Superfatting vs. Effective Lye Discounting

By Kelly J. Bloom

First to simplify, "super fatting' is the purposeful unbalancing of a chemical equation.  You normally would balance the lye solution (alkali) to equally match the acids in the oils you are using to a perfect 1:1 chemical balance. That would give you excellent laundry soap, but would not be very emollient to your skin, however.

The object of super fatting is to have your formulation of lye solution and oils set up to be oil heavy, meaning that there will be more oil molecules than lye molecules and the match up bonding will leave excess unused oil molecules free in your soap mixture/soap bars. This is where you get the extra emollient properties of your soap, or some... as the glycerin is a contributor too.  So essentially, super fatting is just making sure you leave a little extra oil free in your soap.  Basically.

There are two ways to do this.  Either one is absolutely fine, or if you set your calculations up right you can theoretically even do both together. It is purely personal choice on how you decide to "super fat", just be sure and use a good calculator and/or SAP values when formulating so you can be precise.

Way 1:  Effective Lye Discount
This is where you do not add extra oils at the trace to create your "super fat' effect. In building in an automatic ELD (Effective Lye Discount) you set up your calculator to create the lye discount you want... 5%, 6%, 7% are the most common values. Lower than 5% without adding additional fats/oils at trace can contribute to a harsher bar, and super fatting over 10% can lend toward the loose oils going rancid faster in time, or even contribute to DOS (Dreaded Orange Spots).  I recommend 6 to 7% to start with.

Anyway, most soaping calculators allow you to set the lye discount/Effective Lye Discount. You plug all your oils in the calculator to be mixed with the lye in the beginning.  The only value that changes the super fat/ELD value is the AMOUNT OF LYE USED. Less lye means the ELD increases to larger numbers (i.e., reducing lye by 1 oz may cause the ELD to go from 6% to 7%). Increasing the Lye lowers the ELD (i.e., increasing lye by 1 oz may cause the ELD to go from 6% to 5%).  You can manually adjust this by changing the lye value in your calculator until you have the % of super fat/ELD that you want your bar to have.

Way 2:  Super fat at Trace
This way you build your formulation up with a small amount of additional (2-5%) to be added at the mid to end of trace time. You set your formulation up with a much lower Effective Lye Discount, sometimes at zero.  Then you add those "extra" oils to the calculator that are to be added at trace, and increase that oils amount until you arrive at the super fat/ELD value you want your bar to end up at.  Using this way of super fatting though, you will use more lye in your formulating.

Follow along with this example of a four-oil recipe (and feel free to use it as a starter recipe):

All amounts are digital weights, not volume.

10 oz Olive Oil
10 oz Coconut Oil
10 oz Shortening
2 oz Sweet Almond Oil
11 oz Water
4.5 oz lye

Now here are examples of what happens to the lye when you add the almond oil with the other oils, and what happens when you add it at the end of trace:

4.5 oz Lye gives a 6% lye discount and in the final bar a 7.6% Effective Lye Discount, or super fat.

But if I do not add that 2 oz of Sweet Almond oil until the end of trace look what happens:

4.5 oz lye gives a 6% lye discount and in the final bar (with Sweet Almond added at end of trace, not with rest of oils) an 11.7% ELD (Effective Lye Discount), or serious SUPERFAT!  11.7 is terribly high. Many oils we use for super fatting have shorter shelf lives and by merit of that can go rancid much faster.  To pull the Effective Lye Discount DOWN a bit, so that the bar is not at 11.7% I must increase my lye value on the calculator!  I must use 4.6 oz of lye instead of 4.5 oz to get that 6% super fat ratio!

Man, I sure hope I have not confused you more now!  :)