Like most things in life, creating a great paintjob involves hard work, education and experience. And like virtually everything in our universe, bodywork materials, tools and products are in a constant state of flux, ever-changing to provide a superior final finish. While this story may be prep school for some of our readers, others may consider it more of a continuing education course.
The subject of this paint prep course is our ’68 Corvette project. For readers who missed earlier project installments, this car had been sitting in a dry garage in Arizona for better than 32 years, yet another project car tucked away in the corner. Of course, being a lifelong Arizona car means the chassis and all steel components are rust free, and since the car has spent better than half of its life parked indoors, the usual sun damage one might expect from a sunbelt car has been avoided. Another bonus was most of the car had the original paint sanded off with just a couple coats of old lacquer primer on the main body, so stripping the car to bare fiberglass was done with a combination of power orbital and hand sanding. That situation has made the bodywork on this car very straightforward when compared to a car that has been outdoors for 50 years.
But even the very best vintage Corvette brings with it challenges that are different from a steel car. First, the very texture of fiberglass can cause problems and then there is the matter of the bonding seams where epoxy bonding agent is used to adhere two fiberglass panels together. Because joint epoxy is a different material than the actual fiberglass, problems can arise in the finished paint, particularly in the sun as the epoxy seams and fiberglass seem to have different expansion rates. If the body is not properly prepared it is not uncommon to have dreaded “ghost lines” at the panel seams. Even GM had similar problems when these cars were new, but they were working with lacquer based paints, which pale in comparison to the modern PPG high-fill epoxy primers and urethane topcoats we are using.
Using modern epoxy primers, high-quality body filler and allowing proper time and temperature for curing will go a long way toward preventing such problems. We are also big believers in using the same brand of paint products from primer to topcoat. We prefer PPG products and used their products exclusively from primer to the final clearcoat. One thing is certain, rushing through paint and bodywork is only a shortcut to problems. It is imperative to follow instructions and be exact with the proper mixing ratios of all products. Catalysts, hardeners and thinners all play an important role in making each product perform properly. Drying times and even the proper temperature range for each application is also important. Rather than rushing, allowing a little extra cure time will pay off in the long run.
Happily, our Corvette body was in above average condition so the bodywork was not that difficult (easy for us to say, since we didn’t actually do the work). All of our work was performed by Sean Rosic, one of the professionals at Hot Rods by Dean (Phoenix, Arizona). If you have experience with painting cars and parts you can lay down a great paintjob at home. As a matter of fact, doing your own bodywork has been simplified thanks to companies like Summit Racing as they can supply you with body repair materials that take you from bare fiberglass to finish product, including all the tools to do the job right. If you are doing a complete bodywork and paintjob on a car, looking at Summit Racing’s “Paint Prep Combos” will provide you with the tools and material groupings that include the things needed for each step in the process.
We left the most important information to last. Safety. While modern paint and bodywork materials are fabulous for the body of your car, the same cannot be said for the body of the man applying these products. Catalyzed paint products and sanding dust are toxic, making the use of a high-quality respirator and protective clothing important. A full body paint suit, gloves and proper respirator is imperative when spraying catalyzed paint. The good news is Summit can handle the safety gear, too, and wearing a new pair of paint coveralls also minimizes unwanted dirt and dust in that final paintjob.
Every step of bodywork is important, from filling cracks and holes with fiberglass cloth and resin to fixing wavy panels with quality filler and sanding the primer for the final finish. Our story is about the final prep stages. The major repairs have been completed, the filler shaped with 40-grit, followed by 80-grit and 150-grit before priming the surface with a high-fill, two-part PPG epoxy primer. We are now in the final stages, finding all of those little flaws, scratches and occasional low spots that must be corrected for a flawless finish.
We begin by spraying a light, black guidecoat over the body and sanding it with an orbital sander with a soft pad and 320-grit sanding pad. Epoxy primers leave a textured “orange peel” surface due to their high-fill content. This first sanding will cut that down quite quickly with the guidecoat providing a visual guide. After the surface is cut it is rinsed and wiped clean with Summit Surface Wash. Any deep scratches we found along with one or two very minor low spots were filled with USC Icing. Icing is a creamy body filler designed just for filling deep scratches and minor low areas. If you discover a dramatically low area it is best to use USC Kromate Light body filler as it is designed for thicker applications. One side note, yet another great feature of the modern epoxy primers is the fact they are designed to have the body filler applied over the primer with perfect adhesion, something that didn’t work well with the ancient lacquer based primers.
After filling a few work scratches with USC Icing and cutting it down to 320-grit we spot-primed over the areas where the filler had been applied and then cut the primer to 320-grit.
With the body perfectly clean, we applied a coat of 3M dry guidecoat to the entire body (also available from Summit Racing). This dry guidecoat uses an applicator to apply a uniform guidecoat over the panel, providing a great visual aid to finish the panel. Armed with several different shapes and sizes of soft sanding blocks and 400-grit paper, we wet-sanded the body until every bit of the guidecoat was gone. This left us with a perfectly prepared surface, ready for our final paint color.
We removed all of the masking tape and paper from the car as it was covered with primer and sanding dust. Final cleaning of the paint surface was next. As you wipe down the panels with Summit Surface Wash, followed by Summit Wax and Grease Remover, look carefully at the panels for any defects, scratches or wavy panels. Viewing the primer on different angles when it is wet is a great way to detect minor problems that may require more sanding or even filler. Remember, as painful as it may be, if you discover a problem, go back and repair it properly now, because that little problem will be magnified by the final finish. Once the car is clean, blow-dry the body, paying special attention to areas that may hold dirt, dust and water. Wipe away any sanding residue that comes out of the cracks and crevices on the car with Wax and Grease Remover.
Now you are ready to tape off the car in preparation for the final finish. Use high-quality 3M masking tape designed specifically for bodywork. Do not use general grade masking tape. Also, it pays to buy plastic paint cover material for large areas like the engine bay along with a roll of bodywork masking paper. This paper is strong and thick enough to cover windows and other openings and prevent overspray and paint absorption. Here’s a news flash, the days of using newspaper to tape off a car are over, the paper is too thin, the print can transfer to car parts when it comes in contact with paint and it has no real strength. Using the proper masking materials is an investment in a great finish.
Careful masking is imperative for a good paintjob so take your time, be certain to have good lighting and when the masking process is complete wipe the car down one last time with Wax and Grease Remover to eliminate any potential body oils from your hands touching the car during the masking process, followed by blowing the body with air to remove any lint or dust. The final step is a light wipedown with a tack rag. These packaged rags are sticky and designed to pick up lint, dust and small particles. When using a tack rag, do not push down hard as you can transfer the sticky substance to the surface.
Once you are assured the body is perfectly clean and dry it is time to start mixing paint and laying down that perfect paintjob. The use of a high-volume, low-pressure paint gun will go a long way to using less material and cutting down on the amount of overspray. Buying a quality spray gun is a good investment for any shop, and while there are cheapo guns out there, buying a quality gun from a longtime spray gun manufacturer like DeVilbiss is best for that perfect topcoat, particularly if you are spraying metallic.
And that completes our course in Prep School with special thanks to the guys at Hot Rods by Dean, PPG, and Summit Racing for sharing these tips. Hopefully, upon graduation you will have a Corvette that’s straight, shiny, and better looking than the day it rolled off the assembly line. Vette
Photos by Brian Brennan