BVC Glass

Thermal Expansion The graph shows the thermal expansion, in parts per million (PPM) per degree Celsius of plate glass, BVC glass, and borosilicate glass (Pyrex®).  Plate glass = 10 PPM/ºC BVC glass = 2.8 - 2.4 PPM/ºC Borosilicate = 3.2 PPM/ºC       Heat conductance The ability for the material to adapt to ambient temperatures is important. Different types of glass will take different times to adapt. When the heat conductance is rapid , it has the tendency to deform less during the process (because there is less resistance between the center and the edge of the blank).     Glass hardness This graph shows the differences of hardness for each of the three materials; plate glass, borosilicate and BVC glass. Grinding and polishing times for BVC glass will be roughly 1.4 times faster than for plate glass and about 3 times faster than for borosilicate.     Glass reflectivity This graph show the reflectivity of Plate glass, Borosilicate glass and BVC glass.  When testing the mirror with a Foucault tester, the reflectivity is an important property.  Also, it is easier when checking for a pit hole and a potential scratch, you do not need to scan the blank with a magnifying glass, the defect created by the abrasive will be gray on a black background.