[whitecrow]

Originally Posted by WiNaDeYo

Gra’ma warned, though…
“..if you got too much lye in it (the soap), it’d eat your fingernails off. If you washed and put your hands in that soap, it’d just make your fingernails curl up. And so you had to be careful about that.”

Therein lies the disadvantage of making lye the old-fashioned way. It's more art than science. The old way of knowing when your lye solution was strong enough was to float an egg in it. And this process creates potassium hydroxide, which does not make hard soap. For that you need sodium hydroxide.

In the old days, lye-makers were called ashers because of the process used. The wooden rigs used to percolate the ashes were called ashies. When the lye water was heat-dried to a powder it was called potash. And when kiln-dried into granules it was called pearlash. All that came to an end when the process for making sodium hydroxide from brine was invented. It was this invention that allowed soapmaking to make the leap from a cottage industry to a true industrial process.

Old-fashioned lye soap was often harsh because there was no way to measure the strength of the lye accurately, hence no way to know for sure what percentage of the fats and oils were saponified. Frequently they were completely saponified with lye left over, which is what made the stuff burn.

Today we can make soap with a controlled lye discount - which would have been impossible with home-made lye. On the other hand, in a survival situation it would be good to know how to make this most useful chemical.