Article

Woods used in guitar making

Whenever I tell someone I’m a luthier, this question follows up almost every time:

- What woods do you use?

Although many guitar players have some idea of the woods used to build guitars, few know the various species well enough and, most of all, why some are more prevalent than others.

Let’s try to elaborate on the subject.

Stability above all

In each case, whatever part of a guitar a specific wood species will be used for, it must posess great stability. A wood is considered to be “stable” if it will not change shape, or very little, over time.

In the course of its life, a guitar will have to go through different seasons and, often, in different parts of the world. This means it will have to endure temperature and humidity variations. Unfortunately, certain wood species tend to deform greatly when adapting to the surrounding humidity level. Tamarack, besides being much too soft, falls in that category. So, should you find a guitar built with tamarack, don’t ever buy it!

To each function its properties

Of course, most parts of a guitar are made of wood: the neck, the fretboard, the bridge, the top and many more yet. Each requires specific properties and, consequently, different wood species will be selected to fulfill the various functions of each component.

That’s why we will examine the various species used, one component at a time.

The top

The top being no less than the main vibrating “mambrane” of a guitar, it is certainly the component most affected by the wood species selected. Since it must respond as best as possible to the vibration of the strings, it has to be as light as possible. But it must also resist the tension of the strings without deforming or braking. Since this tension can reach anywhere from 65 to 200 lbs (30-90 kg), this aspect is far from negligible. The wood used for the top must therefore be as ridgid AND as light as possible. The most popular wood used for this application is spruce. We are not talking here of the spruce used to build houses but of hundred years old spruce trees found in the cold climates of Alaska and Northern British Columbia, such as Sitka, Engelmann and Lutz spruces. Other European spruce varieties are used, such as Alpine spruce from Switzerland. Western Red Cedar, lighter than spruce, is also a prime choice for classical guitars. Since nylon strings do not exert the same tension as steel strings, the lower rigidity of cedar is less significant. Cedar tops are also found on steel-string guitars but they must be slightly thicker, and therefore heavier, than equivalent spruce tops.

Less traditional woods than spruce and cedar are sometimes used for tops, like Mahogany or Koa for instance, which are hard woods. The main reason to use such woods is, in most cases, essentially aesthetical. Almost invariably, a guitar with a hard wood top will not have as much volume as the same guitar with a spruce or a cedar top.

Of course, there is one last thing to consider which, although subjective, comes into play: the “color” a species will impart to the sound. Some prefer the sound of a spruce-top guitar, others prefer cedar. If you are looking for a specific “color”, your best bet is to trust your ears rather than technical tips from a luthier!

The neck

The requirements for a neck are quite similar to those for a top, but for slightly different reasons. Obviously, it must resist the pull of the strings without bending or twisting and it must be light too. But, in this case, lightness is not needed to improve vibration but simply to produce a well-balanced — rather than a neck-heavy — guitar.

Mahogany seems to meet these criteria very well. Furthermore, its stability is exemplary. Spanish Cedar is also used in classical and flamenco guitars but, in this instance, mostly for traditional reasons. Although Spanish Cedar is often lighter than Mahogany, it is also slightly weaker.

Maple is also commonly used for guitar necks. Although this wood is definitely able to resist the tension of the strings, is affordable and easy to get, I find it too heavy personally.

The fretboard

Since the fretboard has specific functions, the wood species selected must have specific properties too. It must hold the frets in place efficiently but also resist the abrasion of the strings being pushed against it. Over time, this abrasion will cause slight depressions in the fretboard under the strings. Eventually, they will get deep enough to make the guitar sound out of tune. For these reasons, the preferred species are the hardest and densest, such as Ebony or various Rosewoods.

Maple is also used for fretboards, though mostly on electric guitars. However, a maple fretboard needs to be varnished or dirt and sweat will stain it and spoil its color. This is not a problem with Ebony or Rosewood which are darker to start with.

The bridge

The two functions of a bridge are essentially to securely hold the strings in the middle of the top and to properly transfer the vibration of the strings to the top. It must therefore be carved in a very hard wood and, above all, one that rings well. The wood species selected for the bridge must sound a bit like glass when hit. The density of the wood will also play an important role. A denser wood, such as Ebony or Honduran Rosewood, will produce a heavier bridge which will increase bass, while a bridge made out of a less dense wood — Indian Rosewood for instance — will favor highs.

The braces

The braces are the various pieces of wood that can be seen here and there, glued inside the body of a guitar, under the top, on the back, and even on the sides. Depending on their location, they serve different purposes. Generally, the braces strengthen the body, either to resist the tension of the strings (such as the braces of the top) or simply to avoid cracks caused by various hits to the guitar.

In any case, the bracing should not increase significantly the weight of a guitar. That’s why spruce and Western Red Cedar are used almost exclusively, although some braces (mainly back braces) are made in Mahogany or Spanish Cedar.

The back and sides

If there ever was a controversial subject in the acoustic guitar world, it would have to be the impact of the back and sides wood selection on the sound of a guitar. This in itself would deserve to be the subject of a entire article!

If most guitar players and luthiers have long considered the wood of the back and sides to have a significant impact on the sound, more and more are voicing doubts today. According to the latter, the wood selected would only have a minimal impact compared to the quality of the workmanship which would be the determining factor. To prove this point, renowned luthier Robert Benedetto event built a guitar entirely in knotty pine. Of course, the result was worthy of a premium grade guitar.

My opinion lies somewhere in the middle. If indeed I believe the sound quality of a guitar depends on the quality of the luthery work, I still think the nature of the wood used for the back will have a certain impact on the sound. I described the top as being the “main vibrating membrane” of a guitar; that’s because there is a secondary vibrating membrane: the back! Indeed, the back, which vibrates in sympathy with the top, contributes a lot to the richness of the sound. Therefore, the various woods selected for the back will vibrate differently and, by the same token, will have notable influence on the sound.

Three parameters must be considered when evaluating the impact of wood selection on the sound: density, rigidity and sustain.

The denser the wood, the heavier it will be for the same dimensions. Therefore, more energy will be required to make it vibrate as much as a less dense wood. On the other hand, a more rigid wood can be made thinner to vibrate as easily. And a wood with better sustain will vibrate longer after being excited than a wood with less sustain. Obviously, it is very difficult to find the best of the three properties in any one species. So, depending on the sound you are looking for, one species will be more desirable than another.

Let’s take the case of a flamenco guitar. The sound required must be powerful (compared to a classical guitar) and percussive. Sustain is not really an issue because flamenco music rarely calls for sustained notes. That’s why I favor sycamore for this model. A sycomore back will vibrate easily, but the sound will not last. The short sustain, which would be considered an important deficiency on a classical guitar, is in no way a problem here.

I hope you now have a better idea of the reasons why certain species of wood are selected over others in guitar making. However, let’s not forget this is a subject of much controversy and any opinion is constantly challenged by someone. It seems that, no matter what theory you hold true, a luthier somewhere will build a guitar which will put it to pieces! Luthery is indeed a field where beliefs are more prevalent than “real” knowledge, backed by science!

I invite you to have a look at my Wood inventory page. Besides the woods mentioned in this article, you will find there a rich selection of the woods I use to build my guitars.