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At what temp. does crushed or recycled glass melt?

Last Updated: Dec 07, 2012  |  284 Views
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Soda lime glass melts at approximately 2370° 

From the British Glass Industry website (About Glass): 

"Most of the glass we see around us in our everyday lives in the form of bottles and jars, flat glass for windows or for drinking glasses is known as commercial glass or soda-lime glass, as soda ash is used in its manufacture. 
The main constituent of practically all commercial glass is sand. Sand by itself can be fused to produce glass but the temperature at which this can be achieved is about 1700oC. Adding other minerals and chemicals to sand can considerably reduce the melting temperature. 

The addition of sodium carbonate (Na2CO3), known as soda ash, to produce a mixture of 75% silica (SiO2) and 25% of sodium oxide (Na2O), will reduce the temperature of fusion to about 800oC. However, a glass of this composition is water-soluble and is known as water glass. In order to give the glass stability, other chemicals like calcium oxide (CaO) and magnesium oxide (MgO) are needed. These are obtained by adding limestone which results in a pure inert glass." 

Take a look at the British Glass website to learn more about other types of glasses and some of their melting temperatures. 

From the Corning Museum of Glass website :

Formers are the basic ingredients. Any chemical compound that can be melted and cooled into a glass is a FORMER. (With enough heat, 100% of the earth's crust could be made into glass.) 
Fluxes help FORMERS to melt at lower, more practical to achieve temperatures. 
Stabilizers combine with FORMERS and FLUXES to keep the finished glass from dissolving, crumbling, or falling apart. 
Chemical composition determines what a glass can do. There are already tens of thousands of workable glass compositions and new ones are being developed every day. 

Most commercial glass is made with sand that contains the most common FORMER, Silica. Other FORMERS include: 

Anhydrous Boric Acid 
Anhydrous Phosphoric Acid But melting sand by itself is too expensive because of the high temperatures required (about 1850°C, or 3360°F). THEREFORE... 
are added which let the FORMER melt more readily and at lower temperatures (1300°C, or 2370°). These include: 

Soda Ash 
Lithium Carbonate 
But FLUXES also make the glass chemically unstable, liable to dissolve in water or form unwanted crystals. THEREFORE... 

are added to make the glass uniform and keep its special structure intact. These include: 

Barium Carbonate 
Strontium Carbonate 
Zinc Oxide 

These books provide basic information about glass: 

Adams, P. Bruce [and others]. All About Glass. Corning, NY: Corning Glass Works, 1984. It covers types of glass, the structure of glass and manufacturing processes. 

Bray, Charles. Ceramic and Glass: A Basic Technology. Sheffield, UK: Society of Glass Technology, 2000. (written for students, potters and glassmakers working in small studios -- people with little or no scientific background) "Structure and basic chemistry," pp. 80-116. -- great source!) 

Pfaender, Heinz G. Schott Guide to Glass. 2nd ed. London and New York: Chapman & Hall, 1996. "General characteristics of the glassy state" pp. 16-22. 

Paterson, Alan J. How Glass is Made. New York: Facts on File Publications, 1985. 0-8160-0038-7 It simply explains (in a few pages) hand-made glass with photographs and drawn illustrations. It also provides an explanation of what glass is, notes different types of glass that can be made, describes furnaces, etc. 

These are more advanced books: 

Shelby, James E. Introduction to Glass Science and Technology. Cambridge, England: The Royal Society of Chemistry, 1997. xiii, 244 pp. (intro. college text) 

Vogel, W. Chemistry of Glass. Columbus, OH: The American Ceramic Society, 1985. (advanced text) 

If you wish to obtain copies of any of these items, please contact your local library. The Rakow Research Library is a member of the Online Computer Library Center (OCLC); your library can contact us through OCLC or they may mail an Interlibrary Loan form to us. You may request up to five items at a time. We send photocopies of articles and microfiche copies of our books (if they have been microfilmed) through Interlibrary Loan for four weeks use. 

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