Tom,
There are two stages of the paint process when you can wet sand. The first
is the final sanding of the primer coat before painting. The second is after
the paint has dried before polishing.
I'm sure others have different techniques for wet sanding but this one was
taught to me by a buddy who produces consistent show winning paint jobs.
The pupose of wet sanding the primer is to produce a MUCH smoother paint
finish. The technique I use involves a five gallon bucket of warm water, a
few drops of dish soap, a large sponge, 600 grit 3M Wet or Dry sand paper
and a can of cheap flat black spray paint. I do not use a sanding block for
wet sanding. The procedure starts by applying a "guide coat" of flat black
spray paint. This coat should be nothing more than hazy black stripes a few
inches, 4" to 5", over the entire piece to be sanded. You don't want to
make solid black stripes, they should look a little heavier than just over
spray would. The purpose of the stripes is to indicate where you have
sanded and where you may have missed a spot. I start by soaking the
sandpaper for about 30 minutes to soften up the paper. This makes the paper
backing more plyable. The actual process of sanding starts with me cutting
each sheet of paper into thirds and folding the piece I'm going to use into
thirds. I "load" the sponge with water, wet down the area where I'm going
to start and then begin sanding in a circular motion. You need to be ver
cafeful not to sand with your fingertips. This can cause shallow groves in
the primer coat. Instead, keep the paper back under you fingers, say from
the first knucke down. This gives good even sanding pressure. Be sure to
take off and rings you might normally wear and even trim you finger nails.
The finger nail thing sounds funny but I have seen "sanding scratches" from
a buddy of mine that has particularly thick finger nails and bad sanding
technique. There are times when you will have to use you fingertips to sand
but just go easy when you do. As I sand with one hand, I keep a constant
trickle of water running from the sponge. You can tell when you aren't
using enough water when the paper sticks to the surface. Be sure to dip the
paper in your water bucket fairly often to rinse of the "sludge" that builds
up on it. I continue on in this fashion until all of the guide coat is
gone. I finish the wet sanding procedure with a good wash job, water with a
tiny amount of dish soap, of the entire piece and a complete drying with
disposable towels. In my experience, if I have done a propper job of
sanding, the primer will actually have a low shine to it.
Wet snading the finished paint before polishing is done with the same basic
technique with a few exceptions. First and foremost, do not spray a guide
coat. Second, at this point I actually sand the entire piece twice, once
with 1500 grit and once with 2000. After the water has been dried from the
sanded piece any area you missed will be glossy. Once all the missed areas
are sanded you can polish the paint. I don't do the polishing so I can't
comment on the procedure.
I hope this rather long winded explination helps.
Robert Rogers
57 Belair Sport Coupe restored to original
55 -2 3105
55 -2 6400
55 -2 3100 Wife's project
57 3100
82/86 GMC Sierra SLE Crew Cab 1/2 ton short bed (For Sale)
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