Types of glass
There are many different types of glass. They differ in terms of their chemical composition, the method used to produce them or their processing behaviour. Generally, they are categorised according to their chemical composition. A differentiation is made between
soda-lime glass, lead glass and borosilicate glass. These three types of glass make up around 95 percent of the cullet glass used in the production process. The remaining 5 percent of glass is special-purpose glass.
Soda-lime glass is the glass produced in by far the largest quantities of all mass produced glass types. As the name indicates, the main constituents in addition to sand are soda and lime. A typical soda-lime glass contains 71 to 75 percent sand (SiO2), 12 to 16 percent sodium bicarbonate (Na2O), 10 to 15 percent lime (CaO) and small quantities of other substances such as dyes. Soda-lime glass is used to make bottles, food jars, simple drinking glasses and sheet glass products. Soda-lime glass is light permeable and has a smooth, fine-pored surface, making it easy to clean. It also expands very quickly under the influence of heat so care should always be taking when putting hot water into a soda-lime glass container.
Crystal glass looks beautiful when cut as a result of its high refraction index. It has a far higher density than soda-lime glass. In our everyday lives, we use crystal glass to make drinking glasses, vases, bowls, ashtrays and decorative ornaments. Its composition is 54 to 65 percent sand, 13 to 15 percent alkali oxide and several other oxides. Glass containing more than 18 percent lead oxide is also known as lead crystal glass. However, lead oxide is hardly used today in glass production. Crystal glass only accounts for less than 0.5 percent of total tableware glass production in Germany.
70 to 80 percent by weight of borosilicate glass is sand. Seven to 13 percent is boron trioxide, four to eight percent is sodium and potassium oxide and two to seven percent aluminium oxide. Glass with this composition is highly resistant to chemicals and temperature fluctuation. That's why it is mainly used for chemical production applications, in laboratories, for ampoules and bottles containing pharmaceuticals, to package injectables, or as extremely durable lamp covers. Borosilicate glass is also used in the household for baking and soufflé dishes and other "heatproof" kitchenware.
Special glass is used for special technical and scientific applications. Its composition can vary and it includes numerous chemical elements. Examples of special glass are lenses, glass products used by the electrical and electronics industries and glass ceramics.
Glass is a solid produced from a molten substance. From a physical viewpoint, glass is an undercooled liquid. At room temperature glass is solid, at approximately 1,000°C it is formable and at temperatures of between 1,400°C and 1,650°C it melts. Glass has many positive and practical properties which make it an indispensable packaging for foods, beverages or cosmetics, innovative glass fibre optic cables for data transmission and practical glass ceramic cooktops.
Here’s an overview of properties. Glass…