You're asking too much of the reader here. Such things don't exist in Amerikan society anymore. Gutta percha went into extinction with sal ammoniac, litharge, and lunar caustic. Trying to explain things to an undergraduate is nearly impossible these days. There's no past experience to anchor a concept with.
Chemicals are evil.
People who know about chemicals must be evil, too, and they certainly aren't normal. The result is springy rubber.