Re: silky or slimy?
Posted by chemical engineer on February 03, 2004 at 10:33:15:
In response to Re: silky or slimy?

Soaps are surface active agents (surfactants) which means they have one end that is ionic (hydrophillic)and another end that is more oil-like (hydrophobic.
Hard water does not lather as well as soft water because much of the soap is precipitated in solution by the hard water ions (Ca, Mg).
That means soft water has more active soap on the surface, where it can gather dirt and remove it. The soap loading is reduced when it is stuck to dirt (less bubbles as soap is used).
Your skin has oils in it that like the hydrophobic end of the soap molecule.
Rinse water that is hard removes soap from skin in the same way dirt removes active soap from the water surface.
Therefore, soft water is less able to remove soap from surfaces, like your skin, even though the soft water will remove dirt better (more active soap molecules).
That is why your skin feels slippery when you use soft water - soap is stuck there and the hydrophillic ends repel each other slip)due to common ionic charge.
All water softener companies will tell you the slippery feeling is your natural skin oils, but they want you to buy their product.

Bottom line - soft water cleans better for a given amount of soap, but hard water rinses soap off surfaces more easily.
Hard water will clean just as well as soft water, but you need more soap to do it.

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