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Sylvan Wells Guitars
(781) 361-1471
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A Lacquer Finishing Schedule |
Everyone who builds a musical instrument wants to achieve a professional finish on their instrument. Of all the processes in building, this is probably the most difficult to achieve. It can be done. However, there are several important points to consider in achieving a professional finish. I have attempted to describe those critical points in the process and describe how I paint my instruments. My processes seem to evolve with time. Therefore, what is described below is my current finishing schedule (as of May, 2008). I have tried to give the reader a thorough explanation of the process and its’ pitfalls. With a little luck, anyone building an instrument should be able to achieve a professional finish by following the steps below. Initially, the guitar must be finished sanded with a flat block and 220 grit sandpaper. There should be no discernible scratches anywhere on the instrument and the entire instrument should be sanded flat. This is difficult to accomplish with the guitar “dry” (no finish) but you will find any scratches left on the instrument after the application of the first shellac coat. If you find scratches remove them before proceeding any further. If you do not remove them, they will show through the final finish. You do not need to sand with any finer grit of sandpaper. At this stage of the finish process you also need to thoroughly inspect the guitar for any holes, cracks, indentations, etc. on the instrument. Usually there will be areas around the binding and purfling. These should be filled with medium superglue and scraped and block sanded flat ( a razor blade works great for this). A careful inspection of the guitar should reveal no flaws in the instrument - any problems should be fixed NOW. Once the instrument is completely block sanded (basically “block sanding” means never using sandpaper without a flat block behind the paper - NOT YOUR HAND OR FINGERS) with 220 grit paper, apply one coat of shellac. Some finishers use shellac, others use sanding sealer or a vinyl sealer. I have found that sanding sealer works fine but I prefer shellac. If you are going to use a sanding sealer, then always use sanding sealer and thinner of the same brand of lacquer to be used on the instrument - DO NOT MIX BRANDS. This should be a “wash” coat. A “wash” coat is a very thin coat of sealer or a 1-2 lb. cut of shellac. Let dry for an hour. After the wash coat has dried, inspect the guitar carefully for scratches. You will find some. Using 220 grit and a sanding block sand the scratches away. Lightly sand the entire guitar. YOU ARE NOT TRYING TO REMOVE THE WASH COAT - MERELY SMOOTHING THE FINISH. At this point the guitar should be devoid of scratches and defects (pits, holes, etc.) and relatively smooth to the touch. Now apply two coats of 1 lb. Cut of shellac or sanding sealer (mixed 1/2 sealer-1/2 thinner) one hour apart. Once dry sand the instrument lightly to remove surface dust and imperfection. DO NOT SAND TO BARE WOOD. If your instrument is made of a porous wood (mahogany, rosewood, etc.) as opposed to non-porous wood (spruce, maple, etc.) then the porous wood must be sealed with a pore filler. The purpose of this step is to completely level the guitar so the lacquer finish will be level when finished and buffed to a high gloss. There are many commercial pore fillers on the market. However, several years ago I started using Starbond medium viscosity super glue as a sealer. Rub it all over the area to be covered with a paper towel. I do this in four steps: the back, 1/2 of the side, the other side and the neck. Do it quickly and then let it dry thoroughly. Now sand with 220 grit until all of the glue is gone and the guitar is flat (the pores are filled). Do not be afraid to sand through to bare wood. If necessary repeat the procedure. Usually rosewood requires two coats; mahogany one. Once completed, inspect the entire guitar carefully that there is no excess filler or glue left on the instrument and all scratches and defects are removed. If not repeat the above processes. If everything is satisfactory you are just about ready to begin the actual lacquer finishing process. Using a paper towel, wipe two coats of shellac on the instrument one hour apart. Once dry, sand the instrument lightly to remove surface dust and imperfection. DO NOT SAND TO BARE WOOD. Set the instrument aside overnight. In 2004, I began heating my lacquer before spraying it. It flows much better than spraying at room temperature. How I do that is described in another article. Apply a heated coat of lacquer (2/3 lacquer-1/3 thinner) to the instrument. Make the first coat a very thin coat. Let dry at least an hour. Now apply two heavier coats of heated lacquer (2/3 lacquer-1/3 thinner) at least one hour apart. Let dry at least overnight. Then apply three more coats of heated lacquer (2/3 lacquer-1/3 thinner) at least one hour apart. Let dry for at least two days. THESE PROPORTIONS MAY BE DIFFERENT WHERE YOU LIVE. THE HUMIDITY IN MY SHOP IS 45%. IF YOUR HUMIDITY IS HIGHER YOU WILL PROBABLY NEED TO ADD RETARDER (5-10%) TO YOUR MIX. If you have followed the above instructions you are ready to do “block sanding” of the instrument. Block sand the entire instrument with 320 grit paper dry. Do not be concerned if you sand through to bare wood. The purpose of this step is to insure that the guitar finish is completely level. The easy way to tell if this is the case is that the lacquered guitar will be very shiny and after sanding will be uniformly dull; however, where the lacquer is in a pore beneath the surface it will show as a shiny spot. You must sand until there are no shiny spots left on the instrument and the entire guitar finish is dull. This is also the time to do any filling of holes or binding cracks, or leveling spots on the instrument. If the hole or spot is not too deep, you can fill with lacquer. Otherwise use thin or medium superglue. THIS IS THE MOST IMPORTANT STEP TO OBTAINING A QUALITY FINISH. Once the guitar is completely level (devoid of shiny spots), apply three coats of heated lacquer (2/3 lacquer-1/3 thinner) at least one hour apart to the entire guitar. Let dry for at least one day. Then apply three more coats of heated lacquer (2/3 lacquer-1/3 thinner) at least one hour apart to the neck, back and sides of the guitar. Let the entire instrument dry for at least two weeks. Once the lacquer has cured for at least two weeks, it will appear very shiny but still not look like a fine, hand finished guitar. To obtain this next level of finish, you must block sand the entire instrument as before, this time being careful not to break through the lacquer finish. SAND CAREFULLY! STAY AWAY FROM THE EDGES AND CORNERS! Use 400 grit to get the instrument close to level and then switch to 600 or 1000 grit to finish up the process. Once you are finished the guitar should be silky smooth and completely dull in appearance. If all has gone well, you are finally ready for final rubbing or buffing out the instrument. If you do not have access to buffing wheels you can buff by hand. If you have access to buffing wheels you probably don’t need the information in this article. Without buffing wheels use Meguiar’s #4 and Meguiars #7 polishing compounds. Start by using the #4 and a soft rag. Rub the compound on the instrument until the compound disappears. The instrument should now have developed a glossy look but not quite as glossy as you want. Now repeat the process with #7. This is a fine polishing compound and the instrument should now be glistening! Carefully inspect the entire instrument. Polish any place you missed. Clean up any residue with a toothbrush. Congratulations! The instrument is gorgeous!!!! MATERIALS I USE AND RECOMMEND Medium Viscosity EM -150 Starbond Super Glue Meguiar’s Polishing Compound #4 Meguiar’s Polishing Compound #7 If you have any problems with this schedule, I am happy to discuss it. E-mail me at sylvan@wellsguitars.com.
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