Fourcault process the pit must be "heated back" and then the process can continue anew. Glass chemistry has a huge impact on the process since it controls the melting, forming and annealing temperatures, liquidus temperature (point where various chemicals that make up the glass start to crystallize out of the glass) and rates of change of characteristics of the glass itself. Occasionally the ribbon will break or crack, leading to failure of the drawing process. Such breaks, known as "checks" can be alleviated by using proper operating parameters. Sometimes an expedient measure, using a portable source of heat, can be used to
History of glass in sub-Saharan Africa be shaped, heated and cooled. The archaeological evidence of beadworking in Sub-Saharan Africa provides examples of both types.5 9 With melted glass working, beads found were generally formed by either a wound, drawn or moulded process. Wound glass beads, also known as Tubular, Cylindrical, Spherical or Melon-Shaped, were formed by folding molten glass around a metal rod called a mandrel. Once the glass had cooled slightly, the material was slipped off the mandrel and pinched and prodded until it reached a desired shape.9 Also known as Cane beads, Drawn beads were formed by dipping an iron blowpipe into molten glass