I'm also not terribly concerned with what exactly is left from my super fat. For me it's more just a way to give myself a small insurance policy against being left with a lye-heavy soap. Even the obscenely expensive commercial digital scales are often off by a gram or two even with regular calibration. A gram or two may not make much of a difference in a 10lb batch of soap but if you're doing a 1lb test batch or even a single bar test batch a gram or two very well might mean the rubbish bin or a re-batch...and I detest re-batching.
Usually, if I'm looking to add particular qualities to a recipe that will survive the saponification process I will use cosmetic additives or incorporate an oil with a higher percentage of unsaponifiables such as avocado oil. I actually have a base recipe that only uses lard, CO, OO, and castor and it's one of the best soaps I've ever used. Heck, you could make a mighty fine two oil soap if you have at least a working knowledge of the chemistry behind the curtain and a general idea of what qualities each oil will bring to the table after saponification. When I first started out I spent months researching and learning everything I could about the chemistry of soap making before I even attempted my first batch. Even beyond it being invaluable information to know I also find it incredibly fascinating. I've always really dug chemistry, even as a young child. That's one of the reasons I pursued a career as a chef. Cooking, and especially baking, in its purest form is chemistry. The chefs who practice molecular gastronomy understand the chemistry of food on a much deeper level than most and are thus able to manipulate food in amazing and ingenious ways.
