Epoxies are the most versatile of all the adhesives, providing excellent adhesion to both porous and nonporous materials, including metals. They harden by chemical action and so can be made without solvents. When used without solvents they shrink only slightly on hardening which is useful for bonding poorly fitted joints. Epoxies are very moisture resistant and the bond strength is good up to about 350 degrees Fahrenheit.
Epoxies are usually binary or two part compounds, the resin and a catalyst or hardener, which are mixed together just prior to use and which harden rapidly. Formulations meant to be used at room temperature must be used within a short time after mixing, often within a half hour or less; this is the “pot life.” Formulations that require heat to complete their cure may be kept at room temperature for days or months before hardening but will set very rapidly if heated. The resin can be modified to cure hard or with slight flexibility, which would be a drawback if used in the body or paws of a costume.