Distilled water is essential in soap making. It is used to dissolve lye, which is necessary for the saponification process that transforms oils and fats into soap. Using distilled water ensures that no impurities or minerals interfere with this chemical reaction, resulting in a more consistent and high-quality product. Unlike tap water, which may contain contaminants, distilled water is pure and does not affect the soap's texture, appearance, or shelf life. Compared to spring or purified water, distilled water offers the highest level of H₂O purity, making it crucial for creating gentle and skin-friendly soaps. By choosing distilled water, soap makers can produce a purer and more reliable soap.