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If you’re building a guitar from a kit — always an easy and fun way to learn how a guitar is made — your last major step before final assembly will be painting or finishing.
But what finish should you choose? Will painting a guitar affect its sound?
Painting a guitar can have some affect on the sound, depending on the kind of paint used, how much is applied, and what kind of guitar you’re finishing. The finish will most likely make a bigger difference on acoustic guitars than on electric guitars because the body resonance is key to an acoustic’s sound.
Let’s look into how the finish you choose can affect the tone of your instrument, as well as what kinds of finishes are most common and why they are used so often.
Does Painting A Guitar Affect The Tone?
The first and most important thing to remember when considering any kind of finish for your guitar is that a guitar’s body resonates and that helps produce the tone. On an electric guitar, the pickups are what capture the vibration of the strings, while an acoustic guitar uses the entire body.
That doesn’t mean the finish on an electric has no effect, as this video argues, the finish on any guitar can affect its tone.
If you think about how a guitar works, it makes sense that any finish could have some impact on the tone. That’s because the entire instrument resonates with the strings, and that, in turn, affects the vibrations of the strings themselves.
That will have an impact on the sound an electric guitar’s pickups capture. Whether the difference is good or bad, or even noticeable to most people, though is a different matter.
In some cases, which I’ll go into more detail about shortly, the finish can have a drastic impact, but for the most part, that isn’t the case.
People with a tremendous amount of musical experience and who have trained their ears might be able to hear some differences in tone in some situations, but as long as you are within some basic parameters, the differences will be minimal.
That’s especially true if you aren’t listening live, in a quiet room. Everything from ambient noise to the speakers or headphones used will have a much larger impact on how the guitar sounds than the finish.
And that’s not to mention the impact how a recording was made, from the microphone used and mic position, to the recording medium used, has on the tone of an instrument.
Does The Finish On A Guitar Affect Its Sound?
While for the most part, the finish of a guitar doesn’t have a major impact on the sound, there are some cases where you’ll be able to hear a difference. That’s especially true for acoustic guitars, which rely on the resonance of the top to amplify the sound created by the vibration of the strings.
Even in that case, though, the finish often has a far less dramatic effect on the sound than other things like the tonewood used, body size and shape, top thickness, the bracing used, and even string choice.
One situation where you might be able to tell a difference fairly easily is with an acoustic guitar that has a thick finish of standard paint applied either nitrocellulose lacquer or a polyurethane paint.
Both of those types of finishes have pros and cons, which I’ll cover shortly, but they are both applied in a way to make sure the instrument resonates freely and offers the best possible tone.
But if you run across an old acoustic that someone decided to “refinish” with a little house paint and a brush or roller, it won’t take you long to realize why that isn’t the standard way guitars are finished.
The guitar might still sound pleasant, but it will almost certainly be quieter and offer less sustain than a guitar with a standard finish. That’s because the paint makes the wood heavier and means it can’t vibrate as freely.
The thickness of the finish and the exact composition will have a big effect on how much vibration is absorbed. But that also needs to be put into perspective.
A thick coat of enamel paint would certainly inhibit the vibration of an acoustic guitar’s top. And if you listened to recordings of the same instrument before and after it was painted, you’d probably be able to hear a difference in the tone.
But other things, like the factors I mentioned above — tonewood choices, top thickness, bracing pattern, and more — would all have a much larger effect on the sound.
What Finishes Are Used On Guitars?
As I noted above, the two most common kinds of finishes used on modern guitars are nitrocellulose lacquer and polyurethane.
In broad terms, more expensive guitars use nitrocellulose, often referred to simply as nitro, while less expensive ones use polyurethane, which is sometimes shortened to poly.
If you go by what you can read on some forums and blogs, nitrocellulose is always superior. And there is something of a case to be made for that, but as you might expect, that isn’t the whole story.
The argument for nitrocellulose lacquer over polyurethane is that nitrocellulose lacquer is applied in far thinner coats, and therefore the final finish is thinner and does less to dampen vibrations. Some people argue that the chemical composition also allows for more vibration, but the thickness of the coat is the most commonly cited advantage.
And that is true. Nitro definitely leaves a thinner coat than poly, and the cracks and checks you see on older finishes speak to it perhaps doing less to inhibit the vibration of the wood.
There’s more to it than that, however. The reason for the cracks and checks in older nitrocellulose lacquer finishes has more to do with exposure to air and age than the properties of vibration.
Polyurethane finishes are thicker, but the reason they don’t crack has more to do with the fact they don’t degrade in the same way as nitro finishes do. Some people find the weathered look of an old — or artificially aged — aesthetically pleasing, but don’t let that make you think such finishes are automatically better or that polyurethane finishes sound worse in some way.
In fact, if you took two guitar bodies and finished one in nitro and the other in poly, and switched pickups between them, you’d likely have a very hard time hearing the difference.
One way you know that’s true is the fact Eddie Van Halen’s “Frankenstrat” was painted using basic spray paint, and no one has ever said that guitar’s tone suffered because of it.
Older acoustic guitars, and some modern ones made by boutique luthiers, don’t use nitrocellulose lacquer or polyurethane for a finish. Instead, they use a much older kind of finish — shellac.
Made from the shells of insects, shellac has been used for centuries as a finish for stringed instruments like violins. It was commonly used to finish acoustic guitars into the early 20th century.
Shellac offers a much, much thinner, and more delicate coating than even nitrocellulose lacquer does. This video looks at French polishing, which is a traditional technique that uses shellac to create a multi-coat finish.
So if thinner finishes sound better, why isn’t shellac used more?
There are a few reasons makers use nitro and poly more, but durability is the main one. Cost is the other factor.
Shellac is generally applied as shown in the video above, with multiple, hand-rubbed coats. Nitrocellulose and polyurethane can both be sprayed on, and that process can even be automated.
And the durability, especially of polyurethane, is something some players, and many makers, actually prefer.
Many players, and many people buying a guitar for someone else to play want a guitar with a finish that looks nice and clean, and makers want a finish that is durable enough to stand up to being used.
The thick coating and the fact it’s heat cured and therefore quite durable makes a poly finish quite appealing for a lot of people.
As I just looked at, there are advantages and disadvantages to any kind of finish. Shellac has to be put on by hand and isn’t as durable as other finishes.
Nitrocellulose lacquer is thicker than shellac and can be sprayed on, either by hand or with an automated system, and some players prefer it for aesthetic reasons. It’s not as durable as a polyurethane finish, however.
The thicker polyurethane might have a slight impact on the sound a guitar produces, but it is far less likely to crack and check, and people who like new-looking guitars will appreciate how durable it can be.
When it comes to finishing a guitar, just like any other part of guitar building, there are going to be compromises. Some finishes might slightly affect the tone of the instrument, but in exchange might offer some other kind of benefit, from durability to scratch resistance.
Figuring out what balance you want is how to find the right finish for your next guitar.
I’ve been a musician, particularly a guitarist, for more than 25 years. I love writing about guitars, gear, recording, music in general and more.