Must soap lather to have a cleaning effect?

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Must soap lather to have a cleaning effect?
« on: 03/08/2008 10:18:46 »
simon_p_arnold asked the Naked Scientists:

While in the shower I got to wondering (as you do) is it necessary for soap to produce a lather for it to actually work?

If not, why do I  spend so much time and energy trying to produce it when I shampoo or shower?
Simon (from Cottenham)

What do you think?


Offline chris

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Must soap lather to have a cleaning effect?
« Reply #1 on: 03/08/2008 12:05:28 »
I don't believe so; however since our expectation is that soap must produce foam then manufacturers try to make sure that it does to avoid disappointment.

Detergents can make bubbles because they reduce the surface tension of water, reducing the collapsing force so a bubble is easier to create and sustain. This process is, however, independent of the cleansing chemistry of the soap.

As evidence of this, automatic washing machine powders contain foam suppressants to prevent the machine filling with suds, and cleaners like "Flash", which are nevertheless powerful detergents, form virtually no bubbles at all.

This is because soap cleans by forming interactions with the oily muck on the skin; because the soap molecules contain water-loving and oil-loving regions the soap can pluck the grease off your skin and then make it dissolve by using the water-loving part of the molecule.

« Last Edit: 07/08/2008 22:07:10 by chris »
I never forget a face, but in your case I'll make an exception - Groucho Marx