Saturday, December 4, 2010

How to get a great guitar finish using spray can lacquer

The J Bass and Les Paul builds are explained elsewhere in this blog so here I'd like to concentrate on how to achieve a very high gloss, durable and acoustically sound finish using standard automotive spray lacquer from Plasticote.  These cans are available from automotive supply stores and I chose them because they are nitrocellulose lacquer.

First shake the cans well and heat the cans in a warm water bath before spraying.  Be careful not to get any water in the spray nozzles and always hold the cans upside down and spray to clean out the nozzles once you are done spraying so that they don't get clogged with lacquer.

Prep the body of the guitar with sanding sealer to achieve a uniform smooth surface.  Your final finish depends upon a smooth, clean base.  If you are spraying a solid color, you might consider using a primer in place of the clear sanding sealer.  Mount the guitar body on a support so that you can comfortably hold it while spraying.  Here you can see the body and neck of the J-bass drying during the finishing process.

 Build up several coats of clear gloss lacquer over either the colored paint (in this case) or sanding sealer (in the case of a natural wood finish like my Les Paul and the neck shown here).  I use eight or more coats, sprayed with about a 1/3 overlap for each pass.  Always start the spray just outside the edge of the body and continue to spray all the way past the other edge of the body.  Also make sure that you keep the can perpendicular to the body as you make your spray passes.  If you just pivot the can from side to side, you will get a lot of paint in the middle and little to the sides.  Try to avoid staying in one place for any length of time as this will cause runs. Lacquer dries very quickly so you can spray new coats after about an hour's drying time so it doesn't take long to build up the coats.  Always spray in a well ventilated area and wear appropriate respiratory mask protection.  Leave the body and neck sit for at least a week to allow the lacquer to cure.  Your body should look like this, with lost of little bumps all over it.  This is sometimes called "orange peel" and is cause by little bits of over-spray from the very edges of your spray patten that dry as humps because the lacquer sets so quickly that the surface tension doesn't have time to flatten the finish out completely.  The next steps are aimed at flattening the surface and returning a high gloss.
I've masked off an area to demonstrate the final finishing process.  First get a bucket of clean water and sand the area with water soaked wet/dry 600 grit paper.  The water helps keep the sand paper from clogging with lacquer.  It also makes the paper less aggressive in it's removal of clear coat. Don't press very hard while you do this for fear of cutting through the lacquer.  Be very careful about sanding on sharp or curved edges because you can very quickly cut completely through the finish.  Frequently dip your paper in the water and if you see any color (blue in this case) in the water, stop, dry the piece off and wait a day before going back to re-coating the body in clear lacquer.   The idea behind building up eight coats is to make a thick enough clear finish so that you don't end up cutting through to the paint.   Stop once you don't see any more "islands" of gloss in the "sea" of flat finish.  This is a good time to talk about the difference between gloss and flat.  As you can see here, we've turned a high gloss (and bumpy) surface into one that is flat just by sanding it.  A gloss surface is completely smooth with nothing to diffuse the light off of it.  Flat paints have small amounts of imperfections suspended in the paint that diffuse the light off of the surface.  You can create the same effect by introducing scratches in the surface that also diffuse the light like we did here.  Everything that we do from here on is aimed at using finer and finer grit abrasives to remove the scratches from the previous sandings.  This is the key point.  If you understand this you know everything you need to to make a really great finish.
 From 600 grit we move to 1000, 1500 and finer if you have it.  Each successive grit makes the scratches finer and finer.  Next move on to rubbing compound  which is also available in automotive supply stores.  Rubbing compound has suspended abrasive in a paste and is applied using a clean cotton rag.  After the rubbing compound you will get a hazy finish that is much glossier that what we started with.
 After the rubbing compound, move on to a finishing compound that has an even finer grit abrasive.  We are getting close but there is still a bit of haze to the finish.
 Lastly, use McGuire's Scratch-X and prepare to be blown away by the finish!  All of the haze is now gone and you can see the finest of details reflected by the surface.  I put a couple of coats of paste wax or automotive wax over this finish to help protect it.   I hope this helps you achieve the kind of stunning finish that will get your guitar noticed by everyone who sees it.


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  2. are there any chances of me getting a perfect finish on my first try?

  3. No reason you shouldn't get a great result if you put in the time and effort.

  4. Thanks for the info. I am doing a custom paint job on my Ibanez RG and I just finished clear coating my airbrush work. I'm guessing I can replace the rubbing and finishing compound with Mc guires Fine Cut Cleaner, and perhaps substitute Scratch-X with Swirl remover?

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