By definition, soap is fat or oil mixed with an alkali. The oil comes from an animal or plant, while the alkali is a chemical called lye. In bar soap-making, the lye is sodium hydroxide.

She dried her hands on her apron, and Mrs. Delacroix said, “You’re in time, though. They’re still talking away up there.” Mrs. Hutchinson craned her neck to see through the crowd and found ...