Weighing and assembly of raw material.
Mixing in the V shaped blender.
Mixed raw material called "batch" is put into a platinum lined pot and melted into amorphous glass.
Glass is stirred to insure good homogeneity.
The pot is removed from the oven after several hours.
The pre-melt is poured into a pan.
After casting, the glass is cooled and crushed. Then the refractive indices are measured for process control.The crushed glass is called "Cullet".
The cullet material shown above is melted again to achieve consistent optical values and properties.
The cullet is melted in a large tank and formed into strip glass. The strip glass is slowly cooled using a continuous annealing Lehr to remove stress. The strip glass exits the annealing tunnel quite slowly.
Measurement: Important properties such as refractive indices and internal transmittance are measured via a sampling method.
Inspection of glass: After cutting the Strip glass, samples are inspected for bubbles, striae and inclusions via bright light and striaescope.
Another quality control is the investigation for stress birefringence. Tensions in the glass are localizable by the optical birefringence which they cause.
The final product is an optically high-purity and striae free glass bar.