# Cracking glass with hot/cold fluids?

**URL:** <https://boards.straightdope.com/t/cracking-glass-with-hot-cold-fluids/533170>\
**Category:** Factual Questions\
**Created:** [March 20, 2010, 9:03pm UTC](https://boards.straightdope.com/t/cracking-glass-with-hot-cold-fluids/533170 "2010-03-20T21:03:35Z")\
**Posts on this page:** 2\
**Page:** 2

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**Author:** ![Kimstu](https://avatars.discourse-cdn.com/v4/letter/k/ecd19e/32.png) [@Kimstu](https://boards.straightdope.com/u/Kimstu)\
**Post date:** [March 22, 2010, 5:22pm UTC](https://boards.straightdope.com/t/cracking-glass-with-hot-cold-fluids/533170/21 "2010-03-22T17:22:21Z")

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> [@constanze](#):
>
> You pour the very concentrated tea into the glass, and then add the hot water, both with a huge flourish by pouring from one foot above the glass…). Given si blakely’s explanation about Deltas, I wondered why those glasses didn’t crack more often simply from the hot tea.

I’d guess that for one thing, pouring liquid in a thin stream from high above the glass cools it down a little bit and fills the glass more slowly, giving it time to heat up.

I use this method when I have to add melted chocolate to beaten eggs in baking recipes and am too impatient to let the chocolate cool down but don’t want to curdle the eggs by dumping the hot melted chocolate on top of them. With one hand you hold the chocolate saucepan high above the mixing bowl and pour in a thin stream, while with the other you constantly stir the falling chocolate into the eggs. You end up with a smooth mixture that’s not overheated or curdled.

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**Author:** ![Yorikke](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/yorikke/32/4335_2.png) [@Yorikke](https://boards.straightdope.com/u/Yorikke)\
**Post date:** [March 22, 2010, 9:35pm UTC](https://boards.straightdope.com/t/cracking-glass-with-hot-cold-fluids/533170/22 "2010-03-22T21:35:02Z")

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For what it’s worth, I once took a coffee urn, very similar to one of [these](http://www.samsclub.com/shopping/navigate.do?dest=5&item=119335&pid=_Froogle&ci_src=14110944&ci_sku=624578), lined with glass, freshly and quickly emptied, and filled it with cold water to rinse it. It fricking EXPLODED in my face. luckily, the opening in the urn was too small for fragments to come out.

ETA : Perhaps “exploded” is too strong a term. The glass lining made a very loud popping sound, collapsed in on itself, and sprayed me with water. Use whatever term you’d like.

Joe

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