Soap is a byproduct of a chemical reaction that takes place between oils or fats and sodium hydroxide or lye. When mixed with water and then with oils or fats a process called saponification takes place. The initial saponification process takes anywhere from 20 – 90 minutes. After the soap mixture is poured into a mold the rest of the saponification takes place and can take from 5 – 6 weeks. Once the soap has cured it can be tested for proper ph levels using a test strip. You are looking for a ph level of 8 – 10.5.
Each oil has a different SAP value which determines the amount of lye it will take to convert that oil into soap. If you mix oils you will need to calculate a blended SAP value. Programs like our Soap-Calc spreadsheet can help you do this.