When I was a little girl, my grandmother made old fashioned lye soap with me during my summer visits. I still remember the unmistakable clean smell of that soap.
Back in the old days, lye soap was used for all of a family's cleaning needs, from bathing and laundry to scrubbing stuff around the house. Materials were easily obtained, just leftover scraps of fat, and the lye obtained from slowly pouring water through wood ashes left from fires.
Here is a recipe like the one my grandmother used:
13 ounces of lye
2 1/2 pints of cold water
6 pounds of lard
Dissolve the lye in the water and allow it to cool (cold water becomes hot when lye is added). Melt the fat in a steel saucepan, then let it cool until it becomes thick. Add the lye/water mixture by drizzling it into the thickening fat, stirring constantly until it reaches the "trace" stage, which means that when fat is drizzled across the surface of the soap it stays raised and doesn't sink in immediately.
Pour the soap into molds or make your own using a cardboard box lined with a plastic trash bag liner.
Allow it to rest for three hours before dividing it into separate, bar-size pieces. Wait three weeks so that the soap can cure and become mild enough for use. (And enjoy the clean smell!)