Slumping is a categorical description of an area of techniques for the forming of glass by applying heat to the point where the glass becomes plastic. The increasing fluidity of the glass with temperature causes the glass to 'slump' into the mould under the force of gravity. Technique Glass is most commonly heated in an oven, often using glass in a sheet form and 'slumping' it over a form or into a mold. Molds are generally made of high temperature plaster, clay coated with plaster or another re… (More on Slumping)