All of us have attempted our own paintjob with differing results from good to not-so good. But we are all aware that this is one area that’s fraught with the potential for things to go wrong—sometimes terribly wrong. Problems occurring with the paintjobs are so common to those of us in the hot rod world it almost seems natural or normal to have a problem here and there. It shouldn’t be and the more preparation that’s applied, the more knowledge of what it is you are attempting, and the understanding of the materials you are using will go a long way to minimizing these paint woes.
Just in case, we joined forces with Axalta (formerly DuPont) and came up with a number of identifiable problems that occur in our world. We have also asked illustrator and frustrated painter of hot rods (like the rest of us) Jeff Norwell to put his ink to paper and illustrate a handful of these problems. For solutions to these problems Axalta gives us the answers we will need.
Axalta provided information on 29 of the most common paint defects (and I believe I have managed 12 of them on one panel thereby banning me from the paint booth). What we have done in this article is to identify the more common mistakes, and asked our hot rod artist in residence to illustrate so that we would be able to show examples and then offer the Axalta solutions.
Adhesion Loss, Clearcoat
We’ve all seen the clearcoat that peels off from the base color. This can be the result of excessive thickness of the basecoat (yes, basecoat), the intermediate and final flash times of the basecoat are too short, wrong mixing ratio for clearcoat and its activator.
So how do we prevent this from happening? Make sure to check and recheck the correct flash times of the basecoat before applying clearcoat, make sure that all layers of paint material (base color and clearcoat) area are applied at the prescribed thickness, and make sure to mix clearcoat correctly.
But what happens if one of us hasn’t followed the instructions correctly? How do we fix the problem once it has occurred? Take the affected area and sand, making sure to isolate this area from unaffected areas and refinish.
Sometimes referred to as bleed through, staining, and stains; yes, we’ve all seen this no matter what it’s called. It will appear in the form of the original finish color or peroxide hardener from polyester body filler seeping through the topcoat, causing a discoloration of the new finish.
This can be the result of a reaction of color pigments from the original finish with solvents of the coat, which has been applied on top of it. It can be a contamination; usually in the form of soluble dyes or pigments on the older finish before it was repainted. (Many of us have seen this with cars originally painted red and then repainted over the older shades of red.) Another reason for this bleeding to happen can be the result of the old finish not well sealed or too much hardener in the polyester putty or filler was used, or the polyester putty or filler wasn’t mixed properly.
So how do I stop this from happening from the get-go? You will need to apply a sealer if there is any doubt that the bleeding will occur. You can test a small area of the old finish by applying a coat of the final color. Follow the directions on the amount of quantity of hardener when mixing the polyester putty or filler. Carefully check quantity of hardener; you can do this mixing by weight or use a dispensing machine (probably will have to have access to a professional shop for this one). Once putties and fillers are combined make sure to mix thoroughly.
Should bleeding have already occurred you will need to remove the polyester and redo the repair. Begin by sanding and then isolate the original finish with sealer and reapply the topcoat.
Sometimes known as moisture blisters, blisters, bubbling, blowing, or bubbles, this hiccup will manifest itself as bubbles or pimples appearing in the topcoat. It is generally the result of leftover sanding water in the corners, edges, crevices, or below any other art on the final paint. It can also result from the ambient humidity too high. And what none of us wants to hear but we know happens, improper surface cleaning and preparation—poor location or prep of the work area such as contamination of compressed air lines; oil, water, or dirt in lines. It’s the direct result of tiny specs of dirt left on the surface and these dirt particles act like a sponge and retain moisture. This happens when wet sanding polyester and applying topcoat without enough time for the water to evaporate. Also, insufficient drying time between coats or too heavy application of the undercoats may trap solvents, which escape later and blister the color coat. This can also occur in unison with excessive film thickness; we are in a rush and don’t allow sufficient drying time and apply too much material. When the finish is exposed to the sun (or abrupt changes in atmospheric pressure), moisture expands and pressure builds up. If the pressure is great enough, blisters form. It can also occur because the wrong thinner or reducer was used; incompatibility of materials. Use a fast-dry thinner or reducer, especially when the material is sprayed too dry or at an excessive pressure. Air or moisture can be trapped in the film.
So, how does one go about preventing this from happening in the first place? Remove any and all trim (you are removing hiding places for moisture). Make sure to use sufficient air pressure that is properly filtered to remove dirt and moisture from the air lines. Make sure to thoroughly clean the area (location) where the painting is to occur before starting the sanding process. Make sure the surface is completely dry before applying any materials (undercoat or topcoat). And, for the 100th time, never touch a surface to be painted with your hands as the oils in your skin will contaminate the surface. Make sure to match thinner or reducer to suit your “weather” conditions in area where painting will occur. Be sure to provide for amply (proper) drying time for undercoat and topcoat, making sure to allow each coat to flash properly before continuing. Always start with thoroughly cleaned and maintained equipment, such as drain and clean air pressure regulator to remove any trapped moisture and/or dirt. (It’s a good idea to drain the air tank often but especially before attempting any paint project.) Make sure surface to be painted is cleaned carefully and thoroughly.
If blistering has already occurred and the time has come to fix it, what are my options? If the blistering is severe enough the paint will need to be removed down to at least the undercoat (primer) or even bare metal. This is determined by the depth of the blisters. Next, begin the refinish process, this time not taking any shortcuts and making sure to adhere to the proper directions and techniques.