coats.
When in doubt, wait longer between coats. Excessive material applied too rapidly will have a tendency to dry slowly and take an impression, for instance thumbprint, the following day.
After the last application of base coat has flashed apply the clear. About 2 to 3 coats usually, definitely 3 coats if planning to scuff and buff.