Soap making - where art and science meet.
Hello everyone! I hope you are all well. It’s a pretty day here on the coast and things are starting to dry out from the 2 plus inches of rain we had a few days ago. I’m still itching to get out and play in the dirt, but it’s still frozen and I'll have to be patient a while longer.
So instead let’s talk soap making. Today I’ll give you a quick chemistry lesson because yes there is chemistry involved in the soap making process. Don't worry, I'll make it as brief as possible. I think I fell in love with making soap because it allows my inner science nerd to come out as well as my artistic side.
What is soap? Believe it or not soap is a salt. If you look on a pH scale which runs from 0 to 14, you will see that from 0 to 6 are acids, 8 to 14 are your bases or alkaline, and 7 is neutral; this is where you'll find salts. In soap making, acids and bases are blended together to create salts and glycerin.
To make soap you mix triglycerides (fats and oils which are classified as acids) with sodium hydroxide, also known as lye (which is alkaline). Their molecules bind together creating an exothermic chemical reaction known as saponification. The product of this reaction is raw soap; at this stage it is still quite caustic and has begun to heat up. Once poured into a mold it is insulated with towels to keep the heat in, and left to continue the saponification process known as gel phase. This is where the raw soap naturally heats up and turns into almost a liquid state. It also discolors to a brown which can be alarming but not to worry, all the colors come back after it cools down! As saponification comes to an end, the temperature of the soap starts to drop; this generally takes 24 to 36 hours. (In the photos below you will see the color difference between a freshly poured batch and one going through gel phase).
Once saponification has completed you have a milder product. I generally make soap in the morning hours and remove the loaf from the mold the next morning. Once unmolded, I let the soap loaf sit for a day before I slice it into bars. These bars go onto a rack and cure for 4 to 6 weeks. During the curing process water evaporation takes place while the crystalline structure of the soap is constructed within making a hard bar. (The photo below is a pH test I did on a batch of soap that was almost done curing, notice it is now almost neutral).
Each type of oil has a SAP value; knowing these values is important in figuring out how much lye is needed in your recipe. Too much lye will be harsh on your skin, and not enough lye will leave too many oil molecules running amok, and you’ll have a very soft soap. When I first started making soap, I had to do all the math long hand to figure recipes. Today it’s much easier with the help of ‘soap and lye calculators’ you can find online.
I should also mention there are different types of soap making processes. I use cold process mainly, meaning I pour the oils and lye solution together when they both reach room temperature. There is also hot process soap making, where you work at much higher temperatures and use a crock pot; some people even put their molds in an oven.
Each fatty acid offers different qualities to your soap. For example, coconut oil is high in lauric acid which adds to the cleansing abilities of your soap. However, adding too much to your recipe can create a bar that will strip too much of the natural oil off your skin and leave your skin dry. Olive oil, avocado and rice bran oil all add conditioning properties with their oleic acid values, while palm oil, which is high in palmitic acid, gives a great lather.
There are so many different types of oils and butters available now it can get overwhelming. I try to keep it simple – this keeps the costs down and the ingredient list shorter. I’m a label reader on just about everything and there is nothing that turns me off from purchasing something faster than a long list of ingredients!
I hope you found this post interesting and educational. Like always, if you have any questions leave me a message. In my next post I think I will talk about scent combining so stay tuned!