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Re: Patina Questions

Author: L. Omar Henderson
Date: 2006-11-22 18:11

Excellent post Terry.

The process of vulcaniztion is cross-linking the long monomer stands. Early vulcanization processes were hampered by sub-optimal catalysts - primarily sulphur and raw materials tainted with contaniments e.g. plant protein, metals, etc. that modified the cross-linking patterns. The quality of raw rubber resin improved dramatically within the last 20 years because of the need for a higher quality starting material for latex gloves. Older rubber plantations have given way to more modern rubber farming techniques. The older machinery used, variable timing and temperature regimes, all contributed to variable end products in the chronology of vulcanized rubber manufacture. Tempering, heating cycles also helped produce a better product. Many of the manufacturing and tempering details of manufacture of older rubber mouthpieces have been lost or really not reproducable with todays machinery and raw materials but with modern technology the cross-linking signatures of old vulcanized rubber can be determined and perhaps close approximations of these signatures (but not the original) can be duplicated. We can only duplicate the rubber in its condition today - certain conditions of trace materials also cannot be duplicated. Do we know if this actually makes a difference in sound qualities??? - your guess is as good a mine !!!

Vulcanized rubber will begin to degrade - breaking cross-links - immediately after manufacture. This process to degradation may take many years but is accelerated by environmental conditions such as UV radiation, oxygen and ozone, and air pollution. The surface of course is more prone to degradation and various batches of rubber-mouthpieces may react differently based on the amount of vulcanization and presence of excess sulfur (the earliest catalyst used) which migrate to the surface and form colored sulfur compounds which many refer to a patina. These sulfur compounds are very stable chemically and actually help reduce further surface degradation and migration of catalyst to the surface.
L. Omar Henderson

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