6. Other Properties

6.1 Bubbles and Inclusions

It is most desirable to manufacture bubble-free optical glass, but the existence of bubbles to some extent is inevitable. Bubbles in optical glass vary in size and number from one glass to another due to the many different compositions and production methods utilized. The classification of bubble content is established by specifying in mm² the total bubble cross section existing in 100 ml of glass volume. Inclusions such as small stones or crystals are treated as bubbles. Our five bubble classes are shown in table 10. Our classification includes all bubbles and inclusions measuring larger than 0.03 mm.