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2steps
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oldish chris
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jamanda Downsizer Moderator
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quixoticgeek
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Luath
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quixoticgeek
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2steps
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2steps
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VM
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Dee J
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chickenann
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jamanda Downsizer Moderator
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oldish chris
Joined: 14 Jun 2006 Posts: 4148 Location: Comfortably Wet Southport
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Posted: Sun Nov 03, 13 9:34 am Post subject: |
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quixoticgeek wrote: |
Normal glass jars are fine with heat, and with cold, they just don't like changes in heat. If you take a hot jar and cool it rapidly, it won't like it. But as long as you don't take it out the oven and put it straight on a cold metal surface you'll be fine.
J |
In my experience, which includes working in a jam factory, what quixoticgeek says is totally correct. Those of you who have come across really old kilner jars will notice that the thickness of the glass can be somewhat variable, and that is what makes gradual heating and cooling so important, which also explains why classic (i.e. re-war) books on preserving go on at great lengths about it. As for modern jam-jars, just imagine what its like in a factory, with thousands of jars whizzing along conveyor belts! The jars are designed to take quite considerable heat shocks. In 40 years of lackadaisical home preserving I've never had a problem. |
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Luath
Joined: 03 Dec 2009 Posts: 761
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