Sodium Hydroxide

Sodium hydroxide, also known as caustic soda or lye, is a highly versatile substance used in a variety of manufacturing processes to make for example. SOAP

This solution, when mixed with fats and oils, will cause a chemical reaction called saponification. The result of saponification is beautiful handmade soap.

sodium hydroxide is a highly alkaline ingredient used in small amounts in cosmetics to establish and hold the pH of a product. 

Sodium hydroxide, with the formula NaOH, is usually used in products as a pH adjuster. It's also used in soap-making to turn fats and oils into soap.