MY YOU TUBE CHANNEL ON BUILDING AND FINISHING GUITARS

[mostlyrite]

Jim's absolutely correct, Dan...

I tell my students (I teach modelmaking at University level) that paint and clear coat don't ever hide defects, they only magnify them.

Therefore, the aim in prepping a wooden body to receive a paint finish of high quality, is to get it defect-free, and keep it defect-free, by dealing with any defects that show up, after each step in the finishing process.

Raw body--after shaping, sand carefully with coarse (100 or 120) aluminum oxide sandpaper, gradually moving through the grades to #150 or 180 grit. Sand scratches MUST be dealt with, with each successively finer grade being used to remove the previous grade's scratches until there is nothing showing to mar the finish.

You will find that metallic, pearlescent, and mica glamor finishes show sand scratches much more readily than bursts and solids. A solid (non-metallic!) black, red, yellow, pastel green or blue, etc. paint finish will be quite forgiving of sand scratches, provided you are clear-coating, final wet-sanding, and buffing. Otherwise, sand until it's as smooth as possible!

If there are nicks, dents, gashes, that cannot be sanded out without compromising the body's shape and sculpting, you have a choice of filling and somehow hiding the fills...this depends upon how big the defects are and where they're located. If you can fill them, sand them smooth, and cover them with either a solid or metallic or pearl/mica color, or possible they're around the edges of an opaque burst, you're home free. This factor may affect your color choice...

Once it's level, defect-and-scratch-free, and smooth, you can spray some sealer onto the body. However, first you should blow off the dust with an air blowgun, and then carefully tack-cloth the surface to pick up any remaining dust.

Sealing can be done with either clear nitrocellulose (I buy mine in gallons from LMI) or vinyl sealer (also LMI). Thin the can consistency about 2:1 with lacquer thinner or universal reducer. (2 parts sealer to one of thinner or reducer). Let this dry nice and hard--about an hour in the sun, or two or three hours indoors at 60 degrees F.

Sealing raises the grain, so you'll need to re-sand with #320 aluminum oxide paper, dry. This will remove nubs and any other foreign matter that may settle into the sealer. Now, blow and tack-cloth again, and spray a couple of more coats of sealer. Check again for dust nits, nubs, raised grain, etc, and sand smooth with #320, dry again. Try not to cut through the sealer into bare wood.

Now, you're smooth enough to spray color or burst. Follow with catalyzing clear varnish, mixing according to the can instructions. I use PPG EC-700, catalyzed with ECH-7080 and then thinned with DT-870. The thinning ratio for guitars is thinner than for cars. I mix 4 parts of EC-700 with 4 parts of DT-870, and then catalyze with 1 part of EC-7080. Pot life is 3 hours @ 70 degrees F.

Clear coat (varnish) should go on over an UNSANDED color coat finish. Sanding shows, especially where metallics and pearls are concerned. Try to spray clear within 24 hours when possible, over a dry, virgin finish that's beenj carefully tack-clothed. If there are occasional dust specks in the clearcoat, they will come out when you wet-sand with #1000 grit wet-or-dry, lubricated with a 50/50 mix of water and Windex or equivalent glass cleaner.

Last, you'll buff either by hand or on a wheel using medium compound and then 3M swirl Remover. Wax with a good quality wax and assemble.