There are a lot of posts on here with people throwing around the word "superfat" and from the context it is clear that people are not entirely sure of what the word means in regards to cold process soap. A lot of people talk about superfatting like it's a fancy technique when really it's probably something you've been doing all along and just didn't know it! So I have created this thread to clear up some confusion.
Figure 1.1: Majestic Mountain Sage's Lye Calculator Screen
For the purposes of this thread, I threw together a recipe that is 20 oz. of coconut oil, 20 oz. of olive oil & 10 ounces of palm oil. It was all I could think of on the fly, don't take it as an actual recipe, lol. Let us continue:
Defined: Superfat (synonymous with the phrases "excess fat" & "lye discount") is, quite simply, where there is more oil than lye can "consume" during the saponification process and the soap has excess oil. The golden standard for superfat is 5%. So on the above screen, 7.42 oz. of lye will give you 5% superfat. On most lye calculators, when you enter in a recipe, it will automatically feed you this 5% range because it's the most common and workable range, however anything in the "green" range above is workable and considered to be "good."
**Anything BELOW 5% (the bright red blocks above) and you run the risk of your soap being lye heavy. Unless you have done the recipe before at <5%, avoid those %'s!! I have a recipe that calls for the 1% range and even I eschew that for 5%! **
Let's say you want to go over
5% superfat and soap at the 7% range. There are two ways to do this. One, you can add excess oil, generally done at light trace. In this case you'd add maybe 1-2oz. of extra olive oil at trace. Or, you can use less lye (always follow the numbers on a lye calculator! Don't just start subtracting lye, lol
). Since 5% calls for 7.42oz. of lye, if you cut it back to the 7% range, 7.26oz, there will be less lye to consume the oils and your bar will be a little softer, but more moisturizing on your skin.
If you notice, MMS's lye calculator only goes to 10% (the blue range). The reason is that while superfatting soap makes very moisturizing, mild bar of soap, it also makes a very soft bar that is prone to rancidity. All of that excess oil is unsaponified which means it's basically free-standing. The more free-standing oil, the more iffy the shelf-life. Also, the more prone to DOS (dreaded orange spots) is your soap. Very few people will suggest soaping over 10%. While I am a big fan of Susan Miller Cavitch, I do disagree with her suggesting that you go as high as 15%. It just seems like courting disaster to me.
Okay, so let's say you accidentally
superfat at 10%+. I did once make a batch at 17% superfat by putting in 12 oz. too much of olive oil because math and I are not friends. DO NOT PANIC! The soap is going to be very, very soft. Generally so soft that you may want to leave it in the mold for a couple extra days before cutting. Normally soap needs about 3-6 weeks to cure and allow for excess moisture to evaporate, but anything over 10% will probably need 6-8 weeks to cure. While it will never get rock hard, it will get harder than the fudgey mess you are most likely dealing with.
I will add more to this as it comes to me, but in the meantime I wanted to start the thread and get some opinions on the matter and all that jazz. Questions, comments, etc.