the apparatus performs a forced reshaping of a flat green glass part during a ceramicizing process in which the viscosity of the glass is temporarily lowered due to crystallization heat . the apparatus includes a continuous furnace for the ceramicizing process : a reshaping device provided with activating openings ; and vertically movable pressure - operated reshaping tools arranged in the reshaping device . the furnace is provided with lateral openings for temporarily connecting activating lines to the activating openings of the reshaping device in a sealed manner in order to operate the reshaping tools by supplying pressurized air to the reshaping device or by producing a low pressure in the reshaping device .