Lye is a powerful chemical substance used for cleaning and making soap. For thousands of years, people made lye by pouring water through wood ashes, which produced a slippery, caustic liquid that could break down grease and fat.

Lye is extremely dangerous if it touches your skin or eyes because it causes severe burns. That's why soap makers today wear protective gloves and goggles when working with it. Despite being hazardous in its pure form, lye transforms during the soap-making process. When lye mixes with oils or fats in just the right proportions, a chemical reaction called saponification occurs, turning both ingredients into safe, gentle soap. None of the original lye remains in the finished bar.

Before modern cleaning products existed, lye was essential for pioneer families. They used it for making soap, cleaning floors, washing clothes, and even preparing certain foods like hominy and lutefisk (though you'd need to know exactly what you were doing). Today, commercial soap makers still use lye, and some traditional bakers use it to give pretzels their distinctive brown, shiny crust.