In this building, workers made the clay crucibles known as pots, whose manufacture was the most exacting work in the glass-making industry. About two inches thick, thirty inches high, and forty inches wide, each pot could hold 1500 pounds of molten glass and could cost as much as $100 in nineteenth-century dollars to produce. Because any flaw could cause a pot to crack and spill melted glass inside the furnace, pot manufacture was done with fastidious care; such a failure required the furnace to be slaked, shut down production, and set a dozen men to labor for hours to remove the broken pot. Preferred clay was imported from St. Louis, Missouri, Germany, or England, though some South Jersey factories used clay from Newcastle, Delaware. After forming, the moist clay pots were dried for from two months to a year. A few days before use, a pot was moved to an area of the Melting Furnace, probably on the west side nearest the Pot House, for preheating, first in the side room of the Melting Furnace to between 80 and 100 degrees, then in a separate small furnace called the Pot Arch until it reached the temperature of the main furnace, after which it was moved into the main furnace and the furnace was resealed. Window glass was made from a mixture of silica sand, lime, and potash recovered from the furnace; these raw materials, called a batch, were dumped into the pot through a small hole in the front of the furnace, which was then temporarily plugged, and left to melt for about twenty-four hours. The intense heat gave a pot an average productive life of seven weeks.