Glass Manufacture

In-depth explanation of Glass Manufacture

Glass is an amorphous solid usually made from silica sand, soda ash and limestone. These raw materials are melted at about 1500 C, where soda ash lowers the melting temperature and limestone improves chemical durability. The molten glass is shaped by floating, pressing, blowing or drawing, and then annealed by slow controlled cooling to relieve internal stress. Float glass is produced by pouring molten glass onto a bath of liquid tin, which gives a flat and smooth surface. Recycled glass, or cullet, reduces the energy required for melting.

Going deeper: Glass Manufacture

Key ideas: Soda-lime glass: about 70 percent silica sand SiO2, 15 percent Na2O (from soda ash Na2CO3), 10 percent CaO (limestone), melted near 1500 C. Borosilicate (Pyrex) has B2O3 for low thermal expansion, lead glass has high refractive index, colors from metal oxides (Co blue, Cr or Fe green, Cu or Se red). Annealing relieves stress.

Common mistakes and connections: Mistake: classifying glass as crystalline solid; it is an amorphous supercooled-like solid with no sharp melting point and no long-range order. Soda lowers melting temperature but makes it water soluble, so lime is added. Links to silicates, giant structures and cement.

Visualization of Glass Manufacture

Soda ash and limestone let glass melt near 1500 C instead of the 1713 C of pure silica, followed by controlled cooling to relieve stress. The interactive lesson shows this as a live animation or chart.

Worked example and use case

Adding cullet to the furnace lowers the melting energy needed for each batch.

Where Glass Manufacture fits in Biochemistry, Environment & Industry

Glass Manufacture is topic 104 of 127 in Biochemistry, Environment & Industry.

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