The thermal expansion

Shows the thermal expansion

         This 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/ Degree C

   BVC glass = 2.8 - 2.4 PPM/ Degree C

   Borosilicate = 3.2 PPM/ Degree C

Heat conductance

         The ability of the material to adapt to ambient temperatures. Different types of glass will take different time to adapt. When the heat conductance is rapid , it has the tendency to deform less during the process ( because of less resistance between the center and the edge of the blank).

Glass hardness

         This graphic shows the differences among the hardness of 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 graphic show the reflectivity of the Plate glass, the Borosilicate glass and the BVC glass. When testing the mirror with a Foucault tester, the reflectivity is an important property. Also, when checking for a pitt 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.