While the guitar itself has evolved throughout the years, the types of finishes used have remained pretty consistent -- nitrocellulose Lacquer, polyurethane, and polyester which are still the standard. Aesthetics aside, does the finish actually affect tone? Guitarists and musical technicians are somewhat split on this issue, with some going as far religiously sticking to one particular type. Keep reading to find out about the major differences between nitro and poly guitar finishes.
Nitrocellulose Lacquer has been around since the 1920’s, this type of finish blends with paint really well and is also used by car companies as well. Nitrocellulose is solvent based, a plant based substance usually made from cotton and is combined with nitric and sulfuric acids, when the lacquer has been applied the solvent chemicals dissolve and leave behind a resin which is buffed and sanded until a gloss is attained. Nitro finished layers are easily repaired and restored while also being less constricting and rigid than other types of finishes. On the downside Nitro is not the most durable type of finish, it can wear away and is softer, materials such as guitar stand rubbers can sometimes react with the resin much in the same way as a solvent does. Changes in temperature also can cause small cracks to form in the finish as the wood underneath expands and contracts.
Meanwhile, polyurethane and polyester finishes have been in use since the late 1960’s while in the last few decades they have become more popular as they don’t share the same complications of nitro finishing while being glossier and more durable. The synthetic resin leaves virtually no solvents during curing. Poly finishes completely harden and solvents cannot break them down, Poly finishing is very resistant to cracks, dulling and scratching while also being durable. If you want the new shine finish to last a long time, as long as you have your guitar, then a Poly finish is what you want. Nitro finishes eventually end up having a vintage look and appearance while Poly finishes stay new looking and shiny.
Whatever your preference may be all finishes play a role in the effect upon the vibration of the guitar’s wood through the whole instrument. The effect is more noticeable on acoustic guitars while overall remaining subtle but enough that blues and jazz artists who rely on dynamics and resonance and less so on distortion as rock guitarists do the finish does in some instances represent a significant difference in performance and achieving different sounds. Poly finishes are getting thinner via modern techniques which further facilitates this resonance. Nitro is still widely used but it seems, aside from the boutique guitar market, soon it may become obsolete in practical use.
What the best for you may be is up to you to decide as you might prefer your playing experience to show in a more worn down looking instrument with a nitro finish or a poly finish that is glossy and matches your flashy stage clothes. Either way, you should always go with what sounds good/the best and if the look happens to match, don’t rock the boat. The finish certainly matters in the overall scheme of things but the tone ultimately lies in the fingers and not in appearance and cosmetics.