Making cold process soap successfully requires precise measurements of lye and oil. If too much lye is used the soap will be lye heavy, which can irritate or even burn the skin. Lye heavy soap will have a higher pH than perfectly balanced cold process soap. If you are worried that your soap is lye heavy, there are several techniques to test the pH and discover if it is safe to use on the skin. One of which includes using something you may already have in your fridge…red cabbage!
What is pH and what does it have to do with soap? The pH scale measures how acidic or basic a substance is. The scale ranges from 0 to 14. A pH level of 7 is considered neutral. A pH higher than 7 is considered basic or alkaline, and pH level of below 7 is acidic. Cold process soap is naturally alkaline with a pH of around 9-10. This pH helps to gently clean the skin.