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The Life Cycle of a Reed
by James Kopp
It is a truism among bassoonists that even good reeds change over time, from youth to middle age to old age. We are now in a position to ask what chemical and physical changes are at work in this aging process.
About 20-24% of Arundo donax tissue is hemicellulose (various types, but primarily AMGX), the purpose of which is to aid in absorption of water in the living plant. Even in the dead tissue of the bassoon reed, it continues this function. Casadonte reported that the “breaking-in” process for the clarinet reed is largely a matter of the leaching out of AMGX – which has a slightly sweet taste – through repeated use of the reed.
As the reed is played upon, the sweet taste gradually diminishes, and the reed becomes gradually less hydrophilic, until some stable point is reached. This is the point at which the reed is generally said to be “broken in.” These effects are probably due to the loss of hemicellulose in the reed cell wall matrix….32
As the reed continues to age, (1) the loss of AMGX continues. Two other types of chemical breakdown occur:
(2) [C]ontamination of the reed due to salival artifact (amines, glycoproteins, sialic acid, etc.). These breakdown pathways render the material, in effect, more brittle and less hydrophilic…. (3) [S]aliva contains ammonia and other alkali, and these have been shown to induce plasticization [softening] in wood. The result is that the modulus of the material falls (the reed becomes “softer”), and the damping increases (the reed does not maintain sound easily).33
Other factors in the aging process are physical rather than chemical. Casadonte reported that contamination by saliva and oral microflora causes an increase in the mass of the reed’s blades. Casadonte also identified another bacterium strain that adds mass to the clarinet reed’s tip, changes its shape, and reduces its range of motion.34
Unlike the hemicellulose AMGX, lignin does not leach out of the bassoon reed. In fact, lignin is hydrophobic, or water repelling.35 Nor does reed use cause lignin to break down through mechanical faults like cracking and tearing. In this sense, the reed does not simply “wear out,” as Casadonte explained.36
Bassoon reeds are subject to additional types of degradation. Even before the chemical aging process renders a bassoon reed undependable, the reed will suffer from a gradual closing of the tip aperture over time. This is probably due to two factors. One is a gradual deformation called mechano-sorptive creep. Because lignin is amorphous (fluid), it does not always make a perfect recovery from the swelling that results from hydration. Instead, some deformation due to swelling remains, which Casadonte termed mechano-sorptive creep.37
The second is a gradual loss of wet tension, as explained above. This is correctable through wire adjustments, but only partially so. A reed that absorbs less water expands less. The less absorbent blades swell less upon hydration, so that the tip aperture, under reduced wet tension, opens less. In addition, the brass wires lose their original tautness, so that they no longer exert proper pressure on the tip aperture. The player usually re-adjusts the tip aperture by tautening and compressing the wires. This adjustment helps extend the reed’s useful life, but the reed may become less dependable in speech, due to the player’s decreasing control over the tip aperture.
Various chemical remedies to the problem of reed aging have been suggested. Casadonte suggested two new possibilities: (1) a water-based antibacterial rinse (currently available by prescription only), and (2) gas phase infiltration with parylene, a particularly inert polymer.38 Ron L. Fox suggested a treatment based on cross-linking of cellulosic chains to render the cane bio-resistant and wet stable, which improves enzymatic degradation.39 A commercially available product called ReedLife is recommended for clarinet and saxophone reeds; its chemical basis and preservation strategy are unknown.
32. Casadonte, 168.
33. Casadonte, 233.
34. Casadonte, 233, 238.
35. Casadonte, 106.
36. Casadonte, 232.
37. Casadonte, 252, 256.