Why does a bar of soap produce a great lather when it’s new, then not at all when it’s smaller?

Question

It’s supposedly the same soap through and through, all the way to the core of the bar, right? Why does it react so differently to water and being rubbed on skin when it is reduced to a sliver?

In: 718

Answer 1

If you have hard water, the magnesium and calcium ions in your water will bind to your soap turning it from soap into insoluble soap scum. The older the bar of soap, the more of it that can convert into soap scum.