GLASS
Raw Materials:
- Silica Sand: The primary component of glass is silica, obtained from high-quality silica sand.
- Soda Ash: It is added to lower the melting point of silica and improve its workability.
- Limestone: Used to stabilize the chemical composition of the glass.
- Other additives: Depending on the desired properties, various additives like alumina, borax, and colorants can be incorporated.
Transparent Glass: Silica Sand: Approximately 70-75% Soda Ash: Typically around 12-18% Limestone: Usually 5-12% Other additives: Varying amounts, depending on the specific requirements (typically less than 5%)
Optical Lens Glass: Silica Sand: Typically around 60-70% Soda Ash: Often in the range of 10-15% Limestone: Generally around 5-10% Other additives: These can vary significantly depending on the specific lens requirements (usually less than 5%)
Additives:
Alumina (Aluminum Oxide): It improves the chemical resistance and durability of the glass.
Borax (Sodium Borate): Borax can enhance the thermal and chemical resistance of the glass. It also aids in reducing the melting temperature and improving workability.
Calcium Oxide: It influences the glass's optical properties and stability.
Magnesium Oxide: This additive can increase the durability and impact resistance of the glass.
Potassium Oxide: It can modify the glass's refractive index and electrical properties.
Lead Oxide: Adding lead oxide to the glass composition can increase its refractive index, making it suitable for applications like optical lenses and fine crystal.
Titanium Dioxide: It is used to provide opacity or whiteness to certain types of glass.
Colorants: Various metal oxides such as cobalt, manganese, iron, selenium, or neodymium can be incorporated to give the glass specific colors and shades.
Procedures:
- Batch mixing: The raw materials, including silica sand, soda ash, limestone, and other additives, are mixed together in the desired proportions. This mixture is called "batch."
- Melting: The batch is then heated in a furnace at extremely high temperatures, usually above 1500°C (2730°F). The intense heat causes the raw materials to fuse together and form a molten liquid called "glass melt."
- Refining: The glass melt undergoes further heating and refining to eliminate any impurities or bubbles. This process ensures the glass achieves the desired clarity and consistency.
- Shaping: The molten glass can now be shaped into various forms using different techniques such as blowing, casting, pressing, or drawing. The chosen method depends on the desired final product.
- Annealing: After shaping, the glass is slowly cooled to reduce internal stresses and increase its strength. This is typically done through a carefully controlled cooling process called annealing.
- Finishing: Once the glass is cooled, it undergoes additional processes such as cutting, grinding, polishing, and sometimes coating to achieve the desired aesthetic and functional properties.
Page Source