Why Is Lye Used in Soap? (And Why There’s None Left in Your Bar)

If you’ve ever looked into natural soap making, you may have come across the word lye, and wondered if it’s something to be concerned about.

It’s a completely valid question, and one I hear more often than you might think.

The truth is, all real soap is made using lye. Without it, soap simply wouldn’t exist.

When lye (sodium hydroxide) is combined with oils and butters, it begins a process called saponification. This is the chemical reaction that transforms those ingredients into soap and naturally occurring glycerine.

During this process, the lye and oils completely change, creating something entirely new. It’s a bit like baking a cake, the raw ingredients transform completely into something new.

Soap makers carefully calculate the exact amount of lye needed for this reaction, often formulating recipes with a small excess of nourishing oils. This is known as “superfatting,” and it ensures the final bar is not only free from lye, but also gentle and conditioning on the skin.

By the time the soap has fully cured, the lye has been completely used up in the process, leaving behind a mild, skin-loving bar of true soap.

This is how traditional cold process soap has been made for generations.

For me, this method is all about intention. Thoughtfully choosing nourishing oils, allowing each bar the time it needs to cure, and creating something that offers a small, gentle moment of care in your day.

So while the word lye can sound a little intimidating at first, it’s simply part of the transformation that makes true soap what it is.

A quiet bit of science, turned into a small, everyday ritual of care. 

Kelly 🖤