Gibson Mastertone Banjo

 

The Gibson Mastertone banjo is one of those great success stories; and though it had its occasional failures, the “Mastertone” brand has made it through more than 75 years of hard times and rough service. Today, it is the only surviving representative — still in production — of the turn-of-the-century banjo era; and it is the instrument most highly acclaimed by both bluegrass and dixieland banjoists. While several models were unsuccessful, a major portion of the line won its way to the stages, homes, and hearts of countless musicians.

The Gibson Mastertone has been copied by private luthiers and commercial manufacturers alike. Certain models bring the highest prices from collectors around the world, and for some professional bluegrass banjoists, a Mastertone is the only instrument they will play. For others, the image is so strong that they feel that they are not really rendering a certain music style unless they are doing so on a “Gibson.”

Although several evolutionary design changes were made, the instrument has remained basically the same from about 1938 until 1985. In that year, I worked closely with Gibson and Earl Scruggs to bring back the design styles of the early years — a project which was the foundation of the Earl Scruggs model banjos now produced by Gibson.

The most interesting part of the Gibson banjo history transpired between its inception in October 1918, and a time around 1938 (see Chronology of Gibson Banjos) when, in my opinion, the line went through its greatest evolution. While there were several new model introductions after that period (such as the styles -100, -250, and -800), there is a wonderful story in changes made during those first 20 Golden Years.

At some point in 1917, the company began to work on a simple open-back banjo. The first banjo was announced in a price list dated October 1918. It was a plain tenor model, simply promoted as a “tenor banjo.”

The period of 1918 to 1924 marked a very important era for Gibson. It was a time of greater sensitivity that the company had known before: A time when the likes of such renowned luthierie figures as Lloyd A. Loar, Guy Hart, George D. Laurien, and Lewis A. Williams graced the halls and workbenches at the Gibson Plant in Kalamazoo; a time when great men were forming great ideas; a time when Gibson was to win honor with its finest instruments — the style-5 Master series. These included the Master Model Mandolins (F-5’s), Master Model Mandolas (H-5’s), Master Model Guitars (L-5’s), and the Master Model tenor banjos (TB-5’s) (from which the “Mastertone” name was derived).

Gibson banjos changed drastically during their early stages of development. The first resonators were flat, plate-like discs that covered the back of the pot assembly (body) with half the plate hinged to swing out like a trapdoor. Loar had his hand in developing a floating tone tube with 20 ball-bearing contact points, and a “tuned air chamber.” This was followed by a bolt-on celluloid (Gibson called it “Pyralin”) plate. Finally, in February of 1925, the company announced an all-new banjo. The first had a spring-loaded tone chamber and a full wooden resonator. Variations which grew from this model were to become the standard of excellence for banjos around the world.

The craftsmanship of the earliest Gibson banjos was good, but the construction was nothing more than basic. The first laminated rims had a cavity between the laminates in the upper portion to act as a “tone chamber,” but the head rested directly on rim rendering the tone chamber virtually useless.

George Altermatt's tone chamber patentGeorge Altermatt’s tone chamber patent described the ball-bearing design and tube-and-bracket concepts.









Gibson made great strides with one problem that plagued most banjo makers. Of all instruments in the line, the banjo had the longest and thinnest neck and other makers went through great strides to laminate and fortify the neck to prevent it from warping under string tension. Gibson’s Thaddeus McHugh invented an adjustable truss rod in 1921 that kept Gibson necks straight. Interestingly, however, the patent called for the rod to be installed being lowest in the heel and peghead, with the center of the rod close to the fretboard. While this provided “post tensioning” and kept the necks straight, over-tightening of the truss rod nut would cause the neck to bow backwards. It wasn’t until many years later that Gibson inverted the rod’s curve (with the center of the rod being positioned away from the fretboard inside the neck).

Following are details on models and construction features during this period:

Model designations: The banjo models were given letter codings to indicate the type of stringing: “TB” referred to a tenor banjo, “PB” stood for plectrum banjo, “GB” described a guitar banjo, “MB” was applied to a mandolin banjo, “UB” denoted a ukulele banjo, and “RB” indicated a regular (5-string) banjo. The letters were followed by a number indicating the grade or quality of the instrument: -00 (double zero) was bottom of the line (although there was a short-lived “Jr.” model which was the least expensive); -0 was next; -1 was slightly better, and usually meant nickel plating and plain-colored finish; -11 (double 1) was a later inexpensive version; -2 followed with fancier inlays and extra binding; -3 was fancier; -4 fancier yet; and -5 (for a brief period) was the fanciest model boasting gold plating, choice curly maple, and elaborate inlay designs. Thus a TB-5 was a tenor banjo with -5 grade fancy trimmings. (For more detailed information on the various models, see Banjo Models.)

From 1925 to 1930, several fancy models made their debut; the style -6 with fancy black-and-white binding (or sometimes gold-speckled binding); the TF or Florentine; the TG or Granada; the Bella Voce (which means “beautiful voice” in Italian); and the All American — an elaborate instrument with a carved eagle on the peghead.

Rims: Except for the very first Gibson banjos, all of the rims for this period have been made of steamed, rolled, and laminated maple. Depending on the model, there were constructed of either three or four plies: three plies of 1/4″ maple to make up a 3/4″ rim machined down for one-piece flange models, and four plies of 1/4″ rim to make up the heavy rim used for tube-and-plate models. All of the laminates were taper-cut, a method of angling the joining ends of each laminate so that they would overlap rather than have a flat end-to-end joint.

To the inexperienced observer, some rims appear to have been made of five thinner plies; but this is a misconception caused by a practice still in use today. The bending and lamination process is a difficult one and several rims might come off the mold with unsightly glue joints. To improve the cosmetic appearance, a poorly glued three-ply rim would be placed on a lathe and a “cut” made into the glue joints. Then, thin filler strips would be glued into the cuts and then machined flush, resulting in a multiply appearance, while still basically a solid three-ply construction.

One-piece flange models required that the rim be machined down so that the flange could slip over the rim, and thus the rim had thin walls approx 1/2″ thick. The tube-and-plate models required an added lip to support the tube and did not require machining down of the rim, leaving the tube and plate rims to be a full 3/4″ thick.

Flanges: The tube was the first non-shoe system used by Gibson to secure the tension hooks (that tighten the head). As with later models, the tube was secured against a lip on the rim. By acting as a tight band around the rim, the tube also added greater structural integrity than competing bracket and shoe models. At the first introduction of the full resonator models, a stamped “plate” was added beneath the tube to fill the opening between the rim and the lip of the resonator. This plate had stamped perforations around its surface. At one point, the lesser models had hex-shaped “diamond” openings in the flange compared to the classic Mastertone crescent/arch opening with rounded ends. To secure the pot assembly to the resonator, the earliest models used small hex-head screws that went through a hole the flange to a lug in the resonator. This was later changed to the same hex-head screw going through a separate bracket below the plate that was attached to the rim, and still later to a serrated thumbscrew replacing the hex-head screw.

Coordinator rods: One of Gibson’s long lasting developments for attaching the neck to the rim was the “coordinator rod” system; two brass rods that attached to two screws in the heel of the banjo neck. The rods secured the neck to the rim and provided a means for correcting the “action” (height of strings above the fretboard). By selectively tightening the nuts at the tailpiece-end of the rods, the angle of the neck could be changed to adjust the neck’s angle. Gibson’s first banjos had a nut on the top neck screw and only one rod on the lower neck screw. The earliest banjos with the double-rod coordinator rod sytem had one lag screw threaded into the neck and one “L”-shaped lag screw embedded into the bottom of the neck’s heel (these lower screws are permanently glued in and can not be removed). (Banjos with embedded lower screws also had an separate heel cap (wooden piece) covering the bottom of the neck heel.)

Tone chambers: The “tone chamber” was a cast ring that sat on top of the wood rim to add rigidity and mass to the “pot assembly” (banjo’s body) and enhance the vibrations of the (then) skin head. Several variations were created by Gibson, and these can be followed in my web page on the Evolution of Gibson Banjo Rims. It has been thought that the spring-loaded “ball bearing” tone chamber was designed to counter the effects of weather changes on the skin heads. This is not true, especially since any vertical change in the head’s position would cause improper playing action. The springs were employed to improve the resilience (springiness) of the tone chamber. The ball bearing tone chamber design is attributed to Lloyd Loar.

Woods: Each of the model designations indicated a particular species of wood used for that model (see Banjo Model Features, below). The lower numbers indicated that plain maple was used with a colored finish such as “dark mahogany” stain used over maple. Curly maple, burl walnut, and Honduras mahogany were available on their respective models. Other woods such as white holly, were available on fancy models like the Florentine and Bella Voce. In all cases, the rims were made of maple, and the majority of fretboards were made of Brazilian rosewood (not ebony as commonly believed). Only the pre-1925 (trapdoor period) and style -6 banjos had ebony fretboards. Except for the earliest models, all of the banjos made from 1925 to 1935 (in fact, until around 1969) had one-piece necks (however, pegheads were fitted with laminated “ears” to give them the necessary width, and the earliest models had a veneer over the back of the peghead to cover up the ear’s glue joints).

Banjo serial numbers: During the 1920s, Gibson instruments were made in lots of 40s (for the most part, this procedure continues today). The bins that were used to move instruments from department to department had 40 cubbyholes. An entire bin was a “lot” and would contain instruments of the same model. Sometimes, two or three bins or lots of the same model would be made at one time. To assure that parts would fit together and that the finish color would match, the serial number of each banjo was stamped inside its rim, penciled on the neck heel, and chalked or painted in white or red on the inside surface of the resonator (with red numbers most often being painted along the inner edge of the resonator so they could be read through the holes in the plate or flange, yet the red would not be obvious from a distance).

The number was in two parts: first a four-digit number to indicate the factory order number or lot number, and then a second series (usually two digits) to designate that particular banjo within the lot. Banjos made prior to February 1925 were numbered in the 11,000s. With the introduction of the new full-resonator models in February 1925, a new prefix was assigned to the banjo line, beginning with 8,000. Around 1935, when the series reached the 9,900s, it was again changed to a whole variety of numbers whose dates have been difficult to document or verify. Although each new year did not precisely mark a change in the numbering system, the following chart will serve as a close guide to Gibson’s early serial numbers (for banjos) and their approximate date:

1925…..#8,000 1928…..#8,800 1931…..#9,400 1934…..#9,800
1926…..#8,350 1929…..#9,000 1932…..#9,600 1935…..#9,900
1927…..#8,600 1930…..#9,200 1933…..#9,700 1936…..various

Platings: Instruments were offered in three basic plating finishes; nickel, chrome (them called “chromium”), and gold. The gold plating was often referred to as “triple-gold plating” — a description of the length of time pieces were left in the plating bath (and not an indication that three separate plating processes were done). Some of the gold-plated models were “Florentined,” a burnishing technique that dulled the plated surface to produce a matte background.

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