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How Optical Glasses Are Manufactured
There are more than 70 kinds of raw materials used for manufacturing optical glass. Generally, 5 to 15 kinds of raw materials are used to manufacture one type of glass. All raw materials used for optical glass require very high purity.
Blended ingredients undergo vitrification while melting in a quartz crucible. Then, the vitrified ingredients melted in a platinum crucible at 1250 - 1400°C.
The melted glass is annealed and turned into various shapes, such as blocks, bars, and plates. Glass parts containing bubbles and striae are removed from the glasses. Each glass block is checked by visual inspection. A high level of skill is required for the inspection to detect uniformity in glass.
Inspected glass are cut into various shapes, or after reheated until soft, pressed into shape with molds. Pressed blanks are economical, and suitable for high-mix low-volume production.