Guest random Posted May 22, 2005 Share Posted May 22, 2005 Does anyone know how hot some glass, say a jam jar for example can get before it cracks? Link to comment Share on other sites More sharing options...
budullewraagh Posted May 22, 2005 Share Posted May 22, 2005 glass varies in purity and composition. could you please specify? Link to comment Share on other sites More sharing options...
Ophiolite Posted May 22, 2005 Share Posted May 22, 2005 Geometry (shape and thickness), as well as where and how heat is applied will have an influence. Link to comment Share on other sites More sharing options...
akcapr Posted May 22, 2005 Share Posted May 22, 2005 it depends on how fast the glass crystals expand. If u have a more rounded jar it will have less tendency to crack, but if the jar has a flat bottom, the crystals will morph/expand at different rates causing the glass to crack. ALso, evenly heating glass can help prevent cracking. Link to comment Share on other sites More sharing options...
jdurg Posted May 22, 2005 Share Posted May 22, 2005 Generally speaking, however, glass has no crystal structure. It is an amorphous solid and has no set melting point. Instead, it just softens and then melts. Now crystal glassware, however, does have a crystal structure and that will melt at a certain point and crack at a certain point. You're more in danger of glass cracking if you take it from a hot environment into a cold environment. Link to comment Share on other sites More sharing options...
raivo Posted May 22, 2005 Share Posted May 22, 2005 Does anyone know how hot some glass, say a jam jar for example can get before it cracks? If you heat it slowly with hot air so that temperature difference will never exceed 50C in any part of jam jar then it does not crack, just starts to soften at 400C or maybe 500C. Common glass cracks if temperature difference between nearby points is at least 80C ... 120C. Temperature in itself does not count, just difference. Link to comment Share on other sites More sharing options...
Guest random Posted May 23, 2005 Share Posted May 23, 2005 Thanks for the replies, I've found out what I needed to now Link to comment Share on other sites More sharing options...
Mendelejev Posted May 23, 2005 Share Posted May 23, 2005 99,7 % SiO2 Density 2,2 Melting point 2300 °C (Go not above 1300 °C) Same properties as Duran, Pyrex and Simax Duran Pyrec Simax Density 2,23 Melting point 530 °C (Go not above 500 °C) Composition : 81 % Boron oxide, 4 % sodium-potassium, 2 % aluminium oxide SBW Density 2,45 Melting point 555 °C (Go not above 500 °C) Ceran Density 2,57 Melting point 700 °C (Go not above 700 °C) Sodaglass, AR, Soda-potassium Density +/_ 2,5 Melting point 300 °C (Go not above 300 °C) Composition : 74 % silicium, 16 % soda, 9 % calcium carbonate and magnesium Link to comment Share on other sites More sharing options...
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