Thanks to Pennsylvania Salt Mfg. Co.,
Lewis Lye was introduced in the 1930's as a standard for sodium hydroxide. They later sold the company to Red Devil® (Reckitt & Coleman) which now solely advertises it as a drain cleaner. When the Lewis Lye Company sold out, the story goes that the new holding corporation didn't want the liability of offering a lye soap recipe on every can sold to the consumer for the purpose of opening clogged drains, and that they even managed to destroy every record of the old recipe.
Whether this is truth or legend, we aren't sure. There isn't a recipe for soap on the can anymore.
This is the recipe relayed by S. J. Fox from Palestine TX who wrote the recipe.
When mixing lye and water mixture, follow precautions in the directions. Render all clean fats. Clean rancid fats by boiling in equal volume of water. Remove from heat. Chill by adding one quart cold water for each gallon of liquid. Remove firm fat from top.
Use one can (Please note this WAS a 12 ounce lye can when this recipe was published. Container weight may vary. Always weigh lye before using from any container), 2 1/2 pints cold soft water, use 6 lbs. fat (tallow, lard, oil or combination), This makes 9 pounds hard soap. Slowly add lye to 2 1/2 pints cold water, stirring to dissolve. Melt 6 pounds fat and allow to cool to proper temperature.
If you use sweet lard or soft fat, warm to 85 degrees F,
with lye solution at 75 degrees F.
Combinations of lard, tallow and /or oil: 110 degrees F
with lye solution at 85 degrees F.
All tallow or all oil; 130 degrees F,
with lye solution at 95 degrees F.
Pour lye solution* into melted fat or oil in a thin slow steady stream with slow, even stirring. Rapid pouring or stirring causes separation. With oil, keep at 130 degrees F. Continue to stir until wooden spoon stands by itself. When all lye is incorporated into the fat and the spoon stands alone, pour into wooden or cardboard container lined with plastic wrap.
Leave 24 hours. Remove and cut into bars. Keep dry at room temperature for 2 weeks to cure.