Audiolab said:
Hi Henk,
Do you know what role heat plays in the lather (if any)? I know I can get a good lather mixed cold but I also know my face prefers hot lather and somehow it seems to reduce friction. Perhaps this is affecting the skin more than the lather, but wondered if heating the lather is good, bad or makes no difference.
I know from experience that too much heat seems to destroy lather but does a low heat have any ill effects on lather?
I'm not sure, but I think that
a] warm lather is more comfortable
b] cold water dissolves less fatty acid salts and it is therefore more difficult to make a good lather with cold water -- solubility is what makes potassium salts superior latherers over sodium salts
c] too much heat will blow the lather apart. What's more, a hot lather (i.e. essentially a lather with hot air inside its bubbles) will collapse on cooling
So, my reasoning here is that there is an optimum lathering temperature based in part on soap solubility and comfort, and that no matter what temperature your lather is when you make it, you want to keep it roughly at that temperature for ultimate stability
Henk