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Moisture Content

Moisture Content

by Greg Jackson

Originally published as Guild of American Luthiers Data Sheet #296, 1984 and Lutherie Woods and Steel String Guitars, 1997



Equilibrium moisture content (EMC) is the point at which wood is not losing or gaining moisture. This occurs when the wood is in balance with its environment. Since the environment changes from day to day, the EMC normally considered is the average EMC. It is very important to understand that this is a delicate balance between the wood and the environment. EMC is not a universal moisture content (MC) for all conditions. As conditions change, the EMC will also change. The water has a tendency to leave the wood and become airborne moisture, just as does the water in clothes hung out to dry. At the same time the wood has an attraction to water and will tend to absorb any available moisture. Water spilled on unfinished lumber can be observed to soak into the wood. The water in humid air, while not so obvious, is also available to the wood and will sometimes be drawn into the lumber. The two forces — 1) for water to be drawn into the air; 2) for water to be drawn into the wood — are opposing forces. The net effect is to create a balance which is called an equilibrium.

Equilibrium is affected by both humidity and by temperature. As the humidity in the air is increased the wood will gain moisture. If the humidity is lowered the wood will give up water to the air. Higher temperatures will force water into the air while lower temperatures will let the wood gain moisture.

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Letter: Glue, Chemistry, Etc

Letter: Glue, Chemistry, Etc

Originally published in American Lutherie #11, 1987 and Big Red Book of American Lutherie Volume One, 2000



Dear Tim,

The history of your Guild closely parallels the history of the Pyrotechnics Guild International Inc., but your publication and membership are twice the size of ours. Who’d have thought we could find over a thousand folks that roll their own fireworks! The PGII is now the largest fireworks organization in history and we have more pros than the pro organization. Come to our convention, I promise you the best fireworks on planet earth and enough of them. It’s a lot of blasts.

Due to back and neck injury, what is left of me has taken up violin making. Until August 14th last year I had quite a laboratory at home, doing research on varnish and wood treatment. The house burned down — gone.

It’s easy to distract an old chemist with ancient chemical puzzles. For the last two years I had made hundreds of these funny organic polyester blends that form glass structure polymers that are traditionally called natural resin and oil varnishes. I played with everything from boil your own sink oil to road paint phenolics, phthalic ester resins, and isophthalatics, and had spent a fortunes on resins and oils in a shotgun approach to educating myself on phytochemistry and what to preserve and pretty up wood with. Fortunately the chemistry is simple, if very complex in the number of products that the four principle reactions can make.

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Basics of Air Resonances

Basics of Air Resonances

by W.D. Allen

Originally published in American Lutherie #1, 1985 and Big Red Book of American Lutherie Volume One, 2000



Stringed musical instruments with soundboxes typical of the guitar and violin families have many internal air resonances. The resonance with the lowest frequency is called the Helmholtz resonance, and its importance to the quality of the instrument is appreciated. The resonances with higher frequencies have been referred to by different names: higher Helmholtz, cavity modes, or standing wave modes. These resonances have been measured and documented for several different instruments, but there seems to be little information on their controlling parameters.

The intent of this article is to give the instrument builder some understanding of the air resonances, what parameters establish the frequencies, and some insight into the potential for using this information to make better instruments. A minimum-math, pictorial approach with approximation and rounded-off numbers will be used. Showing the effects of the controlling parameters is the objective, not the absolute value of a number.

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Area Tuning the Violin

Area Tuning the Violin

by Keith Hill

Originally published as Guild of American Luthiers Data Sheet #283, 1984 and Big Red Book of American Lutherie Volume One, 2000

See also,
Hints for Area Tuning the Violin by Keith Hill



Announcements of “discoveries” of the “secrets” of Stradivarius usually are not worth the ink used to print them. When they appear, everyone reads them with the customary curiosity. Then away they are filed along with the hundreds of other such claims. They get dredged up again when someone writes yet another book on the violin. Mindful of this possible fate, I would like to offer an explanation of a discovery that I have made. It is not of the “secrets” of Stradivarius; rather it is, I believe, the acoustical system utilized by the ancient Italian violin makers.

The system is simplicity itself. It is possible for anyone who understands it and has normal hearing to use it. Moreover, it requires no measuring equipment save the ears and possibly a monochord. Furthermore, the thicknesses and their inexplicable variants, which so annoy our modern sense of decency when we observe them in the finest violins by Stradivari and Guarneri, occur naturally as a result of this system. Because it is so simple, it is, of course, the last place one would think to look for the answer. I expect that once you are equipped with the following information, you will go to your nearest antique Italian fiddle and look to see if what I am saying is actually there.

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Hints for Area Tuning the Violin

Hints for Area Tuning the Violin

by Keith Hill

Originally published in American Lutherie #1, 1985 and Big Red Book of American Lutherie Volume One, 2000

See also,
Area Tuning the Violin by Keith Hill



In my article “Area Tuning the Violin” I presented my discovery of one of the theoretical principles governing the acoustical quality of the violins made by Stradivarius and his numerous Italian contemporaries. Because I believe that the area-tuning principle is the most important of all the acoustical principles pertinent to violin making, I deemed it best to present it in isolation.

I would be less than open with you if I did not say that the American Acoustical Society and the Catgut Acoustical Society both rejected the worthiness of the area-tuning principle. I feel that their reasons were full of vested self-interest. I tell you what I told them: Paying attention to flexibility of free plates is a waste of time and attention. Consider the following points.

First, thousands of violins have been made using this notion for the last century, yet no consistently superior results have been produced.

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This article is part of our premium web content offered to Guild members. To view this and other web articles, join the Guild of American Luthiers. Members also receive 4 annual issues of American Lutherie and get discounts on products. For details, visit the membership page.

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