Epoxy

by Paul Jacobson

Originally published in Guild of American Luthiers Data Sheet #90, 1978 and Big Red Book of American Lutherie Volume One, 2000



For the contemporary luthier, epoxy opens up an entire realm of innovative techniques never before possible. It can be more than a mere substitute for earlier, less satisfactory materials; it can make way for totally new design concepts in the luthier’s art.

Epoxy is so different from any material used in the past by luthiers that it requires a whole new set of assumptions about application possibilities and handling techniques. Many luthiers who have had any experience at all with epoxy think of it as merely a kind of glue and may substitute it on occasion for Elmer’s. To be sure, epoxy is an excellent adhesive, but to think of it as just glue is to have a limited concept of its basic properties and its vast potential in lutherie.

Epoxy, the Material. Epoxy is one of a group of chemicals known as thermoset plastics in which change from liquid to solid occurs by endothermic chemical reaction rather than ectothermic hardening or volatilization of a solvent. The reaction is nonreversible; epoxy, once hardened, cannot be melted with heat or dissolved in any solvent. Heat of 150°F or higher will soften it slightly, but as the heat increases the epoxy undergoes molecular deterioration rather than melting and tends to turn crumbly.