The melting furnace was the heart of the glassworks, where silica sand, lime, and potash were melted into glass at a furnace centered in the building. Before use, wood was dried and stored in the northeast corner, and men in stoke pits below floor level on the east and west sides fed the intense fire, whose draft was powerful enough that a glassblower at a plant in Clayton recalled a sandwich being pulled from a man's hands and up the chimney. The raw materials had to be prepared before mixing: sand was dried and heated in sand kilns, probably in the southeast corner of the building; lime was prepared in the lime kiln south of the Flattening House; and potash was removed from the furnace after firings and stored until needed. These materials were mixed into a batch and melted in pots set on the masonry platform above the fire, called the siege. Wooden platforms called benches on the north and south sides gave access to the molten glass and provided elevated work stations for the glassblowers. Glassblowing was a team effort requiring speed, coordination, skill, and strength. The gatherer began by thrusting a 5 foot long, 30 pound iron blowpipe into the furnace to collect a 50 to 70 pound glob of melted glass called metal, protected from the heat only by a wooden mask with eye slits fitted with blue or amber glass and held in place by a mouthpiece gripped with his teeth. He fanned the molten glass into a solid cylinder with a wooden mold and handed the blowpipe to the glassblower, or gaffer. These master craftsmen needed the strength to handle 100 pounds of blowpipe and molten glass and the skill to form the glob into a cylinder ten inches across and five feet long, with sides a uniform thickness of 1/8 inch, within five to ten minutes. Standing on the elevated bench over a swing pit about three feet below floor level, they shaped the cylinder by blowing through the pipe and swinging it to lengthen the glass through centrifugal force. Some chained themselves to posts to counter the weight, while others rejected such precautions and sometimes lost their balance, falling into the swing pit covered with hot, broken glass. Once the cylinder walls reached a uniform thickness, it was removed from the blowpipe for annealing and flattening. Window glass cylinder blowers were regarded as the masters of glassblowing, and they were paid not by the number of cylinders they made but by how many boxes of usable glass could be cut from them, receiving no compensation for imperfections or thicknesses out of tolerance.