- The part and the materials you use should all be at room temperature. In colder situations, you need to heat your area and ensure the work & materials are similarly warmed up. Cold metal may sweat when brought into a warm area as condensation forms on them.
- Stripping is optional but if you want a high grade finish and do not want to worry about some old finish reacting to new paint, then get yourself a high grade paint stripper and strip the thing. DO NOT use paint stripper on plastics – all you can do is sand. Make very sure you wash all the stripper off the part before going further.
- At very least, use wax remover/grease remover on a part after preliminary washing. Do this before sanding so you don’t grind contaminants into your finish. NOTE – from here on, it’s best to NOT use wax & grease remover for wiping, use only isopropyl alcohol (aka rubbing alcohol available at pharmacies). This is because the wax & grease remover can penetrate fillers. Isopropyl alcohol will evaporate.
- Keep your bare hands off the work! The oils from your skin can cause adhesion issues when you paint. Don’t do like TV shows where someone’s rubbing their hands on a vehicle or part. Wear clean nitrile type gloves!
- The best barrier coat over old finishes and on bare metal is epoxy primer. There are many brands and you MUST read and talk with suppliers so you get the right material for your needs. Some older type Epoxy primers, despite the name, are a non-sandable sealer to be applied to bare metal and old finishes.
Epoxy is applied before you use any filler products. You need to be careful when sanding the filler materials that you don’t sand through to bare metal. But it’s not a killer if you recoat, over any new filler and to cover any accidentally exposed metal. The whole idea is that typical “bondo” fillers absorb water and tend over time to cause rust if they are applied directly to metal. - However, if you’re working on a modest budget or just trying to get a decent daily rider finish, so long as you’ve paid attention to wax/grease removal, you can certainly get a decent product that will last years, if you simply use a good quality primer, then filler. On raw metal, use an etching primer that will adhere best to bare metal and otherwise just use a good quality sandable primer.
- When sanding filler, it’s best to apply a thin dusting of cheap flat black spray can paint once you have the filler rough shaped. Sand as much as you can using some sort of sturdy but flexible backing pad appropriate to the shape of the area you’re working on. This process is called blocking. Watch for any black areas that never sand off. These are low spots. Fill/prime and keep going until you’re satisfied with the finish.
- Once you have stripped or sanded, primed and filled, apply at least one coat of sandable primer. Epoxy based sandable prime is best. Though expensive, this further protects against moisture penetration.
When your work is done to your liking, it’s time for a final prime or seal coat and light sanding. Follow the directions to thin down your prime to use as a sealer but if you’re using rattle cans, so long as you have smooth even finish, wet sanded down to 400 grit, you’re all set for color. - Here’s just a few quick notes about “built-up” finishes, regardless of the equipment you use.
If you want to achieve a metallic or metal flake finish, you will need to consider what base you use, even with rattle cans. A “chunky” silver will make a good base for most transparent <aka candy> color topcoats. With flake, black is the best base, then apply the flake, then the candy. You have many options. Usually you apply the base color, then according to the manufacturer’s directions, apply intercoat clear used to separate layers of materials, it dries fast but if you later add a graphic or something that turns out wrong, you can carefully sand it away, down to the intercoat, instead of risking damage to the base coat, although with a full flake finish, you’d probably just mix the flake with your intercoat. Intercoat is no good as a finished top coat but it’s ideal for a cheap barrier between color and striping and/or graphics.
Another way of adding flake is to use an old-fashioned routine, lay down your base and sprinkle the flake out of a spice dispenser with the shaker top. It takes some practice and it’s messy, but even shooting flake is messy! It sounds crazy but early custom car and bike builders like Ed “Big Daddy” Roth did this and got great results.
If you want to use masking to create graphics or to divide two colors, etc., here’s a very helpful thing I learned. Don’t use any ‘fine-line’ fiber type tape like typical masking tape. You ‘can’ but you MUST burnish the edges to ensure you get no ‘tape bleed’ where paint makes a fuzzy line because it can creep in under the tape edges. Two steps can make life easier – use plastic fine-line tape and don’t stretch it or it will change it’s shape and then once applied and burnished lightly, and then, if you’re using automotive materials, lightly spray the tape edges (if you have an airbrush, that’s a great tool for this!). This will fill any ‘tape bleed’ areas with clear and stop any later color applications from getting under the tape edges. However, you must remove the tape while your finish is still curing or you may tear out finish. Sound tricky? It is, that’s why high quality painting involves not only good materials but also a person with skills developed over time.
If you use rattle cans, you can apply your color coat, then perhaps a spray can glitter, then clear coat it later (more on this step below).
For all products of any type, read the manufacturer’s recommendation for curing & recoating times (including how long to wait if you want to use tape for the next step), and when/if you need to scuff the finish before the next coat. - If you spray color from rattle cans, use thin dust coats. Do NOT try to get good coverage in one coat. Plan on three coats, spraying in different directions, to achieve a complete finish.
Rattle can paints are far thicker than automotive spray finishes. If you throw on too much, too fast, you will get runs.
Application with ‘real’ automotive products is a similar routine, keep the coats light with successive coats with a change in direction of travel. - Note there’s a clear deviation between rattle can vs. automotive products.
Rattle can products are very thick compared to automotive products. You MUST let rattle can products “cure” long after they are hard to the touch. I’ve coated Rustoleum products with automotive urethane clear with no problems. After a few poor test patches on an old tank, I consulted a local automotive paint guru. His advice, even in hot sun, the rattle can stuff must cure for a couple of weeks. I followed that advice, then cleared over my Rustoleum and it came out fine and it still looks good after several years.
Automotive products are a bit different. If you’ve read the succession of steps above, note that with automotive finishes, you can usually lay down base color, effects if used, candy top color, and then clear, all in one sequential flow.
Spray can and automotive product makers provide ‘recoat interval’ information. Follow it carefully. - Of course, this page is a very brief explanation of the process. There’s tons of videos online. If you choose to work with automotive finishes, I strongly recommend that you work with an automotive paint supplier. Take notes.
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