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Glass production is an ancient process dating back to the Egyptian Pharaohs. Glass is one of the most versatile materials manufacturers use. Glass manufacturers can configure glass to have different physical, chemical, and optical properties.

How Glass is Made

Glass production begins by changing the chemical structure of the ingredients. Manufacturers heat the ingredients to 1700o C. To make liquid glass, one mixes sand, limestone, and soda ash, then heats them in giant furnaces. The blend of ingredients melts into a liquid. The ratio of the mixture determines the properties the final product will have.

Batching

Batching is mixing and weighing primary materials, which include silica sand, limestone (calcium carbonate), and soda ash (sodium carbonate). They are weighed and measured to exact proportions. The purity of the raw materials and precise mixing procedures help ensure the quality of the glass. The silica sand is purified, and excess iron is removed.

Refining

Modern glass is made from refined ingredients that have a more homogenous composition. Although soda lime glass is the most common, different substances and materials like magnesium oxide, calcium oxide, and aluminum oxide are used in modern glass production. Some glass varieties, such as borosilicate glass, don’t have soda content, while others lack silica, like phosphate glass.

Heating

The mixture is heated at 1700oC or 3000oF in a heating furnace and then rapidly cooled. The process of extreme heat and rapid cooling causes the mixture to lose its crystalline form. The mixture enters a condition called ‘amorphous solid’ - a molecular state between liquid and solid.

Tin Bath

The molten glass floats over a molten tin bath, forming ribbons. The 1700o C temperature decreases as it passes over the vat of molten tin. Tin bath glass production creates sheets of glass with even thickness and flat surfaces. Tin has a lower melting point than glass, so the molten glass solidifies and cools on top of the tin. Manufacturers can increase or decrease the molten glass flow to control the glass thickness.

Coating

When the cooled glass leaves the float, a hard or soft coating is applied to its surface at high temperatures. LoE coating is the application of a thin, colorless metallic coating that allows light through but blocks heat energy.

Annealing

In glass manufacturing, a special type of furnace called a lehr is used for annealing glass sheets. A lehr is a long oven that has several heating zones. The glass sheets move through the zones on a conveyor belt. Each form of glass requires a different annealing process to accommodate the glass composition, coefficient of thermal expansion, and thickness. The cooling process in the annealing oven can remove residual stress in the glass.

Three Types of Glass Construction

There are three basic glass constructions of sheet glass. Types are differentiated by layers of glass and materials placed between them.

Monolithic Glass

Monolithic glass is the simplest form of glass, consisting of a single piece of glass with one thickness.

Laminated Glass

Laminated glass consists of two panes of glass fused together with a middle layer of polyvinyl butylene film (PVB). PVB serves to bind the glass panes together

Insulated Glass

Insulated glass also has two panes of glass. Unlike laminated glass, insulated glass fills the space between panes with air. The air space minimizes heat transfer by conduction or convection.

Common Glass Compositions

Glass is engineered to have different properties by altering the materials used to produce it. Manufacturers use different compositions to fit structural and commercial requirements. Three common types of glass are borosilicate, soda lime silicate, and phosphates.

Soda Lime Silica Glass (CaHNaO2)

Soda lime silica glass is used to make containers and glass products found around the home, such as bottles, food containers, decorative tableware, and windows. It is popular among manufacturers because it is affordable to make. It’s easy to source materials, and the ingredients will melt at a lower temperature. The production of soda lime glass has been improved, perfected, and automated so much over centuries that it is mass-produced.

Soda lime silica glass is the least durable because it is susceptible to thermal shock and corrosive conditions. Glass manufacturers have perfected methods to enhance soda lime silica glass through chemicals and thermal strengthening.

Borosilicate Glass (SiO2, B2O3)

Borosilicate glass is used for its exceptional durability. It can withstand thermal shock and thermal cycling. Borosilicate glass is durable because it has a low thermal expansion coefficient. Therefore borosilicate glass undergoes fewer internal stresses during heating and cooling processes.

Borosilicate glass is resistant to moisture and chemical attacks. It is an ideal choice for abrasive conditions. Manufacturers use borosilicate glass to produce laboratory glassware, sight glass for machinery, transformer bushings, explosion-proof lights, and aircraft lenses.

Phosphate Glass (P2O5)

Phosphate glass is primarily made from phosphorus pentoxide with the addition of various compounds. It has a high optical range transmission that is narrower than silica glasses. Phosphate glass has a low optical damage threshold and low thermal conductivity. It is resistant to hydrofluoric acid and absorbs heat when iron oxide is added.

Choosing the right glass for a project depends on several factors, including environment and performance requirements. Manufacturers should consider the glass's optical, thermal, chemical, and mechanical properties before choosing the most affordable option.

Choosing the Proper Glass Manufacturers Company

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