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Name: Emmanuel
Status: student
Grade: 9-12
Country: Romania
Date: Spring 2013

Could you please explain the making bologna glass? I know that it involves cooling down rapidly one side of the glass whilst the other side is cooled down slowly, if I am correct. Could you help me understand how this was done without breaking the glass?


This is the only reference I could find in regard to ?Bologna Glass.? Go to and try your luck.

Sincere regards, Mike Stewart

Hi Emmanuel,

Thanks for the question. I am unfamiliar with Bologna glass. When glass is cooled rapidly, the glass does not have enough time for all the internal stresses to be relieved. This rapid cooling results in what we call "un-annealed glass" and this type of glass is quite brittle. I would be careful with un-annealed glass as it can shatter spontaneously. (I have experienced this several times myself.)

I suspect that the side that cools down slowly releases some heat which causes the rapidly cooled side to partially anneal and thus relieve some of the internal stresses in the glass. This partial annealing may make the glass a little more resistant to shattering.

I hope this helps. Please let me know if you have more questions. Thanks Jeff Grell

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