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Heat Pressing

Heat Pressing

by Leo Bidne

Originally published as Guild of American Luthiers Data Sheet #43, 1977



Heat pressing is the art of forming wood to a new and permanent shape with heat and pressure. With practice, it is an effective method of action adjustment when extreme measures are necessary; when time or poor construction methods develop a problem, has a fair idea of what a “good” action is, and is familiar with such terms as “action”, “buzzing”, “truss rod”, and the numbering system of frets, etc. The term “buzzing” assumes that the string is plucked moderately hard. Applied to guitars, the art of heat pressing is to create the optimum neck shape for a fretted, plucked string. This means a buzz-free, even action over the entire length of the fretboard. Part One explains what that neck shape is, clears up some of the fallacies and old wives’ tales on the subject, and points out some common neck problems.


The Bow

Basically, a plucked string travels in a bow, like this:

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Pearly Shells and Nichols

Pearly Shells and Nichols

by David Nichols

from his 1984 GAL Convention lecture

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



My shop recently did two guitars for the Martin Company which are elaborate enough that they encompass basically all the different techniques used in pearl inlay. We inlaid the tortoise shell pickguards, the rosewood headstocks, ebony fingerboards, and all edgebinding. I photographed many steps in this process, and we can look at these as examples.

Here’s a picture of where I’m going to cut the pearl and do the inlay work (Photo 1). I have taken an extra liberty with our cutting board, drilling a series of holes in the back where I can stand all the little Dremel attachments that I’m going to need. When we cut pearl, it is either filed, or ground with the Dremel to an exacting contour after we saw it. It gives you a much better looking job if you touch up the sawn edges of the pieces before you put them in.

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Repairing the Sitar

Repairing the Sitar

by Dave Schneider

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



The sitar is a member of the plucked lute family of Indian instruments known generally as vina. The name sitar is from a Persian word meaning “three strings.” The first sitars had three strings which gradually increased to seven. Sympathetic (taraf) strings were added later. The modern sitar has from eleven to thirteen sympathetic strings. An upper resonating gourd, usually attached underneath the nut, is common on most sitars today. The standard number of frets is 19, although Ravi Shankar has added a 20th fret at the top of the sitar for increased virtuosity.

Teak is the wood most often used to construct sitars. The bridges for the main strings and taraf strings, which produce the characteristic buzzing sound of the sitar known as jawari, are made from bone and teak.

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Questions: Martin Finish

Questions: Martin finish

by Walter Carter

Originally published in American Lutherie #104, 2010



Kerry Char from Portland, Oregon asks:

Exactly what kind of finish were Gibson and Martin using before they switched to nitrocellulose lacquer? How was it applied, and when was the switch. I’m thinking that it was oil varnish similar to violin varnish, because it is resistant to acetone. But if that’s the case, how did Gibson do some of their sunbursts? I know that the earlier ones were rubbed, but later ones from the ’20s and ’30s look sprayed.


Walter Carter from Nashville, Tennessee replies:

Neither Gibson nor Martin made an across-the-line change from varnish to lacquer. Richard Johnston and Dick Boak note in their recent book, Martin Guitars: A Technical Reference, that Martin finishes were French polish (shellac) until 1918, when they began experimenting with different combinations of varnish and lacquer. Martin first used nitrocellulose lacquer in 1926, and by 1929 it was the standard finish on most Martin guitars. For Gibsons, Stephen Gilchrist offers this information:

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Questions: Gluing in India

Questions: Gluing in India

by Dale Zimmerman

Originally published in American Lutherie #103, 2010

 

George Mathai from Kerala, India asks:

My friend is a luthier based in the southern state of India, Kerala. For gluing the various parts and braces for his guitars and violins he uses Franklin Titebond glue and Behlen ground hide glue. However, in one of his custom-made flamenco guitars, a rattling sound brought the guitar back to the shop. One of the right fan braces had come off a bit and this was causing the rattling. For that guitar he had used the hide glue to glue the braces on. Kerala is well within the humid equatorial tropics and perhaps the humidity affected the gluing. What is the best glue that can be used to withstand high humidity?


Dale Zimmerman from Franklin International in Columbus, Ohio
responds:

Hide glues such as our ready-to-use Titebond Liquid Hide Glue and most hot-pot hide glues are, and remain, quite sensitive to moisture. That affinity for moisture means that they tend to absorb water when exposed to high humidity or damp conditions, and that increase in moisture causes them to swell and weaken. Bonds that are not subject to stress may show little effect, as the glue loses that moisture and regains its strength as it returns to its original dry state. Where the bond is under stress, however, that stress is likely to cause some opening of the joint while the glue is softened. Ultimately then, the amount of change in a bond over time will be influenced by the concentration and duration of the moisture to which it is exposed and the stress, both inherent in the bond and that created as the wood involved changes in dimension in response to those changes in moisture content.

That means that hide glues are generally considered a poor choice for bonds that are likely to be exposed to particularly humid conditions, especially those that are expected to be under meaningful stress. For such situations, yellow glues, which show little effect from dampness or elevated humidity are a decidedly better choice. ◆