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Warm water rinse superior?

  1. Aug 2, 2005 #1
    A friend of mine just got a new washing machine. In its manual it states "cold water rinses do not wring out the clothes as well as warm water rinses". She asked what the scientific basis for that is since she had never heard it before. I gave it a lot of thought but for the life of me I can't figure out why that statement would be true.

    Does anyone here know if this is true and if so, why?

    Thanks.

    :smile:
     
  2. jcsd
  3. Aug 2, 2005 #2

    Danger

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    First off, no amount of any kind of water will 'wring out' the clothes. That's a mechanical/manual process for removing water. As for rinsing out detergent, warm water dissolves other substances better than cold, and so would probably remove more of the soap with less water.
     
  4. Aug 2, 2005 #3

    Astronuc

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    Two things -

    Danger is correct - solubility of soaps and detergents increase with increasing temperature.

    As for the effect of wringing, the fibers/fabric are 'stiffer' in cold water so they will 'wring out' less effectively than in warm water.
     
  5. Aug 2, 2005 #4
    Having done laundry for too many years to mention, I have noticed that jeans seem to come out of the machine wetter/heavier when they are rinsed with cold water. I have no idea why.
    I would contact the maker of the washer{often a toll free number} and ask them why.


    added* Astro...geesh...I'm suffering from stiff jean syndrome?
     
    Last edited: Aug 2, 2005
  6. Aug 2, 2005 #5

    Gokul43201

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    I agree that one reason for the hot water rinse is the point was first raised by Danger. While soaps are not inorganic salts, they too have a positive temperature coefficient of solubility (because, among other reasons, they posses negligible vapor pressure). Judging from the solubilities of common inorganic salts one might guess that soaps are noticeably more soluble in warm water.

    As for the weight of the clothes, it would make sense that after a hot rinse, a good portion of the water evaporates out (leaving the clothes lighter than if you used a cold rinse). In addition to Astronuc's point, this may be a reason why hot rinses are said to "wring" out better.
     
    Last edited: Aug 2, 2005
  7. Aug 2, 2005 #6

    Bystander

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    Surface tension cold is higher than hot --- more mass retained between fibers. Viscosity cold is higher than hot --- probably an insignificant effect in reduction of flow rate through fbiers during a spin cycle, but worth considering.

    Fibers/polymers stiffer at low T? Wrong! Back to the thermo books, folks.
     
  8. Aug 2, 2005 #7

    brewnog

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    Warm water will activate any enzymes (biological catalysts) used in the detergent.
     
  9. Aug 3, 2005 #8
    Thanks for the ideas folks. You came up with more than I could.

    :smile:
     
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