The streaks produced by ordinary glass are mainly caused by uneven batch materials; corrosion of refractory materials (mainly introducing Al); and agitation during the manufacture of glass products.
Therefore, optical glass should be started from these aspects. The raw materials require purity >99%, impurities are less than a few hundred thousandths, and the particle size and weighing of raw materials have high requirements. All furnaces use ceramic or platinum as refractory. Molding generally only uses the casting method, rolling method, broken cylinder method, and liquid method, which effectively prevents the glass from being stirred during molding.
In addition, the structure of the furnace is also different from the daily glass furnace. It is divided into a melting tank (feeding), a regulating tank (adjusting the melting atmosphere), a refining tank (clarification), and a homogenizing tank (stirring). The daily output of large furnaces is generally Only 5 tons.