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How to Blend Bumper Paint on a C5 Corvette

How to blend in a bumper paint repair

Jim Smart Dec 28, 2018
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Few things yield a higher pucker factor than paint damage, then having the damage repaired only to discover the repair doesn’t match. Even from 30 feet away a poor paint match is obvious, especially with a metallic finish. It makes you want to clobber the creep who backed into your bumper cover. Late-model Corvettes have long been factory-fitted with urethane bumper covers, which hide the bumpers and structure beneath. Minor bumps are easily repaired, but when you have the bumper cover repaired or replaced, getting a perfect paint match can be hit or miss.

We’re working with Jack Grubisich, known to Corvette buffs as “McJack” of McJack’s Corvettes in Santa Ana, California. Jack performs dozens of restorations, repairs, and repaints each year. He understands how to work a fiberglass body and flexible urethane panels to where repairs defy detection. He works and perfects the surfaces, then gets the paint mix just right to where the paint blend cures and matches perfectly. And, when you can do this with some of the toughest metallic colors imaginable that’s saying something.

One of Jack’s customers brought him a C5 Vette that had been bumped in a parking lot and then repaired by a body shop that couldn’t get a proper paint match. You could see the difference between the quarter-panels and the urethane rear bumper cover. Jack wet-scuffed the quarter-panels and bumper cover perimeter with 1,000-grit 3M paper from Summit Racing Equipment for good paint adhesion. To achieve a perfect blend between the quarter-panels and bumper cover Jack masked the bumper cover’s fascia (where the taillights and license plate are) to where the repaint covered the perimeter, yet it did not involve the area around the taillights. The break happens where the perimeter meets the fascia to where the color difference is impossible to detect.

Jack is using a Sherwin-Williams urethane basecoat/clearcoat finish, which he has custom mixed to match the existing color. And, if there are any irregularities in color, Jack does some of his own custom mixing to get the final finish spot on. He understands what the color looks like wet and what it will look like cured, adjusting his mixing process accordingly.

Jack likes to stick with original factory-style finishes on classic C1, C2 and C3 Corvettes, which means a hint of orange peel, just like the St. Louis assembly plant did with lacquer a half-century ago. C4 and newer Corvettes get a more traditional two-stage basecoat/clearcoat finish that is more in line with how they’ve been painted since 1984 and the transition to the new state-of-the-art Bowling Green, Kentucky, assembly plant.

We’re going to follow along with Jack as he tackles a challenging C5 paint match in silver. Although Jack is using Sherwin-Williams finishes on this C5 project, he has experience with PPG and Axalta finishes, as well. He understands the idiosyncrasies of each manufacturer, the types of solvent and waterborne finishes each has available, and how to apply them. Vette

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While replacing the bumper cover, the body shop didn’t get a good color match on this C5, which is a challenge for any body shop, especially with metallic finishes. The owner wanted a perfect match, which was why he came to McJack’s Corvettes, which has an excellent reputation for color match.

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Jack begins his color match routine with a 1,000-grit wet-sanding with 3M paper. He lightly block-sands the surface to be painted as shown until he achieves a dull matte finish. The trick is to not sand so hard that you go down to the primer coat.

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You should have a matte finish like this once all block-sanding with 1,000-grit paper is complete.

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Jack masks all of the areas where he doesn’t want paint overspray using no-creep professional masking tape. He applies finger pressure to the tape edge to eliminate any chance of paint creeping beneath the tape and paper mask.

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Jack uses the palm of his hands along with compressed air to remove any debris that could contaminate the repaint. It is also good to use a tack rag for this purpose. Use a high-evap’ spray solvent to clean seams and crevices, then blast these areas with compressed air. Closely examine the surface for any dust and dirt using both your eyes and fingertips.

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Jack begins the repaint with basecoat color with even spraying from end-to-end. He squeezes the trigger at the beginning of each pass and stops at the end to prevent unnecessary paint accumulation.

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Note how carefully Jack has masked all areas he does not wish to repaint. He masks items like tires and wheels to prevent any overspray from getting into unwanted places.

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Jack uses a pinstriping brush to apply paint to gaps and seams. He then wipes the surface to where brush-applied paint is only in the gaps and seams. This basecoat paint has not cured, which is why it is lighter in color.

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Jack has applied the silver basecoat. He is using the paint gun to apply compressed air to the surface to eliminate any debris before actually squeezing the trigger and applying the clearcoat.

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Laying down clearcoat requires an abundance of caution because this is the shiny topcoat everyone is going to see. Again, squeeze the trigger at the beginning of each pass and stop at the end. Make each pass smooth and consistent from end-to-end. Never pause the pass with the trigger squeezed.

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Jack is blending the color basecoat here between the quarter-panel and bumper cover. Although this looks lighter than the existing color it has not cured yet. By the time it cures you will never be able to see the difference.

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The surfaces have been wiped down with a tack rag and blasted with compressed air. Jack is applying the clear topcoat as shown here. That first coat of clear should be light and allowed to cure. This is your base adhesion coat that attaches the clear to the color.

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When Jack lays down the second and third coats of clearcoat he lays them down wet, which allows good flow and an even surface. He suggests three coats of clear to give you plenty of room for color-sanding and the rubout. If you are seeking a factory finish, skip the color-sand and rubout.

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Check this out. Jack is applying the second and third topcoats. This finish almost doesn’t need color-sanding and a rubout.

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The Corvette factory in Kentucky never color-sands and rubs out the final finish. These coats of clear get it like the factory. For a show finish opt for color-sanding and a rubout.

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Can you see the difference? The quarter-panel and bumper cover blend nicely. Were there a difference, it wouldn’t be noticeable because the new paint ends at the trailing edges of the bumper cover. This image was taken in a paint booth under artificial light. Outside in the sun, this silver metallic finish blends perfectly.

Photography by Jim Smart

Sources

Summit Racing
800-230-3030
www.summitracing.com
Sherwin Williams Co.
Cleveland, OH 44115
McJacks Corvettes
714-775-2799
www.mcjackscorvettes.com

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