Castile Recipe #2
Castile Recipe #3
Castile Recipe #4
Olive oil was probably one of the first non-animal-based oils used to make soap. Castile soap is reputed to have originated in Castile Castle as early as 1567.
Many soap purists will say that to truly be "Castile" soap, it has to be made from 100% olive oil. Technically, I suppose they are right. And while you certainly can make soap from 100% olive oil, I don't really like the lather it makes. Some will describe it as "smooth and creamy," but most will describe it as "slimy."
I encourage you to try it at least once...but just know that the lather is different that what you're probably used to.
Why, you may ask, is the lather different? Each oil in a soap recipe contributes different qualities to the soap. A one-oil soap (like Castile) will have just the soap qualities of that oil - a blend of oils gives you a blend of qualities. The art of creating a basic soap recipe is the art of balancing the various oils all together.
That said, most people make "Castile Soap" with predominantly olive oil, but add other oils in to help balance out the bar. Here are four basic recipes using mostly olive oil. Follow them as written, or just use them as a guide. They will all be slightly different, as the ratio of oils is slightly different. But rest assured, they all make great soap!
More information on which olive oil to choose/use for making soap.