This article needs additional citations for verification. Please help improve this article by adding reliable references. Unsourced material may be challenged and removed. (December 2007)

Reusable soda-lime glass milk bottles

Old window made from soda-lime flat glass, Jena, Germany. Interesting are the distorted reflections of a tree that give an indication that the flat glass was possibly not made by the float glass process.

Soda-lime glass, also called soda-lime-silica glass, is the most prevalent type of glass, used for windowpanes, and glass containers (bottles and jars) for beverages, food, and some commodity items. Glass bakeware is often made of tempered soda-lime glass.^[1]

Soda-lime glass is prepared by melting the raw materials, such as sodium carbonate (soda), limestone, dolomite, silicon dioxide (silica), aluminium oxide (alumina), and small quantities of fining agents (e.g., sodium sulfate, sodium chloride) in a glass furnace at temperatures locally up to 1675°C.^[2] The temperature is only limited by the quality of the furnace superstructure material and by the glass composition. Green and brown bottles are obtained from raw materials containing iron oxide. Relatively inexpensive minerals such as trona, sand, and feldspar are used instead of pure chemicals. The mix of raw materials is termed batch.

Soda-lime glass is divided technically into glass used for windows, called float glass or flat glass, and glass for containers, called container glass. Both types differ in the application, production method (float process for windows, blowing and pressing for containers), and chemical composition (see table below). Float glass has a higher magnesium oxide and sodium oxide content as compared to container glass, and a lower silica, calcium oxide, and aluminium oxide content.^[3] From this follows a slightly higher quality of container glass concerning the chemical durability against water (see table), which is required especially for storage of beverages and food.

[edit] Typical compositions and properties

The following table lists some physical properties soda-lime glasses. Unless otherwise stated, the glass compositions and many experimentally determined properties are taken from one large study.^[3] Those values marked in italic font have been interpolated from similar glass compositions (see calculation of glass properties) due to the lack of experimental data.

Typical transmission spectrum^{[citation needed]}

• Coefficient of restitution (glass sphere vs. glass wall): 0.97 ± 0.01^[6]
• Thermal conductivity: 0.9-1.3 W/m.K^[7]
• Hardness (Mohs scale): 6–7^{[citation needed]}
• Knoop hardness: 585 kg/mm² + 20^{[citation needed]}

[edit] See also

• Glass batch calculation

[edit] References