I teach a lot of classes on how to make soap. People are fascinated by the process.
One question I am often asked is, “Can you make soap without using lye?” The simple answer is no, but that doesn’t tell the whole story. The word soap, short for saponification, means a mixture of oils with lye and water. You can make a lot of things without lye, but they aren’t really soap.
Saponification is a process by which triglycerides react with sodium or potassium hydroxide to produce glycerol and a fatty acid salt, called ‘soap.’ When sodium hydroxide is used, a hard soap is produced. Using potassium hydroxide results in a soft soap.http://chemistry.about.com/
First, let’s talk about what lye really is. It is the result of a chemical process of water reacting to being filtered through wood ash. It is a natural product, though a toxic one, at its basic level.
For the second chemical reaction in this process, we blend the lye with water and heat it up to around 170 degrees Fahrenheit before it is ready to use.
Next, we add the cooled lye water into our mixture of room temperature oils. We heat all of the oils together to blend the oils that are liquid at room temperature, like olive oil, with the ones that are solid at room temperature, like coconut oil. This third reaction acts upon the oils, the water, and the lye, turning them into soap. Now the waiting begins. We want the complete reaction to take place before we use this combination as soap on our skin.
The complete process can take up to 8 weeks to be final. When it is done, none of the toxicity of the lye still exists within the soap. The chemical reactions are complete. We also wait so that most of the water has a chance to evaporate and our bar stays nice and solid in the shower.
I hope this helps explain a little bit about the mystery of saponification and lye’s role in the process.