glassmaking

Glassmaking is the production of glass, a non-crystalline, transparent solid, by fusing silica-based materials with additives. The common raw batch consists of silica sand, soda ash as a flux, and limestone to improve durability, with small amounts of other oxides to adjust color, durability, and melting behavior. Recycled glass, or cullet, is frequently added to lower melting temperatures and conserve energy.

Most glass is produced by melting the batch in a furnace at high temperatures, typically around 1400 to 1600°C. The molten glass is then formed into desired shapes or products through various processes. Traditional methods include glassblowing, where a gather of molten glass is inflated into a bubble; pressing and casting, where the material is shaped in molds; and drawing or forming for fibers and specialized shapes. For flat, continuous glass products, the float glass process, developed in the mid-20th century, allows molten glass to be floated on molten tin, producing highly uniform sheets used in windows and facades.

Common glass types include soda-lime glass, which dominates most packaging and window applications; borosilicate glass, notable for low thermal expansion and chemical resistance; and lead glass, which has higher refractive indices and is used in decorative items and optics. Other variants include tempered, laminated, and specialty glasses for optics, electronics, or high-temperature uses.

Industry considerations include energy intensity and emissions from furnaces, as well as recycling and cullet utilization. Glassmaking supports a wide range of applications, from containers and architectural glazing to laboratory glassware, fiber optics, and consumer electronics, reflecting its combination of transparency, chemical stability, and versatility.