There are many design, process, and material choices to make when creating a musical instrument. One of the most perplexing for the inexperienced builder is choosing the finish. In an effort to help with this selection we present an overview of the finishes most often used on musical instruments – explaining the distinguishing characteristics, general application process, and compatible products for each. Following these general product descriptions, these finishes will be compared to help narrow your choice to the most appropriate finish for your needs and shop situation. And finally, in articles separate from this overview – accessible from the drop-down box in the upper left of this page, we provide detailed instructions for the application of five finishing products.
The materials that are used as musical instrument finishes vary greatly in their properties and application. Almost all of them were developed originally for general woodworking or furniture finishing and were later adopted as musical instrument finishes. For hundreds of years, basic oils and simple varnishes have been used as the protective coating for musical instruments, wooden furniture, and other wood products. Nitrocellulose lacquer, however, has been the primary wood finishing material, and American guitar factory preference, for over eighty years. More recently polyurethane, polyester, and other catalyzed coatings have been used in guitar manufacturing and the quality of water-based finishes has increased steadily so that now the best of them equal or exceed the quality of nitrocellulose finishes. The more exotic synthetic or catalyzed finishes are best suited to factory situations, not to the average small-scale guitar maker.
GUIDE TO SELECTING THE BEST FINISH FOR YOUR SITUATION
We hope the previous descriptions of our finishing materials have helped you decide on the best one for you. Each of these finishes can produce a good sounding musical instrument, so your choice may be driven more by your shop situation and the expectations for the type of instrument that you are finishing. Even with that said you will have several alternatives that will accommodate your situation or needs. The following observations may help narrow your choice further.
- If you intend to make steel string guitars for the commercial guitar market you will most likely need to use the tried and true solvent-based nitrocellulose lacquer system used on most other commercially available guitars. This, of course, requires a complete spray booth, compressor, spray guns, safety equipment, etc., and the space and resources for this equipment. The expectations of most store buyers are conservative and these buyers will usually not take a chance on guitars that are very different from the established brands.
- If you are making steel string or electric guitars and have spray equipment but want to avoid the use of hazardous materials your best choice is a water-based finish. When it is expertly applied it is almost as hard and durable as the solvent-based based product and can be virtually indistinguishable from it. A spray booth is useful but not required if the spraying is done in an open area with mild ventilation. Even some very experienced guitar makers with complete spray facilities and years of experience with the solvent-based lacquers are beginning to work in the water-based lacquers.
- If you are finishing a steel string or electric guitar without spray equipment your best choice is to apply a water-based finish by brush. This is slightly more labor-intensive and time-consuming than spraying but with careful brushing and sanding between coats, the results can be the same as with the sprayed finishes. The resulting finish will be durable and glossy as expected on these guitars and, of course, you will also have the benefit of working in a less-hazardous, less-toxic environment.
- If you plan to develop a full-service guitar repair facility you will need be able to spray solvent-based nitrocellulose lacquer because most of the acoustic and electric guitars you’ll see for repair are finished with it. French polishing is also very useful for most minor touch-ups on any finish.
- If you are making a classical guitar and already have spray equipment you may apply either a solvent-based nitrocellulose lacquer or the water-based finish. Although French polished shellac is held in higher esteem for classical guitars, many makers around the world have been very successful with these harder finishes. It is common practice now by many makers to finish the sides, back, and neck in a more durable finish and only French polish the top plate – getting the best from each finish. Those makers concerned with the hazardous and toxic nature of the solvent-based lacquer will use the water-based system.
- If you are making a classical guitar in the most traditional manner then French polishing is your only choice. Learning to professionally French polish requires patience, time, and serious attention and concentration to the process, but the same is true for traditional hand-bending of the sides, hand-planing and scraping of the plates, and hand-making of the mosaic rosettes. Mastering these and other traditional hand skills will take consistent practice and commitment.
- If you are working with minimal equipment and working space (possibly a small area or table in your home) your instrument can be effectively finished by either brushing water-based finish, French polishing shellac, or wiping on an oil varnish or shellac-based finish. Each of these finishes is non-hazardous and can be safely applied in your home with no more equipment than brushes or cotton cloths. The wipe on finishes are the absolute easiest to apply, brushing the water-based finish is slightly more involved, and French polishing requires the most practice and skill. The resulting instrument finish from any one of these materials can range from merely adequate to true professional level depending on your experience and skill.