The ingredient with a dozen names, Deionized Water
Deionized water is also known as DI water, DIW or de-ionized water. It is also synonymous with demineralized water or DM water. These different names all refer to water that has been treated and had almost all of its mineral ions removed. For example, cations like sodium, calcium, iron, and copper, and anions such as chloride and sulfate are virtually absent in DI water.
Why Use Deionized Water In Formulas?
Deionized water is the preferred water for cosmetic formulas because virtually all ions are removed. That means that the water will be a clean canvas for water-based formulas. So It is ideal for all water bases cosmetic bases such as lotions and sprays so no trace ions will affect the base. Using DI water instead of distilled water is preferred in cold process soap. That ensures that no calcium, copper, or iron will react with the lye.