bilglass
11 12 3 12 13 3 Glass Transition Temperature, Tg 12 13 Annealing Point Stress is relieved within a several minutes 13 5 14 5 Strain Point Stress is relieved within several hours edit Glass production history Glass melting technology has passed through several stages: 7 Glass was manufactured in open pits, ca 3000 B C until the invention of the blowpipe in ca 250 B C The mobile wood fired melting pot furnace was used until around the 17th century by traveling glass manufacturers Around 1688, a process for casting glass was developed, which led to glass becoming a much more commonly used material citation needed The local pot furnace, fired by wood and coal was used between 1600 and 1850 The cylinder method of creating flat glass was used in the United States of America for the first time in the 1820s It was used to commercially produce windows citation needed The invention of the glass pressing machine in 1827 allowed the mass production of inexpensive glass products citation needed The gas heated melting pot and tank furnaces dating bilglass interi-rglass sikkerhetsglass from 1860, followed by the electric furnace of 1910 Hand blown sheet glass was replaced in the 20th century by rolled plate glass citation needed The float glass process was invented in the 1950s edit Glass ingredients Quartz sand silica as main raw material for commercial glass production Pure silica SiO2 has a “glass melting point” at a viscosity ? 100 Poise of over 2,300°C 4,172°F While pure silica can be made into glass for special applications see fused quartz , other substances are added to common glass to simplify processing One is sodium carbonate Na2CO3 , which lowers the melting point to about 1,500°C 2,732°F in soda lime glass “soda” refers to the original source of sodium carbonate in the soda ash obtained from certain plants However, the soda makes the glass water soluble, which is usually undesirable, so lime calcium oxide CaO , generally obtained from limestone , some magnesium oxide MgO and aluminum oxide are added to provide for a better chemical durability The resulting glass contains about 70 to 74 percent silica by weight and is called a soda lime glass 7 Soda lime bilglass interi-rglass sikkerhetsglass