Color Sanding Process - Color Sanding To Perfection
The Paint May Be Dry, But If You Want A Show-Quality Finish Color Sanding Is A Must
From the August, 2010 issue of Chevy High Performance
By Stephen Kim
Photography by Stephen Kim
Rubbing sandpaper on high-dollar paint seems as logical as dropping a dumbbell on your foot right after it's been removed from a cast. Intentionally ruining what took months, or years, of agony and suffering to accomplish is just pure madness. As much as it may defy logic, scuffing up fresh paint during the color sanding process is the most effective way to eradicate tiny surface imperfections and achieve the proverbial smooth-as-glass finish. Like weeds in a meticulously groomed golf course, regardless of the painstaking efforts put forth by even the most experienced of body men to keep them at bay, orange peel, dust nibs, and fish eye divots are inevitable consequences of the painting process. To find out why this is the case, and how to go about correcting these flaws, we tagged along as Rodney Austin of Austin's Collision & Body Works subjected the hood of a Camaro to the color sanding treatment. Quite frankly, we were stunned as we watched Rodney transform what was already a fine-looking piece of steel into a paragon of automotive perfection.
The most expensive part of...
The most expensive part of the color sanding process is buying the right tools. A variable-speed orbital unit such as this Hutchins air sander is a must, and costs a hair under $200. It turns up to 10,000 rpm, and holds sanding discs ranging from 5-8 inches in diameter.
The premise behind color sanding...
The premise behind color sanding and wet sanding is to use a sandpaper grit that's just coarse enough to remove surface imperfections. On large flat surfaces, Rodney prefers starting with 1,000-grit sanding discs measuring 6 inches in diameter for use with the orbital sander. Next, he hits the paint with a finer 1,500-grit paper. For smaller areas that require more finesse and hand sanding, the same material is available in square sheets that can also be used to wet sand.
Looking at an overhead skylight...
Looking at an overhead skylight reflected in the Camaro hood, the orange peel is painfully obvious. This is very typical of how most paint finishes look right after they exit the booth, and production paint often looks even worse. On the typical muscle car paintjob, Rodney sprays 3-4 coats of clearcoat to ensure that it's thick enough to color-sand multiple times. Before color sanding a fresh paintjob, a car should sit about four weeks to allow sufficient time for gasses to escape from the finish. Otherwise, the paint will lose its gloss more quickly after color sanding and polishing.
The Need To Sand
Hitting the hood with 1,000-grit...
Hitting the hood with 1,000-grit sandpaper reveals several imperfections. The white ripples are high spots in the orange peel, and the goal is to skim over the surface to flatten these high spots and remove dust nibs and fish eyes. The cut itself is less than one mil deep. Paint should always be color-sanded in the shade, and never in bright sunlight.
From the moment a car enters the paint booth, all the elements are working against it. While the fans and filters in a paint booth help remove the majority of airborne impurities like dirt and dust, some particulates still evade capture. "I don't care if you have a $5,000 booth or a $500,000 booth, the nature of painting a car means that you're going to end up with some dust on it. You can clean your clothes, the floor, and everything around you as best as you can, but since the paint gun is pressurized, anything floating in the air is going to stick to the paint," Rodney explains. Even uglier and more difficult to remove than dust nibs are fish eye divots, which are also the products of surface contamination. Any oil or silicon on the car's surface will cause the paint to separate, leaving behind a crater where the paint couldn't adhere to. "If you ate a cheeseburger for lunch and didn't wash your hands, you might end up with fish eyes all over the paint. That's why I don't allow WD-40 or wax anywhere in my shop. If someone's spraying WD-40 on the other side of the shop, the grease particles can still float all the way across the room and contaminate the paint."
Fish eyes are more difficult...
Fish eyes are more difficult to remove than dust nibs. Although it's tempting to concentrate more pressure over a fish eye to sand it out, the sander must be moved across the surface continually to achieve as flat and uniform of a cut as possible.
After removing all orange...
After removing all orange peel, dust nibs, and fish eyes with 1,000-grit sandpaper, it's time to hit the paint with 1,500 grit. Unlike the first round of sanding that removed surface imperfections, the second round of sanding merely removes the scratches left behind from the previous step. Note the uniform dullness of the sanded hood.
The polishing phase is very...
The polishing phase is very similar to the sanding phase in that each successive step uses a finer cutting compound. The pink synthetic cutting cream, from Production Car Care Products, is the coarsest. The white 3M Finishing Material is used in the second step, followed by the gray bottle of 3M Final Glaze. Lastly, the yellow 3M Imperial Glaze is applied by hand.
Perhaps the most obvious paint imperfection is orange peel, which refers to an uneven finish that resembles the skin of an orange. Except for mega-buck exotics like Lamborghinis and Bentleys that are often color sanded at the factory, every production car exhibits a certain degree of orange peel. Even if preventive measures are taken during the paint process, orange peel can be minimized but not entirely eliminated. "Paint comes out of the gun in an atomized state in the form of tiny droplets. As the droplets hit the surface of the car, the gaps between them begin to fill in," says Rodney. "This leaves a ripple effect behind. Making sure that your application technique and paint gun adjustments are spot-on will only do so much. The nature of how paint is transferred from the gun to the car will result in some amount of orange peel."
When stepping up to a finer...
When stepping up to a finer cutting compound, the polishing pads must be changed as well. The pink pad is the coarsest, and the yellow pad is a hair finer. The gray foam pad is the finest, and is used to remove tiny micro scratches from the surface. Rodney's polisher of choice is a Makita variable-speed electric unit, which costs about $200.
It's always a good idea to...
It's always a good idea to tape up areas such as the driprails and any sharp edges. Since the brunt of the polisher is concentrated over a smaller surface area in these spots, even a momentary lapse in concentration can result in a burned-up edge.
It may seem like common sense,...
It may seem like common sense, but the polishing pad should be positioned to rotate into the body panel. A pad that rotates away from a panel can burn up the edge, or even chip off the paint.
The first phase of polishing...
The first phase of polishing involves using the coarsest cutting cream and polishing pad. Rodney says that a polisher or sander should never be operated at full speed. Instead, he recommends using higher speeds in long, flat sections of a panel and slower speeds around radiuses and edges. The polishing pads should be wet, but not saturated, and more polishing compound should be added when the pad won't glide over the paint as easily. Likewise, the paint should always be viewed at a low angle, as looking straight down at it will hide scratches and imperfections
After the second round of...
After the second round of polishing, most visible scratches have been removed, but the paint looks very dull. The first step in restoring the luster is applying 3M final glaze with the electric polisher and a foam pad.
The very last step involves...
The very last step involves applying 3M Imperial Hand Glaze to the paint. Much like waxing a car, it is applied and removed by hand. Unlike wax, the 3M glaze is silicon free, which allows new paint to breathe.
Sanding It Out
Color sanding is an arduous...
Color sanding is an arduous process that takes practice, skill, and loads of patience. Completing the process on half of a hood took over an hour, and Rodney says that color-sanding an entire car requires 40-60 hours. Nonetheless, the results are stunning to say the least.
Much like sanding a block of wood, removing imperfections from paint and smoothing its surface requires hitting it with a series of abrasives. Color sanding involves sanding the paint with a very fine-grit sandpaper, followed by repeating the process with an even finer-grit sandpaper. The paint is then polished in several stages using successively finer rubbing compounds. "The very first round of sanding uses 1,000-grit sandpaper, which is just coarse enough to remove the orange peel, dust nibs, and fish eyes. In each step after that, you're just removing the scratches left behind from the previous step," Rodney explains. "With a single-stage paint, you're cutting into the paint itself, and with a dual-stage paint, you're cutting into the clearcoat. The depth of the cut is less than one mil, and the goal is to cut the surface just enough to achieve a nice uniform flatness. It takes a lot of practice and patience to color-sand, and you can burn up a panel very quickly if you get it wrong, so I highly recommend practicing on an old fender or hood before trying it out on your project car."
A car can be color-sanded...
A car can be color-sanded once fully assembled, or panel by panel on a work stand. Rodney prefers working on a stand since it allows sanding tough-to-reach areas such as rocker panels more easily.
According to Rodney, one caveat...
According to Rodney, one caveat of reproduction body panels is that the heat produced from sanding and polishing can make the glue in the support tabs come loose, causing the entire panel to sink. Consequently, it's important to maintain consistent movement over the panel to help dissipate the heat.
Color sanding fiberglass is...
Color sanding fiberglass is no different than metal, and the results are the same. Objects reflected off of this mid-year Vette look crisp and well defined.
For sections of body panels...
For sections of body panels that are radiused or difficult to access, both sanding discs and polishing pads are available in 3-inch diameters.
Furthermore, color sanding-or dry sanding-is an evolution of the wet sanding process. The end results of both are the same, but Rodney prefers color sanding. "Wet sanding is an older process where you actually lubricate the paint surface with water. Dry sanding is a newer process that's much faster since you don't have to wipe the water off of the car every few minutes to see how much progress you're making," Rodney opines. "Wet sanding is more cumbersome, since you have to use a block to make sure you're applying pressure to the paint evenly. In reality, the end result is same, but some states now have regulations that outlaw wet sanding because they don't want the sludge it creates running into storm drains. It's only a matter of time until other states adopt similar policies. Color sanding shouldn't be confused with block sanding, which is performed after laying down primer in order to remove pinholes, waves, and scratches from the surface of the body."
What We Did
Color sand the hood off of a '69 Camaro
A slick, mirror-like, show-car finish
$300 - $500
To illustrate the dramatic before and after difference of color sanding, we left half of this Camaro hood untouched. As you can see from the reflections, the untreated half is stricken with orange peel and yields fuzzy reflections. The color sanded half, on the other hand, is as smooth as glass and features crisp, mirror-like reflections.