Epoxy clay refers to a group of room-temperature-hardening substances used as sculpting compounds and adhesives. Exact compositions vary according to manufacturer and application. They are stored until use as two components of clay-like consistency. Kneading the two components into each other creates an exothermic chemical reaction that activates the substance for use and curing. Unlike many other types of glues, an epoxy adhesives can fill gaps and even be molded into a structural part or sculpture.