I'm the owner and maker of soaps for our family run business, The Natural Bar Soap Company. It's important that the oils you use to make your soap are fresh- and absolutely not rancid. Rancidity is the equivalent of "spoiled" and will produce soaps that are spoiled as well.
Rancid oils could cause your finished bars to smell bad, look bad, and potentially cause skin reactions. Additionally, rancid oils can cause DOS ("Dreaded Orange Spots") in finished bars. It would be a shame to go to all of the work of making soap, only to have it not be useable.
Hope that was helpful!
years of soapmaking, chemistry degree
· 9 years ago