In over 40 years as a craftsman I have had a wide range of experience working with different types of wood. Having had the good fortune of studying woodworking with James Krenov helped me to understand the wide variety of characteristics, the potential for graphics, as well as the practical aspects of working with wood. This education enabled me to relate to the material and taught me how to use it to enhance what I was trying to do. This experience has helped me greatly with guitar building. The selection of your wood guitar wood will determine the quality of your guitar.
Without a doubt the guitar wood is the the single most important ingredient in making a great guitar. The more you know about the wood you use, the better choices you will make.
The wood is the reason the instrument sounds the way it does. Acoustic properties of wood vary from species to species, and from tree to tree. It is your task as a guitar builder to know what wood will work for you and your guitar design. This section will provide some important information about guitar wood and its properties.
The Effects of Moisture on Guitar Wood
Humidity changes in the environment greatly effect the wood. The photo on the right shows what happens when a piece of guitar wood has had one face exposed to humidity. I wiped some water on the top face of one half of a soundboard. The face with the water expands across its width but the bottom face that wasn’t does not. This results in cupping.
All wood should be stacked properly so that all surfaces of any wood in the pile are exposed to the air. To do this place narrow sticks underneath every piece creating air space between the piece beneath. This way all the surfaces of all the pieces are exposed to the same humidity level. And if they were cut properly from the start they should remain flat until use.
Humidity and Dimensional Changes in Wood
With increases in humidity the width of a piece of wood will increase because the fibers in the wood absorb water from the air and expand. This expansion is negligible in thickness and length but not so across the width. The wider the piece the more the expansion, especially with thin wood.
This can be especially problematic for the top and back. They are 14-15″ wide and only about 2mm thick. Because of the width the top and the back can move considerably with extreme changes in humidity, upwards of 1/4″. Since the wood is so thin this can have serious effects. Checks or cracks can develop as humidity drops drastically as the wood shrinks from loss of moisture. High humidity will result in swelling and the wood will buckle.
Preventing Problems from Humidity Changes in Your Guitar Wood
These changes must be considered beforehand during the design and cannot be ignored. Ignoring the effects of moisture content in the air on your guitar wood can be disastrous. Many a guitar has seen the effects of humidity.
Preventing these problems starts with selecting the right cuts of wood for guitar building. As explained in the page on cuts of wood quarter sawn wood minimizes wood movement laterally with humidity changes. Braces also help to minimize the effects of humidity. Both the top and the back are braced inside the guitar. This adds strength and stability. Braces that run across the face will serve to keep the plate from cracking. If you notice tops and backs rarely crack under these braces unless they are caused by impact.
Storing Your Guitar Wood Properly
The key to optimal guitar building is stable wood. For the wood to be stable both faces need to be in contact with the air. The video below demonstrates a way to stack your wood and get air to both faces.
Weed out Wood Prone to Twisting or Warping
Some wood is prone to twisting or warping. Possible reasons are because of the way the tree grew, the way it was cut, or both. And there is no way to stop wood from warping or twisting if that is what it wants to do. I have seen builders use weights, straps and bungie cords thinking that this will stop their wood from twisting. Good luck with that. Its not going to happen. The best you can do is either use it in the fireplace or use it for something that is not critical. This wood may be used in some cases such as if you only need a very short piece this wood may do since its twist or warp will be negligible over a short distance. Do not use twisted or warped wood for any of your critical guitar wood such as a neck, bridge, top, back or sides. You will just be asking for trouble.
Additional Topics In this Section
Cuts of Wood
Learn how wood is cut from the tree to be used for lumber. The way it is cut determines many things. There are three basic cuts of wood. Identifying these will enable you to find the right cut of wood for your guitar. Learn how to identify the different cuts of wood and how they are used…
There is no question that the soundboard has more to do with sound production than any other part of the instrument. To make a great sounding guitar it all starts with selecting a great piece of wood for the top. Learn what to look for in picking out a top as well as some misconceptions regarding some characteristics…
Backs and Sides
The back and sides of a guitar can really add beauty to the instrument. But they must be the right cut and have characteristics that will make them a good choice for your guitar. Learn about wood used for guitar backs and sides as well as what to avoid…
The neck may be the most important piece of wood on the guitar structurally speaking. The neck must sand up to the tension of the strings over time and still function as it should. Choosing a neck blank is paramount to having an instrument stand the test of time. Learn about the types of wood typically used for guitar necks and how to identify the right cut to avoid problems…
The primary purpose of braces is to add structural integrity to the instrument. They also add the ability for a narrow range of tuning. Once again choosing the right type and cut of wood is paramount in maximizing both of these things. Learn what types of wood make the best braces and how to select the right cut…
Although the details do not have a whole lot to do with the sound of the instrument, if used properly they can create a stunning visual impact and therefore an added appeal. Coming up with a design scheme that works requires some knowledge of basic design concepts as well as the limitations of the wood you are working with. Learn how to make good choices for your guitars details and more…