Your Instrument's Finish
Let's consider for a while a component of your instrument that is often overlooked: its finish.
An instrument's finish is not just for beauty; its main purpose is protecting the fragile woods used in the instrument's construction from the ravages of the elements. Moisture and body oils can penetrate the pores of the wood, causing distortion in the wood's surface and damping the ability to transmit sound. Excessive dryness can cause cracks and splits in the wood. Even the sun's ultraviolet light can bleach the color from some woods while darkening and discoloring others. The finish on your instrument is designed to eliminate, or at least minimize, the effects the elements can have on your instrument.
The finish techniques developed over the centuries have become very effective for their intended purpose, but the finish itself must be cared for or much damage can result. The best finishes are somewhat fragile themselves; the reason for this is that while the finish must protect an instrument from the elements, it still must allow the instrument to function as a finely tuned and delicate mechanism for sound production. Many instruments over the years have had their sound-producing capabilities destroyed by thick and tough finishes that did not allow the parts of the instrument to vibrate properly.
Following is a brief overview of the more prominent finish techniques to emerge over the past few centuries:
Violin varnishing, as the name implies, is a technique devised by the "old masters" of violin making. Violin varnishing involves hand-rubbing a thin layer of oil-based varnish over a mineral-particulate-rich layer that is first applied to the surface of the wood (much as a painter applies gesso to canvas prior to painting). While violin varnish is an exceptional finish acoustically, it is very delicate and offers little protection from the elements or from minor "bumps and bruises". There are as many techniques to varnishing as there are makers who practice the art, all of whom attempt to recreate the finishes used by historic Italian makers such as Nicola Amati, Antonio Stradivari, and Andrea Guarneri. Violin varnish is still used by the finest modern makers of violins, and is favored by some mandolin makers as the mandolin was developed with the violin as an acoustic model. The Gibson company used a violin varnish finish on its mandolins until 1929, and these are considered to be among the finest mandolins ever made.
French polishing is a method of applying shellac to an instrument's surface. Despite the term "French polishing", no polish is used in this method of finish, and it is generally agreed that the term might have received its name from the extensive rubbing that is necessary to apply shellac smoothly and perfectly. French polishing yields a very nice finish from an acoustic standpoint, but the finish is extremely delicate and can easily be damaged even by a fingernail. Classical guitars have weaker vibrational energy imparted to their tops by gut strings, thus the acoustic "transparency" of French polish is of particular benefit to the classical guitar. This offsets the fragility of the French polish finish, and French polishing is generally considered by purists to be the best technique for finishing a classical guitar.
Polyurethane is a modern sprayed-on finish that attempts (unsuccessfully) to reproduce the appearance of violin varnish without having to do much work. It is a very tough finish, but acoustically inferior, and is generally found on cheap imported instruments.
Nitrocellulose lacquer is a sprayed-on finish that is very durable and easy to touch-up, yielding exceptional acoustic properties and excellent protection when applied properly. As nitrocellulose lacquer is a sprayed-on finish, specific techniques must be used: the finish must be applied in a sealed environment so that no dust or impurities are introduced, and spraying techniques must be precise and uniform to avoid imperfections. Nitrocellulose lacquer should be applied in coats, with hand-rubbing applied between coats for a uniform and thin final finish. Nitrocellulose lacquer is used by many instrument manufacturers today, but modern production techniques do not allow for the hand-work required to achieve a fine, thin finish; thus many instruments from even some of the more prominent makers have their tone impeded by a thick, inflexible finish. When applied evenly and with thin coats, nitrocellulose lacquer is the best all-around finish for acoustic steel-string guitars, as well as banjos and mandolins. Properly applied, nitrocellulose lacquer offers the same level of acoustic transparency as violin varnish, but with much better protection. The C.F. Martin guitar company has been using nitrocellulose lacquer on its finest instruments since 1926. Modern spray booths, used with "old world" hand-rubbing techniques, allow not only for proper spraying, but also for proper drying both between coats and after the finish is complete. All CB instruments are finished with thin coats of hand-rubbed nitrocellulose lacquer.
When applied using proper techniques, materials and methods, the finish of a fine instrument should compliment the sound of the instrument and protect the delicate woods of the instrument for a lifetime given proper care. All of my instruments are finished with this in mind, and I cut no corners in assuring that these principles are followed to the finest detail.
Next time, we'll discuss how to properly care for the finish of a fine instrument.
Last modified: March 20, 2019
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