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Jim Wilson
 
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Default Pinewood Derby 101 - painting a car and getting a smooth finish - need help

usenetdg wrote...some questions about finishing the car.

First off, I've never seen a really nice looking brush-on paint job on
one of these cars. My son brushed on his first one, and was very
disappointed with it, so I cleaned off his paint with lacquer thinner
(well-ventilated area with a fan, and use gloves!) and taught him how to
spray it. At that age, his little hands couldn't hold down a spray can
button very well, but this was easily remedied with one of those cheap
aftermarket gun-like squeeze handles.

Sand the bare wood to 180 or 220 grit. Use a light touch and a lot of
back-and-forth strokes with the grain. Start with 60 or 80 grit, and
don't skip any grits. Shouldn't take more than two or three minutes per
grit at the most, and probably less. When you're finished, clean off the
dust with a rag at least; a tack cloth or vacuum is better.

Run a fairly stiff wire through each of the axle slots. It needs to stay
in the slots, so you can lift and turn the car over by the wires, but it
shouldn't be so fat as to "waller-out" the slots and make the axles
loose. You want to be able to suspend the car on the wires between a
couple of bricks or something, spray the bottom, flip it, and spray the
top.

You will need a couple cans of paint: whatever color he wants, the
primer, and optionally a can of clear. Avoid multi-color schemes, pin-
striping, and other complexities for his first year. Decals after,
though, are great!

I like Krylon, but we used Rustoleum products with equal success. It's a
good idea to stick with a single brand, though, as mixing brands can
sometimes cause crackling, especially with the clear coat.

Spray a very light coat -- a dusting really -- of the (wood) primer. You
should still be able to see the wood grain through the coat. Wait five or
ten minutes and spray another coat just like the first one. Another wait,
another coat, and the wood grain should be completely hidden. Let this
coat dry for about 30 minutes, and then lightly sand it with 320 or 400
grit. Don't go through the primer to the wood, just sand the primer. If
you do sand too deeply, shoot another coat and sand again. You want a
smooth finish of primer.

Dust it off, and shoot the first color coat. Resist the temptation to
shoot a heavy coat, trying to go for the glossy look. Again, you should
be able to see 50 to 20% of the primer through the first coat of color.
Again 5-10 minutes wait, and shoot coat number two. This coat should
just about completely color the car; not much if any primer still
showing. Too light is better than too heavy. If much primer is still
showing after coat two, wait your 5-10 and do another.

By the way, other than after the final primer coat and now, the waits
between coats should be only five to twenty minutes max, just until the
paint is dry to the touch. If you wait too long, overnight for example,
you increase the risk of crackling the paint.

For a really smooth look, let it dry 30 minutes to an hour this time, and
then sand very lightly using 600 grit wet-or-dry paper with just a drop
or two of water to keep it wet. Wipe off the slurry with a slightly damp
rag. An old T-shirt is perfect.

The condition of the surface at this point should be baby smooth, with
maybe a few very small spots of primer showing. Shoot the final color
coat. This coat should be *just heavy enough* to wet (not soak) the
entire surface. Be sure to do the bottom first and then the top.

After the final color coat, your son will probably be pleased as punch
with his finish. If so, I'd say you're done. If he really wants to go for
the extra-fancy-super-high-gloss look, he can add a coat or two of clear.
However, this introduces the greatest risk of crackling, especially if
any of the previous coats have been too heavy, or if the clear is applied
too heavy. The clear should be applied just like the final coat of color.

Good luck! These are some good memories.

Jim