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Bring back the shine with color sanding and rubout

How to get luster back with color sanding and rubout

Jim Smart Mar 8, 2019
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Paint that has lost its luster is an age-old problem with any car … but Corvettes require a bit more attention. What do you do with paint that has gone dull? You look into the finish and cannot see your face anymore. Or perhaps you have a fresh paintjob that doesn’t have the sizzle desired. At first glance, faded, oxidized paint looks hopeless and will never come back. You start calling body shops in an effort to get an estimate for a paintjob. Sticker shock at the price of bodywork and paint these days is plenty discouraging because both paint and labor have become very expensive. Before spending your hard-earned dollars on bodywork and paint, what can you do to salvage the existing finish to where you can put off this expense for a few more years?

Through the years we’ve seen seemingly hopeless faded paint come back to a high luster with a simple color sanding and buffing. Jack Grubisich of McJack’s Corvettes tells us never to give up on paint unless there’s a real reason to give up, such as cracking and peeling. Jack tells us there’s always a certain amount of life left in paint depending upon how damaged the finish is. We’re working with two classic Corvettes in need of a color sanding and a rubout. Both have been painted recently yet they lack the luster they could have with a color sanding and buff. This process can be applied to faded paint as well. Jack’s going to show you how to bring a lackluster finish back from the dead.

“I begin the cut-and-buff process by dry sanding with 1,000-grit with a dual-action sander and 3M paper,” Jack tells us, “I do this first for two reasons. First, it’s environmentally sound because there’s no water and paint runoff, which goes into the water supply.” He adds, “What’s more, it cuts the surface faster, getting me to the next grit level, which is 1,200-grit 3M paper.” He goes on to say, “Then, I sand by hand with a 3M hard-rubber sanding pad with a nice even back and forth motion and a small amount of water dripping from a clean wet rag on the area being hand sanded (not a running hose like we used to do in the good old days) to get a smooth, even orange peel-free surface.”

Jack continues, “Then, I go over the entire body again with 1,500-grit 3M to make the buffing faster and easier. It is also a good time to double-check the surface for any issues before I continue. Then I start buffing.” Jack brings home another point, “When I am dealing with a factory finish, I only hand sand with 1,000-grit and water with a sanding pad. This way, you get the factory orange peel.” Jack comments, “A good painter not only matches the color but also the orange peel and even the size of the orange peel, which is accomplished by how much you thin the paint.”

Why Does Paint Fade

To understand why paint fades you must first understand what paint does. Paint provides a protective coating over the fiberglass, die-cast parts and steel. It also provides all-important aesthetics. It has to look sharp. There are two basic approaches to automotive paint: single stage and multi-stage. Single stage paint is the application of one type of paint in multiple coats and you’re finished, which is the way cars were painted back in the day. Multi-stage paint consists of a color basecoat with a clear topcoat, which is nothing new by the way. In hot rod building in the old days we’d lay down a color coat in enamel or lacquer, then, pour on a topcoat that could be color-sanded and buffed to a high luster. We called it “show car” paint. Today, it’s common to work with polyurethane paint with a flat color basecoat, then, clearcoat on top like the old days. And, when you color sand and buff the clearcoat the result is stunning.

Paint fades because it takes a terrible beating over time. It’s exposed to the sun, wind and destructive ozone. This is especially true in the south from Florida to California. Paint has to endure a wicked slipstream that comes with speed, bug splatters, debris, sand, a stray stone and more. All things considered, paint holds up pretty well overtime considering the beating it takes.

Factory paint isn’t as thick as it was 50 years ago. General Motors used lacquer where Ford, Chrysler and American Motors used enamel. GM used lacquer because it was easier to repair at the factory and dealer than enamel. Factory finishes and repaints were four-to-six mills thick in those days compared to the hair-thin one-mill basecoat and 1.50-to 2.00-mill thickness you have today. This means it can get risky if you color sand and buff the factory clearcoat today. You could run into the basecoat and primer. Paint consists of four basic elements: pigment, which gives us color; binder, which holds the pigment together; solvent, which allows the pigment to flow during application and additives crucial to its success. The additive can be literally dozens of different elements that enhance paint value, including those that make the paint tougher and less prone to failure.

Now that you know what paint is, how do you understand what happens to it over time? If you look at paint magnified you can see the makeup of the finish, which is rather crude. In fact, it’s hard to believe it’s shiny when you look at it under magnification. The paint’s polymer (binder elements) consists of straight or linear molecules to complex molecules to a mix of both. Polyurethane finishes, like those used on new cars and trucks today, have a very high molecular weight without getting too into specifics here. Then, there’s something known as reactivity, which is the connection between the paint or clearcoat and the catalyst or additive of polyurethane paint. Paint manufacturers are always striving for better chemistry in order to achieve a better paint, which is long on endurance.

The elements, sunlight, ozone, wind, moisture and debris bring about changes in the physical properties of paint. They undermine the chemical links that hold paint together. However, as damaging as these elements are they are only part of the reason why paint fails. Paint tends to decay even in a protected environment under a car cover. In bright sun, paint decays via a process known as photo oxidation. Free radicals that age our skin also contribute to paint deterioration. If it rains or your sprinkler system leaves a bunch of moisture on the finish, water droplets intensify the photo oxidation. Think of this like taking a magnifying glass under the sun and burning a hole in a piece of paper. A water droplet does the same thing to paint by magnifying the sun’s rays. Add dust in the air to the moisture and decay happens rapidly.

Never kid yourself; just waxing the finish will not bring back the luster. You have to cut the surface with sandpaper before you can buff it out. Also keep in mind the color basecoat doesn’t make a statement by itself. When you top it with clearcoat the color comes alive because you are viewing it through the clearcoat. That said, closely examine the finish and determine what’s next. A chalky faded finish can be salvaged. It can even be said damaged and peeling clearcoat can be saved if you avoid cutting into the basecoat. And, did you know you can color sand and buff faded enamel and lacquer via the same process shown here? You just have to ascertain that you have a thick enough finish working without cutting down to the primer and steel. Sometimes, it is best to work with rubbing compound alone and see what happens. The way we see color sanding and the rubout, the worst that can happen is you will have to opt for a paintjob.

Jack and his son Tony are going to show you two approaches to color sanding and buffing. Jack will go at it dry while Tony does it wet, with both gentlemen achieving very similar results. Vette

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Jack and Tony both begin the color sanding and rubout with 1,000-grit 3M paper (not shown here). Jack does it dry with a dual-action sander. Tony will wet sand by hand with 1,500-grit and a block sander.

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Jack starts out with 1,000-grit paper dry as shown with a 6-inch orbital sander, then will go to 1500-grit. Where Jack is color sanding is fresh clearcoat. Closer to the camera is uncut fresh clearcoat. He would treat faded paint the same way.

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Jack continues to cut the clearcoat with 1,000-grit, then 1,500-grit, until he has a uniform finish of dullness.

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Jack stresses a good uniform sanding without breaking through the clearcoat. Tight areas get carefully hand sanded.

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Note the difference between undisturbed clearcoat and the area being dry sanded.

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Jack carefully works the doors, fenders and quarter-panels with the sander making sure he doesn’t penetrate the clearcoat. The objective is to score the clearcoat without cutting through into the basecoat. Once you break the clearcoat it will have to be painted again.

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As Jack works his way across the door do you see the uniform swirl pattern in the clearcoat? This is what you want across the finish.

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Jack takes extra care to stay away from the edges and high spots, which can wind up down to the basecoat and primer quickly if you’re not cautious.

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Jack points out the swirl pattern that must be maintained throughout.

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Although this C2 has a nice overall shine, Jack is of the belief it needs a good cut and buff. The finish isn’t bad as a daily driver. A good color sanding and rubout takes this finish to the next level.

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Right here in this concave area is where an orbital sander can get you in trouble. Hand sand these areas and play it safe.

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Watch this C2 Corvette transform from a dull shine to dull with the 6-inch dual-action sander. Side scoops get hand sanded to prevent cutting into the edges and down to the fiberglass.

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This is what 1,500-grit paper will do to the clearcoat. It cuts the clearcoat down to a dull finish. When compound is applied to this surface the transformation will be stunning.

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Jack continues to work his way around the body. The key to success is to be uniform in your wet or dry sanding program. Again, hand sand recesses like scoops and air extractors.

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A once shiny finish becomes rather dull as Jack continues to cut the clearcoat. At first glance this is enough to get anyone in a panic. In truth, a brilliant show car luster is just a short time away when Tony applies the 3M compound and a buffing wheel.

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Note the good uniform swirl pattern across the surface. This is the look you want in the wake of 1,000- and 1,500-grit dry sanding. Wet sanding will achieve the same result.

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Tony gets after the C3 with water, a sanding block and 1,500-grit 3M paper to get a nice hand-rubbed dull that will compound and buff out nicely. He gently wet-sands the surface until he gets a uniform dull void of any shiny spots.

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The nice part about wet sanding is its hands-on nature where you have more control of how you navigate the surfaces. You can work concave and convex surfaces with greater control. The main thing is to keep water flowing.

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Tony has wet-sanded the hood, roofline and deck with 1,500-grit. He performs a wipe-down before tackling the rubout.

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When it’s time to rub out the sanded finish, McJack’s Corvettes uses 3M’s #36060 rubbing compound. This is the industry standard for taking a color sanding and rubout to its destination.

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Rubbing compound is globed on as shown and taken on a trip with a buffing wheel. Body shop professionals have different opinions on what to use. This is what Jack and Tony use at McJack’s and with stunning results.

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Tony cuts into the clearcoat using the weight of the buffer to do the work. Too much pressure and you cut into the basecoat and primer, which means you get to paint it all over again. It is so easy to burn the finish, so be careful.

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Tony gently drags the buffing wheel over our C2 Vette, running it back and forth until he is satisfied with the result. Remember, too much isn’t necessarily a good thing, meaning know when to stop.

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Look at what happens to the wet-sanded dull finish. By gently modulating the buffer back and forth you get the shine.

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Look at the result of color sanding and buffing using 3M products and a little knowhow. This is a finish that will hold up well and last for years to come.

Photography by Jim Smart

Sources

Summit Racing
800-230-3030
www.summitracing.com
McJacks Corvettes
714-775-2799
www.mcjackscorvettes.com

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