# Heat at which shampoo will turn into something else

**URL:** <https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114>\
**Category:** Factual Questions\
**Created:** [February 14, 2016, 2:26pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114 "2016-02-14T14:26:03Z")\
**Posts on this page:** 6\
**Page:** 1

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**Author:** ![Velocity](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/velocity/32/18006_2.png) [@Velocity](https://boards.straightdope.com/u/Velocity)\
**Post date:** [February 14, 2016, 2:26pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/1 "2016-02-14T14:26:03Z")

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Let’s say you take Head & Shoulders shampoo - which is somewhat oily - and put it under the direct hot blast of a hair dryer inches away. Would it turn into a different chemical?

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**Author:** ![si\_blakely](https://avatars.discourse-cdn.com/v4/letter/s/d9b06d/32.png) [@si\_blakely](https://boards.straightdope.com/u/si_blakely)\
**Post date:** [February 15, 2016, 5:58pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/2 "2016-02-15T17:58:15Z")

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Probably not. But conditioners and oily shampoos are emulsified, and excessive heat will probably cause it to “split” into a soapy water fraction and an oily fraction.

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**Author:** ![Lightray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lightray/32/391_2.png) [@Lightray](https://boards.straightdope.com/u/Lightray)\
**Post date:** [February 16, 2016, 5:45pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/3 "2016-02-16T17:45:43Z")

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The decomposition temperature of a detergent is largely dependent on the chain length of the organic molecule. The abstract of [this study](https://www.google.com/#q=303K+%3D+celcius) suggests decomposition is occurring between 303K (~86F) and 443-463K. The lower end of that range seems more likely; even high-temperature detergents usually decompose well before 443K. So, it looks possible that a hairdryer could decompose shampoo.

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**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\
**Post date:** [February 16, 2016, 6:07pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/4 "2016-02-16T18:07:10Z")

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I think you put in the wrong link. Good info though.

For one point of comparison, in the I routinely use SDS (aka sodium dodecyl sulfate, SLS, sodium lauryl sulfate), one of the common detergents in shampoo and a lot of other household products. I can boil it over and over again without functional degradation. That’d make it immune to a hairdryer, but not a proper heat gun.

There are lots of other detergents and compounds in shampoo, some volatile, some which probably decompose or react at lower temperatures than SDS.

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<div class="post-metadata">

**Author:** ![Lightray](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/lightray/32/391_2.png) [@Lightray](https://boards.straightdope.com/u/Lightray)\
**Post date:** [February 16, 2016, 7:06pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/5 "2016-02-16T19:06:36Z")

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Whups. Should be this on [Thermal Decomposition of Shampoos](http://www.sciencedirect.com/science/article/pii/0040603187883235) (full study available for purchase).

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**Author:** ![lazybratsche](https://avatars.discourse-cdn.com/v4/letter/l/ba8739/32.png) [@lazybratsche](https://boards.straightdope.com/u/lazybratsche)\
**Post date:** [February 16, 2016, 7:52pm UTC](https://boards.straightdope.com/t/heat-at-which-shampoo-will-turn-into-something-else/746114/6 "2016-02-16T19:52:22Z")

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Thanks. It sounds like any decomposition starting at 303 K is merely evaporation of water and other assorted volatiles:

> [@](#):
>
> The thermal decomposition of 31 shampoos was investigated. The decomposition of these formulations has been found to proceed in three stages. In the temperature range from 303 K to 443–463 K, a mass loss of 72 to 93% occurred, which is connected with the release of liquid components of the shampoos. In the second and third stages, a mass loss of ca. 12% is observed, which is associated with the decomposition of the remaining components of the formulation. The residue after the decomposition of shampoos is a mixture of inorganic compounds.