OK, now that we’ve touched on the common sense basics let’s move on to our primary focus—recognizing and addressing the causes of the most common of paint problems. Just keep in mind that I’m just a hobbyist, not a trained paint pro, and this is just info gleaned from asking questions and personal experiences—meaning if you read this and then have a problem of your own, I won’t be coming over to fix it for ya. CT
Fisheyes are small, circular, crater-like openings that appear either during or shortly after you lay down a coat of paint or primer (though primer is often much more forgiving). They’re caused primarily by spraying over a surface that’s contaminated with oil, grease, silicone, or wax (Note; the mold release agent on a new fiberglass body is a really common culprit.), but can also be caused by using thinner or reducer in place of a wax and grease remover during your pre-paint preparation. Though not as common but still an occasional cause may also be painting over an existing finish where an additive like Smoothie (a fisheye preventer) has been used. If you end up with a fisheyes there are a few ways to address the problem. First, you could let the area dry and then sand it to a smooth surface (below the fisheye craters) and respray the area. Or, if they show up in a basecoat you can let the coat flash-off and follow it with a real light mist coat to try and seal and bridge the fisheyes. Or, you could, as a last resort, stop what you’re doing and remove the wet paint film with solvent and then clean and refinish the area. Preventing fisheyes from forming in the first place is by far the best bet. This can be accomplished by proper prep work and making sure you have a good air filtering system that’ll prevent oil and moisture contamination.
Wrinkling, often called lifting, is when an existing paint layer shrivels during the application of a new finish or as the new finish dries. This is caused by the solvents in the new finish attacking the old finish. You’ll most likely see this malady when recoating enamels or urethanes that are not fully cured or if and when you exceed the maximum flash (dry) or recoat time during application. It’ll also sometimes happen when you recoat a basecoat/clearcoat finish where the old clearcoat had an insufficient film build. In this situation you’ll have to strip and refinish. This circumstance can be prevented by not exceeding a products maximum recoat time during or after application, by not shooting lacquer over enamel or urethane, or avoiding spraying under or top coats excessively wet.
Air trapping causes small craters that are similar in appearance to fisheyes. These are caused by tiny air bubbles trapped in the fresh paint film that rise to the surface and “pop” causing small crater-like depressions. These “craters” are usually caused by under atomization of the paint due to either too low of an air pressure setting, improper spray gun adjustment, spraying with your gun too close to the surface, or moving your gun too slowly across a panel. Depending on its severity, cratering can repaired by either sanding with 1200-grit or finer paper and then polishing to restore gloss, or by sanding and respraying the area. You can avoid this problem by maintaining correct spray gun speed and distance, making sure you’ve got the right cap/nozzle/needle setup for the type of product you’re spraying, and making sure you’re using the correct recommended air pressure.
In this particular case bleeding isn’t something you’d grab a bandage for—bleeding in this situation is when you end up with a discoloration in your topcoat color (most commonly a red or yellow stain) when painting over an existing finish. This is because the solvent in the fresh topcoat sometimes dissolves soluble pigments in the old finish allowing them to seep upward into the fresh paint thus discoloring it. You’ll also sometimes see this when red crème hardener used in body filler bleeds up through a light color. You can sometimes repair a situation like this by letting the stained topcoat fully cure and then spraying a two-component sealer over it followed by a fresh coat of color. If you think you may encounter a possible bleeding situation your best bet would be to use a good sealer before topcoating, or in the case of body filler under a light topcoat using white crème hardener instead of red or blue.