• Question: why do some wet things dry quicker than others? e.g tip ex and hair)

    Asked by lexie2610 to Chris, Josh, Rebecca, Rob, Susan on 17 Jun 2015.
    • Photo: Susan Cartwright

      Susan Cartwright answered on 17 Jun 2015:

      Two reasons.
      One is that some “wet” things are not wet because they contain water, but because they contain some other fluid, usually alcohol. Alcohol has a lower boiling point than water, and so evaporates much more quickly. This applies to some kinds of varnish, for example, and quite likely Tipp-Ex (I haven’t checked the ingredients of Tipp-Ex).
      The other reason is that water evaporates from the surface, but is held in the volume. Thus anything that is spread out into a thin flat surface or a lot of fine strands will dry more quickly. This is why you spread clothes out to dry instead of bunching them up. Your hair (if long) will also dry quicker if you fan it out than if you gather it up into a bun.

    • Photo: Rebecca Dewey

      Rebecca Dewey answered on 18 Jun 2015:

      Also, a liquid that is nearer its boiling point will evaporate faster than one that is quite a lot colder than its boiling point. So if you rinse your hair in hot water it will dry quicker than if you rinse it in cold water – up until the point that all the hot water molecules have evaporated, leaving just the cold ones behind!

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