Hard Paper Insulators

1916 Scientific American  
This latter point would suggest that in bubble-free . glass there is a greater possibility for cases of want of homogeneity to occur-a point that is worthy of con sideration. Striae (Veins).-This defect is produced during the melting operation, and is the cause which necessitates the rejection of the major portion of the glass made. The two terms are used to describe the same defect, although the term "veins" is generally reserved to describe heavy strire. The most important source of strire is
more » ... source of strire is the action of the fluid glass on the fireclay pot during melting, being threads rich in silicate of alumina, although volatilization of certain materials during the time the glass is main tained at a high temperature is a contributing source. Borate glasses are prone to carry strire as boric acid is freely volatilized from glasses which contain it. This loss of a constituent at a particular point produces layers of sliglitly varying refraction, which can only be over come and completely incorporated by stirri ng.
doi:10.1038/scientificamerican02051916-87bsupp fatcat:p6vtgrwtb5br3i7zerkuvvl5sq