Also known as NaOH, caustic soda and lye. This is an inorganic chemical at minimum 99% pure. It is a white solid and highly caustic metallic base and alkali salt. Sodium hydroxide is soluble in water, ethanol and methanol. This alkali is deliquescent and readily absorbs moisture and carbon dioxide in air. In Soap Making: Lye is mixed with water to create a lye solution. Lye solution, when mixed with fats and oils, will cause a chemical reaction called saponification (fancy for soap). The result of saponification is beautiful handmade soap. In Cleaning: Industrial, or technical, grade lye is often used as a cleaner and is the active ingredient in common drain cleaners.