Glassblower Constructing A Graded Seal

modern chemically impregnated cathodes. To overcome this limitation, “graded glass” seal technology was developed: a glass with a coefficient of thermal expansion in between that of quartz and tungsten is used to join the two dissimilar materials. The glass has a very high melting point so it can tolerate high temperature cathode processing easily but it is more fragile than traditional solder seal and cannot tolerate much mechanical strain. Furthermore, this type of seal does not easily lend itself to automation: skilled glassblowers individually hand craft graded glass seal lamps.