Wetsanding Tips

Hey guys, in spite of trying to touch up a few spots on my Stratus, i've learned the hard way that it really isn't as simple as taping-off and just spraying out. Here's a great article that I peices all into one post to show some great techniques of Wetsanding. If you ever get into automobiles/boats/bikes anything that needs to be restored or made to look somewhat cleaner or newer, this can definately help you out.

Enjoy.




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The Cure

We provided some practical tips on prepping and painting in previous articles, but there are still some extra steps involved to get the most out of the new hues. As pro painter Mike Face points out, "Paints require more work today. If you look closely at the reflections in the surface, you can see that the edges of, say, tree branches or a stop sign, don't look quite as crisp as with those lacquer finishes." Face believes that the best way to get that old-time shine is to first let the initial clearcoats cure in the sun for a couple days so the solvents air out. Next, block-sand the clearcoated surface with 1,000-grit paper and water, then apply two more coats (in addition to the two or more previously applied). These last applications are sometimes called "flow coats." Face then sands yet again with 800 and 1,500 grit paper and water, and proceeds to buffing the finish.

Sanding Tips

Face shared some tips and tricks he uses during color-sanding, such as adding a bit of dish soap to the water. "That avoids paper clogging," he says. "It's also good to let the paper soak, and have a wet rag in the other hand to wipe off the residue."

One paint flaw that requires correction is orange peel, that bumpy surface caused by contaminants (see previous article for details). It may not be immediately evident (unless it's a severe case), but when you begin sanding and buffing, the residue reveals the raised areas of the paint.


Color-Sanding and Buffing
Bringing out the shine of a fresh, new paint job

Like color-sanding, buffing can be a tedious and time-consuming process. Face starts with a white foam pad and a coarse polishing compound, working a small section at a time. After a couple of passes, you can actually feel the difference in the smoothness of the paint with your hand. Then he goes over the surface with a softer, black foam pad and a finer polishing compound.

When it's all done, Face discourages waxing new paint for at least two months in order to let it cure properly. He actually prefers using the fine polishing compound instead of wax, but he likes the thinner detailing sprays as well.

Does that all sound like a lot of work? Sure it does, but that's why custom paint jobs cost so much (figure on a minimum of $6,000, if not much more). Face admits that this extra effort and expense may not be worth it for a "street job," but on a show-quality car that's under close scrutiny, it really pays off. Our next story about this particular GTO resto will cover upholstery.


Color-sanding with fine-grit paper and a soft block is needed to get the most out of today's two-part urethane paints.


A few drops of dish soap in the water for color-sanding helps to reduce paper clogging.


While color-sanding, keep a wet, soapy rag in your other hand in order to quickly remove any paint residue.


Use a rubber squeegee to wipe off the water and inspect the finish


Color-sanding removes those small bumpy areas otherwise known as "orange peel.


After color-sanding (along with spraying on additional clearcoats if needed), apply a buffing compound.






The final buffing compound is much finer to remove any swirl marks and bring out the shine. Wait at least two months before waxing a newly painted body


You can both feel and see the difference in color-sanded and buffed paint.



And here's a shorter How-to text-only version.


Sanding tips
Wet sanding is normally done by hand. Never use an electric powered sander when wet sanding or you could get electrocuted. We have used air-powered dual action (DA) machines for wet sanding (which is messy), but we usually sand by hand.

I use a hard rubber sanding block like the one in the photo to hold the paper when smoothing and abrading most surfaces. A curved or soft pad may be necessary on curved surfaces, but you can wet sand without a block or pad by simply folding the cloth to fit your hand and dipping the paper in water. On heavily irregular or textured surfaces such as a sculpture, the waterproof paper won't contour enough, so use an abrasive pad like 3M Scotch Brite™ with water.

I usually put water in a bucket. If the shop is cool, I'll put hot water in a cooler (it holds heat as well as cold) to help keep it warm. I dip the rubber sanding block with sandpaper attached into the water when more water is needed. Another approach is to fill a squirt bottle and spray the substrate as you're sanding.

Use a rubber-bladed window washer squeegee to scrape excess water and cut material from the substrate so you can visually inspect the surface better. When wet, the surface is shiny, but when squeegeed, it appears dull and highlights surface texture. When wet sanding, especially with aggressive grits, you have to keep an eye on your progress. Rinse and squeegee away water between changes in grit to avoid contaminating the finer grit with the previous coarser grit. Be sure to remove any remaining debris right after wet sanding because it's hard to remove after it dries. Rinse water should sheet evenly, without beading or fisheyeing. If rinse water beads up, wet sand again until the beading is eliminated.

To prepare the surface for subsequent epoxy coats or painting, wipe the dry surface with a paper towel to loosen any remaining debris and then sweep it with a bench brush. Don't use rags-they may contaminate the surface. Follow with an electrostatic dust cloth, such as a Pledge Grab-it™. We use a tack cloth prior to painting, but not for subsequent epoxy coats because the tack cloth is resinous saturated cheesecloth which can contaminate the substrate and interfere with epoxy adhesion.

Constant immersion in water softens your skin and makes hands more susceptible to cuts and abrasions. Wet dry cycles can also result in chapped skin. Use a dry skin cream such as Pond's™ to combat this problem. If you wet sand with the paper in direct contact with your skin, it's possible to abrade your skin away. I've been without fingerprints for a few days as a result. The upshot is, your hands will be cleaner than they've been in years, possibly with fingers a safecracker would envy.

Wet sanding can make a mess. All the cut debris in solution with water ends up on the floor. This is difficult to sweep up when dry. But the advantage, as mentioned before, is that wet sanding produces no dust.

Much of the quality of a final finish is in surface preparation. Wet sanding has much to be said for easing the task without sacrificing quality.