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How to Prepare a Car for Fresh Paint

Prep School: Preparatory Work Leads to an Ivy League Paintjob

Gerry Burger Mar 20, 2018
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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


1. The day you roll your Corvette into the spray booth is a true milestone. All those hours of work are finally going to pay off with a laser straight body. But let’s back up a bit and see what goes into a professional final pre-paint prep.


2. At this point, our ’68 Corvette has had any structural repairs, stress cracks and wavy panels repaired and we have a basically straight body with the resulting work scratches. It’s in the booth, taped-off and ready for final primer.


3. Here it is in final primer. The two-part, high-fill PPG epoxy primer will provide the final finish and does an amazing job of filling work scratches and other minor imperfections.


4. A lot goes into pre-paint preparation. You’ll need several grits of sandpaper ranging from 40 to 400, sanding blocks, oribital sander, tape, fillers and the list goes on. We found the simple way to get it all in one big box was to simply order Summit Racing’s Paint Prep Combos.


5. A light guidecoat was sprayed over our epoxy primer. Because of the high-fill capacity of the primer, it hardens with an orange peel finish, but it also has enough fill capacity to hide work scratches and other minor defects.


6. Part of the Paint Prep Combo was this assortment of high quality sandpaper and sanding discs. This is all “dry” sandpaper, not shown it the assortment of 220-, 320-, and 400-grit “wet” sandpaper designed to be sanded with water.


7. A dual action sander like this one manufactured by Ingersoll Rand was purchased from Summit Racing. This orbital sander will speed up the sanding process, but remember to keep the sander in constant motion and don’t use excessive pressure on the primer surface.


8. Sanding is a time consuming process. Here, the decklid and part of the quarter-panel is sanded to 320-grit. Unfortunately, there is no method to speed up quality bodywork. As the saying goes, “We have fast and we have good. We don’t have fast and good.”


9. The dual action sander is working on the quarter-panel. A 320-grit sanding disc is used, and it is clear to see the surface needs a good cut to smooth the surface.


10. This a close-up look at the decklid showing the difference between the orange peel surface in the dark gray guidecoat and the perfectly smooth surface after sanding.


11. During the sanding process you will discover some deep scratches and minor low areas that may require actual filler. For the smaller scratches we used creamy filler known as USC Icing; for bigger imperfections use USC Kromate Light filler.


12. One small area in front of the rear tire required a bit of filler and a second topcoat of primer. Before priming we used a wheel cover (also from Summit Racing) to cover the wheel placed by San Rosic. The cover protects the wheel and tire, and also prevents dust and dirt from around the wheel from being blown into our primer.


13. After the entire body has been sanded with 320-grit sandpaper, Rosic wipes the car down with Summit Surface Wash to eliminate sanding dust and residue.


14. With all the panels clean, we applied a coat of 3M dry guidecoat to the panels. This product goes on with an applicator and gives a uniform guidecoat that will be sanded off with 400-grit wet paper.


15. The quarter-panel has now been covered with the 3M guidecoat. As you sand this coating off keep a keen eye for even minor imperfections. If an imperfection shows a little bit in the primer, it will look even worse in the finished paint.


16. Part of our Summit Paint Prep Combo kits included these Dura-Block soft sanding blocks. These blocks work great as they will conform to curves but still produce a perfectly flat, sanded surface. You can use the blocks for wet or dry sanding.


17. Rosic begins by wet-sanding the quarter-panel with a flexible block and 400-grit wet sandpaper. A sponge is used to wipe the sanding water off the panel. The water will provide a temporary shine to the panel. By viewing the panel on an angle, this shine will help you detect any area that is not perfectly straight.


18. Fast forward a couple of days and our body is fully sanded and ready for final cleaning and new masking tape and paper. The existing paper and tape is coated with primer and sanding residue that would blow off into our final paint.


19. Hot Rods by Dean uses paint masking paper from Summit Racing. The quality paper is heavy enough to resist soak through of a normal paintjob and strong enough that it doesn’t rip. The Summit Racing paper rack makes cutting the paper quick and easy.


20. Rosic tapes the car for final paint; it’s a time consuming task. It is one of the most important parts of any paintjob and meticulous fit of the tape is important. Care is taken to cover the window and chrome while ensuring there is no primered surface under the tape.


21. Taping the windows can be tricky. First, the window weatherstripping is taped off. Then masking paper is cut to fit the glass area by Rosic and the paper is slipped down inside the door.


22. Note the paper is down an inch or so inside the door. Then the final piece of tape holds the paper in place. This keeps the paint off the trim and glass and also prevents any dirt from blowing out of the door.


23. After the car is completely masked off the surface was wiped down with Summit Racing Wax and Grease Remover to eliminate any trace of sanding residue and oils that may have transferred from hands during the masking process. Next, the final wipe down is done with a tack rag that is gently wiped across the surface to remove fine particles.


24. The professionals at Hot Rods by Dean prefer to work with precision spray guns like this DeVilbiss Finish Line gun. A high-quality gun is particularly important when spraying metallic paint. The gun was sourced through Summit Racing.


25. Modern epoxy primers and urethane topcoats are toxic. It is extremely important that you avoid contact with your skin and lungs. This Crew Coverall and high-quality respirator from Summit Racing will provide the required protection.


26. Back in the lacquer days you could mix paint “by eye,” but those days are over. Modern PPG paints must be mixed precisely for proper flow and curing. Part of the Summit Paint Prep Tool Combo includes paint sticks, gloves, filter funnels and mixing paint pails.


27. Pieces such as headlight housings, T-tops and other removable pieces were painted separately to ensure proper paint coverage.


28. As you can see, the panels have multiple recesses and contours so painting them off the car is the only way to achieve complete coverage.


29. The final masking is done in the paint booth using materials from the Summit Racing Paint Prep Cleaning and Masking Combo. The Norton Paint Check plastic is specifically designed for automotive paint. This plastic sheet was used as an apron from the bottom of the car to the floor to prevent dirt and dust from being blown out from under the chassis during the final spraying process.


30. Before applying the final color PPG sealer was sprayed over the entire body and allowed to cure in the booth. Sealer aids in paint adhesion and keeps bodywork stable.


31. We were so pleased with the incredible PPG paintjob from Hot Rods by Dean we just had to include a photo of the final finish. The color is ’68 Corvette only, Code 22969 Corvette Bronze Poly. We used all PPG products from primer to the finished paint. Keeping it “all in the family” ensures compatibility and good results. If you think it looks good here, just wait until it is color-sanded and buffed!

Photos by Brian Brennan


Summit Racing
Akron, OH
Hot Rods By Dean
Phoenix, AZ 85027



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