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Autobody Paint and Wet-Sanding Tips From the Pros

We’ve shown you the sweat and the prep—now to laying down the finish

Jim Smart Mar 28, 2019
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In an earlier installment, we took you through the grind of tedious preparation for a show-caliber paintjob at A.R. Auto Body in Lancaster, California. The true test of great paint is methodical preparation—getting a perfect surface on which to lay paint. When heading down the home stretch, you want a surface long on good paint flow and adhesion. With Axalta Cromax, you want to go directly from primer/sealer to paint within the time span called for by Axalta. It is all about chemistry and compatibility where basecoat finishes mate well with topcoats.

The body pros at A.R. Auto Body taught us about the importance of final surface prep with a good wet-sanding of the foundation with 400-800–grit paper; we got ours from Summit Racing Equipment. The most revealing form of body prep is the block and board sanding along with the guidecoat that catches even the smallest imperfections that can show up in the final finish. The greatest challenge is sticking with body prep until all the imperfections are gone. At times, you feel like these pesky imperfections will never be gone. It takes tremendous patience and tenacity to get great paint because if you miss anything, you’re stuck with it when the paint cures.

We’ve covered all of the toughest body prep challenges and have achieved a perfect surface. It is now time to lay down primer/sealer, allow it time to cure, and wet-sand the surface to make it suitable for good paint adhesion and flow. We’ve explained to you how important it is to use paint products that are compatible, which is why we’ve used Axalta products throughout. CHP

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The devil is in the details during body prep, which includes eliminating all debris that might contaminate the sealer, basecoat, and/or clearcoat. A.R. Auto Body goes over inner body structures with a tack cloth and compressed air to remove all debris. Another option is to use a pressure washer, which gets into the tight spots easily missed with compressed air. If you use a pressure washer, allow plenty of time for drying.

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A pristine paintjob is about chemistry and getting the paint mixed properly before it goes into the pot. Follow Axalta’s instructions to the letter for best results. You’ll want a good water and dust separator in the air line. Empty the separator frequently. Always wear a quality paint respirator mask whenever working with paint or clearcoat.

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The basecoat begins with doorjambs and inner body structures, which should never be done last. Jambing comes first because you don’t want overspray on exterior surfaces that have already been painted.

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Close attention to detail is crucial when you are jambing because it’s so easy to miss important locations you’re going to see getting in and out of the car.

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The Axalta Cromax basecoat has been applied to all the jambs and is allowed to cure. This is the color coat. It takes on a whole different perspective when we apply the clearcoat.

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With jambing out of the way, we’re ready to lay down color. Two deep coats of Axalta Cromax basecoat are applied and allowed to cure. It is wise to allow the basecoat a couple of hours to cure before applying the clearcoat.

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When the basecoat cures it is actually disappointing because it is so dull. However, it is dull for good clearcoat adhesion. You want the topcoat to creep into the surfaces of the basecoat and blend into a single coat.

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With the basecoat cured and ready for the topcoat, methodical policing of dust and debris is next. A tack rag is used along with compressed air to chase off any dust, which will show up in the clearcoat. Small particles of dust can be color-sanded and buffed out.

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Axalta Cromax clear is applied beginning on top as shown. The paint gun is held steady and follows a path from leading edge to trailing edge, terminating spraying at each end. This ensures a smooth, even coat from end to end. The clear is allowed to cure, with one or two more coats to follow. You want a thick enough coat of clear to where you can color-sand and buff with enough room on top.

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Once the roof is complete we move next to the hood and decklid, then each broad side of the body. Paint is applied top to bottom to allow overspray to fall where we’re going to paint next. The overspray then blends into the clearcoat.

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Painting is complete. This is the hood where we’re going to map out rally stripes and apply them in a separate story in Chevy High Performance. The hood and nose panel have been wet-sanded with 800- and 1,000-grit paper.

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The decklid and filler panel have been scuffed to achieve good paint adhesion when the rally stripes are applied. When you examine the finish this way, it is hard to imagine it with a shine.

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To get a show luster finish, the clearcoat is first wet-sanded with 1,000- to 2,000-grit paper, which yields exactly the opposite finish you would expect. This cuts the clearcoat, making it dull, getting it ready for buffing. It also gets the surface truly flat to eliminate any irregularities. This step is crucial, especially with darker colors.

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When we’re color-sanding the clearcoat, extra care is taken not to touch the corners and edges, which can wear through the clear and basecoat all the way down to the primer.

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This is exactly the look you will get from color-sanding, which is the clearcoat in suspension. The surface is washed thoroughly and allowed to dry before the buffing process begins.

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With color-sanding out of the way, we’re ready for the final buffing process. The first lesson in buffing is to never buff edges or crowns in the metal. A.R. Auto Body begins the buffing process with water and 3M compound for that initial buff.

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Do you see the difference? When you examine the color-sanded surfaces and compare them with the first wet buff cut you can see the richness of the blue metallic come out.

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When we put the wool buffing pad to work with 3M compound and careful modulation you can watch the luster come alive. Stay away from edges and crowns, which are easily burned down to the primer and metal if you are not careful.

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The buffing wheel glides across the surface with mild pressure from end to end until the clearcoat exhibits depth. You can see the difference from the right side to the left.

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You can see the difference between the wet buff and the dry buff here. The left side is finished and ready for final washing with detergent and water. If you’re seeking a factory finish, you’re going to want orange peel in the finish, which means no color-sanding or buffing. In fact, you’re going to want a single-stage urethane paint because the automakers didn’t do two- and three-stage finishes back in the day.

Photography by Jim Smart

Sources

Summit Racing
800-230-3030
www.summitracing.com
Axalta
855-547-1461
axaltacs.com

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