69｜Glass Manufacturing Methods, Forming Methods, Processing Methods 7

Hello everyone! 🎵

We've discussed the characteristics of different glass materials, including soda-lime glass, crystal glass, and borosilicate glass. Now, we'll delve into the manufacturing process.

Glass manufacturing, which began in the Middle Ages, has remained fundamentally the same, even as it transitioned from handcrafted production to automated machinery. The equipment hasn't changed significantly either, apart from the heat source for melting glass, which evolved from coal to oil, electricity, and so on.

Whether it's an industry lacking innovation or one whose initial technical potential was so high that further transformation or innovation hasn't been necessary, the perspective varies. In a way, excellent manufacturing techniques have been continuously passed down through generations.

The manufacturing methods for glass and glass bottles follow the same process, despite differences in equipment scale. This explains why Isomura Glass, a glass bottle manufacturer (with a large market share), produces tableware under the Adelia Glass brand, and Toyo Sasaki Glass, a subsidiary of Toyo Glass, manufactures and sells glasses – it's all due to the shared manufacturing process.

The manufacturing process involves six steps: ① Raw material blending, ② Melting, ③ Forming, ④ Annealing, ⑤ Finishing and inspection, and ⑥ Packaging and shipping.

For raw material blending, silica sand, soda ash, and lime, as explained for soda-lime glass materials, are finely crushed to make them easier to melt and then mixed uniformly. This mixture is called a batch.

Silica sand, being essentially sand, can be found anywhere on Earth. However, for glass manufacturing, it must have low impurities (impurities prevent transparency) and fine grains (generally less than 0.5mm for general glass) to melt easily. Such silica sand is found in Australia and Southeast Asia. Fratelli silica sand is abundant in the coastal areas of northeastern Australia's tropical regions. Sarawak silica sand is mined in northern Borneo and imported through major trading companies.

Soda ash, a chemical industrial product, is almost entirely domestically produced in Japan, and lime is also supplied domestically. The composition ratio of base raw materials varies slightly among manufacturers and glass factories, often considered a trade secret for each factory. It also subtly changes depending on the items and products being manufactured, as well as the forming method and production volume. This is why the perception of transparency can differ among manufacturers and factories when you look closely at glass.