Oils are fats. Some are liquid at room temperature (what we typically call oil) and some are solid at room temperature. The base oils are the oils that are reacted with lye to create soap, and not all oils are created equally! There are animal fats and vegetable fats. Minimally processed fats, and fats that require prolonged chemical processes to produce them.
After making my first few batches of soap using recipes I found on the internet I decided it was time to start creating my own that provided the benefits I was looking for. Being the geek I am, however, I found that just letting someone tell me what an oil did wasn’t good enough for me. I needed to know the chemical ‘why’ behind the oil selections.
In order to do that I needed to do a little research. I found each fat (oil) was a combination of different fatty acids, and each acid behaved a little differently when reacted with the lye. This accounts for the differing amount of lye used in the recipes you may find either in books or on the internet. Here is a chart of the fatty acids and the benefits they bring to soaps:
So why do I want all this information? I can compare the properties of oils used in recipes and replace them as I feel fit. For instance, if I find a recipe that uses walnut oil and I know my customers are allergic to walnuts I could swap it out with an oil that has a similar fatty acid composition. Looking at the chart, I would replace the walnut oil in the recipe with pumpkin seed oil or sunflower oil. As I have mentioned before, soap making is a chemical process. There MUST be a correct balance of lye to fats. Any time you make a change to your recipe (especially when swapping oils), make sure you run your recipe through a lye calculator. My favorite is the calculator on SoapCalc.net.
I hope this helps you start your journey in SOAP!!