Most finishes on a guitar are not only there for aesthetic reasons but also to protect the material the guitar is made of. However, the finish has an effect on the resonance of the guitar, changing the way it sounds.
It helps keep moisture away from the body, especially if you live in humid conditions, as well as keeping dirt and grime from getting into the wood.
In the guitar world, the main two finishes you’d find on a guitar are polyurethane and nitrocellulose finishes. Each finish has different characteristics, so it is important to look at both before deciding which guitar and finish you prefer. This is especially true when purchasing acoustic guitars but can also be applied to electric guitars, although the influence on sound is less.
There are a few other finishes you might find on guitars, although scarcer, and I’ll take a look at them as well in my in-depth look at…
The Different Types of Guitar Finishes
Nitro finishes are found on older electric guitars from the ’50s and ’60s.
A nitro finish is done over a period of a few days. Each layer essentially melts the previous one, creating a nice gloss layer over the wood. This finish can be found on classic 50’s and 60’s Fenders. Although Fender stopped producing nitro-finished electric guitars around the mid-1960s, switching to polyester coatings.
Acoustic guitars can still be found with this finish, as well as most wooden furniture.
Allows the guitar to breathe…
Nitrocellulose lacquer is made from mostly plant-based substances. Most luthiers will attest that the thinner layer created by a nitro finish will allow the wood to breathe better, thus providing a louder and greater sustain to the guitar sound.
The biggest issue with a nitro finish is also the reason that makes it so good. The thin layer means that the guitar is more susceptible to cosmetic damage. Another issue is that the nitro finish will degrade over time, which means it will need to be coated again eventually if you want to keep the glossy, protective layer.
Nitro also doesn’t cope well with regular temperature changes. It tends to crack over time, especially if it travels around a lot between areas of different humidity. However, there are products specially designed to stop the damaging effects, so check them out in our review of the Best Guitar Humidifiers you can buy.
Polyurethane and Polyester finishes
For modern guitars, polyurethane and polyester guitars are considered the standard. After the ’60s, poly guitar finishes replaced nitro finishes, and things have basically stayed that way since then.
The decision to switch came from a few factors. Nitrocellulose became a strictly regulated substance after assessing the damage a high-volatile-organic compound such as nitrocellulose could do to the environment. Nitrocellulose also doesn’t last as long, which means it will need to be reapplied after a couple of years, which also doesn’t help the environmental issues with nitro finishes.
Quicker and stronger…
Polyurethane and polyester finishes are safer and better for the environment. They also do not require the time-consuming process of applying multiple layers; instead, a single layer is more than enough to get a thick coating on the guitar.
This means that polyester and polyurethane finishes are much stronger than nitro finishes. They won’t crack easily over time and can take a few bumps without damaging the guitar.
However, purists argue that because of the thicker coating, it subdues the sound of the guitar somewhat, especially on acoustics.
Epoxy is essentially a type of polyurethane but is not used on guitars much. It is an epoxy resin and a polyamine hardener mixed together.
This finish, if done correctly, which is difficult to do due to the viscosity of the epoxy, can be very hard. This means if sanded well, it can produce a really nice gloss finish that is completely see-through, as well as being resistant to yellowing over time.
A UV finish, mostly found on modern wood floors, is now also used for some guitars. A UV cured coating is created by using an ultra-violet light that dries the coating with irradiation of the UV rays. The coating is pre-applied before being placed in the oven, where it dries immediately.
This finish looks similar to a nitro finish but is more durable and faster to manufacture. It is also VOC free, unlike nitrocellulose.
Types of Guitar Finishes – How aging over time changes your guitar
As stated, over time, the coating might get thinner, especially if you own an older, nitro-finished guitar. This will result in the guitar’s tone changing. The thinner the coating is, the more vibration and resonance it will have.
Time will also change the guitar tone. Humid conditions can make the wood absorb more moisture. This results in a slightly dumbed-down or drowned-out sound that is less resonant.
Humidity also affects the strings and will also cause them to rust faster.
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And don’t miss our helpful guides to Exercises and Tips For Better Finger Dexterity, the Different Types of Guitars You Should Know, or The Different Types Of Chords You Should Know to improve your playing.
Types of Guitar Finishes – Final Thoughts
If you are purchasing a new guitar, it will most likely have some form of poly coating on it. However, if you are shopping secondhand, you might be able to find a classic vintage Fender that still has the original nitro finish on it. However, it’s not going to be cheap to buy.
For me, especially when it comes to electric guitars, the finish does not alter the sound so much that I feel the need to look for nitro-finished guitars. If you are shopping acoustic, though, a nitro finish will definitely result in a brighter sound with more sustain.