Warm glass or kiln-formed glass is the working of glass, usually for artistic purposes, by heating it in a kiln. The processes used depend on the temperature reached and range from fusing and slumping to casting.
"Warm glass" is in contrast to the many cold-working glass processes, such as leaded glass. "Hot glass", glassblowing, or lampworking is the working of glass in a direct flame, such as for laboratory glassware and beadmaking.