Sodium hydroxide (lye) at room temperature, is a white crystalline odorless solid that absorbs moisture from the air. When dissolved in water or neutralized with acid it liberates substantial heat. Sodium hydroxide is very corrosive. It is generally used as a solid or a 50% solution. Other common names include caustic soda. Sodium hydroxide is often used to manufacture cold processed soaps. It should never touch bare skin, and one must use great care when handling.
Handle with care
If using lye (sodium hydroxide) to make a cold process soaps, always use protective clothing and gear. It is very important to always slowly add lye to water. Never add water to lye, as it will create a caustic eruption. The best procedure is to find a reliable recipe and follow all the steps.