Although not really “carving”, kiln-carving is a technique that gives creates the appearance that part of the glass surface has been carved away.
The basic process is simple: cut pieces of fiber paper are arranged on a kiln shelf (usually on a larger base piece of fiber paper) under a piece of glass. When fired, the glass settles into the spaces between the fiber paper pieces.
Once cooled, the glass is turned over revealing recesses created by the fiber paper design elements.
Kiln carving works best when the glass is at least 6mm thick.
The temperature will determine how “crisp” the design relief on the glass – the hotter and/or longer the glass is fired the finer the detail that will be visible in the glass.