# Wait, why did this catch fire?

**URL:** <https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484>\
**Category:** Miscellaneous and Personal Stuff I Must Share\
**Created:** [January 1, 2023, 8:54pm UTC](https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484 "2023-01-01T20:54:37Z")\
**Posts on this page:** 4\
**Page:** 1

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**Author:** ![Lumpy](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lumpy/32/446_2.png) [@Lumpy](https://boards.straightdope.com/u/Lumpy)\
**Post date:** [January 1, 2023, 8:54pm UTC](https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484/1 "2023-01-01T20:54:37Z")

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Someone heats wax in a test tube until it’s boiling. The test tube is then immersed in _cold_ water and the paraffin autoignites? WTH?  
[Paraffin Wax Autoignition - YouTube](https://www.youtube.com/watch?v=90iUn6lJdbE)

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**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\
**Post date:** [January 1, 2023, 9:14pm UTC](https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484/2 "2023-01-01T21:14:24Z")

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My best guess is that the paraffin vapor was hot enough, but it wasn’t well-enough mixed with the air. Putting it in cold water created sudden turbulence, which mixed the vapor and the air, which then led to the ignition.

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**Author:** ![penultima\_thule](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/penultima_thule/32/3833_2.png) [@penultima\_thule](https://boards.straightdope.com/u/penultima_thule)\
**Post date:** [January 1, 2023, 9:59pm UTC](https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484/3 "2023-01-01T21:59:58Z")

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Was thinking that the immersion in cold water caused the condensation of one/some paraffin fractions which were inhibiting the ignition of the paraffin vapour.

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**Author:** ![Crafter\_Man](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/crafter_man/32/458_2.png) [@Crafter\_Man](https://boards.straightdope.com/u/Crafter_Man)\
**Post date:** [January 2, 2023, 12:58am UTC](https://boards.straightdope.com/t/wait-why-did-this-catch-fire/977484/4 "2023-01-02T00:58:11Z")

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That was my WAG too: the “correct” [stoichiometric ratio](https://en.wikipedia.org/wiki/Stoichiometry) was achieved.