The material is known generically as hard rubber. The sulfur percentage, the percentage of other additives and the applied temperatures and duration during vulcanizing are the main variables that determine the technical properties of the hard rubber polysulfide elastomer.”
Thus there is a infinite variety of ebonite or hard rubber compounds, tweaked for specific characteristics. I think some high end bowling balls are made of ebonite, as are smoking pipe stems and other things.
The Otto Link mouthpiece boxes refer to “Eburnated” hard rubber.
Here is a long article about the Otto Link Eburnated hard rubber:
Here is an interesting article about old french mouthpieces with some information about the hard rubber used.
The process of manufacture of ebonite/hard rubber is the focus of this old article:
Some mouthpieces, like Drake mouthpieces use RESIN as the material for their mouthpieces. I think he as gone so far as to speak of a “vintage resin”. He is also known for ceramic mouthpieces.
The resin used is a synthetic resin, an artificial formulation of natural plant or tree resin. It is a viscous liquid that can permanently harden. Again, there are many formulations of this.
And perhaps the broadest term of all is “PLASTIC” The word plastic is derived from the Greek, meaning “capable of being shaped or molded” Consequently, I feel that Ebonite and Resin are types of plastic.
The Runyon mouthpieces are made of plastic. Santy Runyon was the designer and owner. This is what the Runyon company says about the plastic:
“Runyon Products believes that quality starts in material selection. For this reason all their mouthpieces are designed around engineering materials, not general purpose ABS plastics and inferior grade metals.
Since good tonal production depends on the vibrations of the mouthpiece as well as those of the reed, the vibration potential (flex modulus) of the mouthpieces is an essential component. Through extensive experimentation, Santy has selected a plastic alloy as the best possible substance for this mouthpiece, a material with the same flex modulus as that of hard rubber. This special alloy is superior to hard rubber in several important aspects. It possesses greater dimensional stability and impact strength. This means that it doesn’t chip as easily; moreover, because it is more resistant to heat, it is also more resistant to warpage.”
I remember reading that much of the ebonite currently comes from a manufacturer in Germany. But many mouthpiece manufacturers order a special formulation that they tend to keep secret. I think many mouthpieces have a certain percentage of ebonite in some sort of base like resin or other “binder”. I do not know. There are some tales of old ground up car tires ending up in Ebonite mouthpieces.
The Mouthpiece Cafe folks said: “The rubber composite we use for our line of mouthpieces was developed with the a goal to contribute to a free-blowing quality and to produce a beautiful resonance.”
Ultimately, I think the shape and geometry of a mouthpiece is by far the largest determiner of how it plays.
Many mouthpiece materials are selected for how easy they are to form and machine, how durable they are and how cost-effective they are.
Mouthpieces made of wood, like ebony, or made out of ivory might be the best natural substance, but impractical.
Ebonite was originally formulated as a substitute for ebony and it has proved itself to be a wonderful material for mouthpieces. This does not preclude other materials from being equally good. Ask a bari sax player using a stainless steel Berg Larsen mouthpiece or a clarinet player using a crystal glass mouthpiece. I wouldn’t be surprised if there are some solid silver, gold or platinum mouthpieces out there.