[blam]

"Yes, you're absolutely right. Another source of potassium -- potash -- was wood ashes."

Mom said that when she was young they made their own soap using this ingredient/method. (she's 85)

[IronJack]

As I understand it, running water through wood ashes also produces sodium hydroxide, which is commonly known as lye. Lye is a saponification agent, which means it suspends fats and oils, like the oils on your skin. That allows water to more effectively dissolve contaminants on the skin, even though it does strip away much of the skin's natural protection.

Many alkalis -- and sodium hydroxide is one of the classics -- feel slippery to the touch. Thus the slick, "woops" feeling that soap has.

In the old days, the lye came from the ashes, and it was mixed with tallow -- beef or pig fat -- to make the soap. Today's soaps are similar, even if the process is somewhat more refined.

Ain't chemistry grand?