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
Glass-to-metal seal to the glass which is inside of the bore of a strong metal part with higher coefficient of thermal expansion. Compression seals can withstand extremely high pressures and physical stress such as mechanical and thermal shock. Because glass is extremely strong in compression, compression seals can withstand very high pressures. Silver chloride, which melts at 457 C bonds to glass, metals and other materials and has been used for vacuum seals. Even if it can be a convenient way to seal metal into glass it will not be a true glass to metal seal but rather a combination of a