floydbloke:
OK here goes mine. Any personal hygiene material gurus here?
When you start with a fresh bar of soap it doesn't take a lot of rubbing to generate the lather.
As it gets used up more rubbing is required to produce the same amount of lather.
The surface area reduces so there is one obvious reason, but is it also a case that the 'potency' of the soap itself gets less?
I think there are two things at play.
1) The reduction of surface area which is dramatic.
2) The soap absorbs moisture