Lye Discount

When using our SBM soap calculators to make liquid soaps, start with specifying "0" as the "superfat" percentage. If using the "advanced" version, you can leave this blank and the program will default to using a 'zero' superfat level.

If one is used to making solid soaps, there's a powerful assumption that superfatting must work the same way in liquid soapmaking, but this is not so.

Solid sodium soap is limited in alkalinity (pH) by adding a bit of extra oil to the formula above what is needed to fully saponify all of the oils used in a given formula. The extra oil-over-lye margin is called "superfat".  Conversely, this same idea can be expressed as 'shorting' the lye amount used so that it's a bit less than the oils suded would need to completely saponify. This leaves some left as oil, not soap and the shortage ove lye-over-oil is referred to as "lye discount". Same idea, just expressed from the opposite point of view.

Here's the difference in applying "superfat" or "lye discount" to solid and liquid soaps:

In solid soaps, the extra oils left in the end product are "soaked" into your soap block just as if it were a solid sponge. The oils have nowhere to go, so they don't separate out and they can contribute to the soap products mildness, etc.

In potassium liquid soap solutions, there's no 'sponge' matrix for any extra oil to be held stable in. Instead, what you have is an unstable mix of liquid soap/water solution and free oils. Since oils and water don't mix or dissolve in each other, the oil separates out as cloudiness and a floating oily 'gunk' layer. For this reason, extra oils as 'superfat' or "lye discount" is not a good idea.

Some people online will insist that they regularly "superfat" liquid soap formulas and get great results. Generally, they are using inaccurate soapmaking calculators and counteracting oil-separation by thickening/emulsifying the final LS solution in other ways.   To some folks, "them is fightin' words, Steve" and arguments can & do fly both ways on this online, but I will strongly say that when using our SBM oils supplies (I've verified their SAP values myself) and using our own SBM soap calculators (I designed & programmed them myself) and our specified LS making methods in the case of our SBM Advanced calculator (hundreds of identical results produced), start with zero superfat (or leave it alone and let the calculator default to zero).

Once the liquid soap is made, you can experiment with adding oil-plus-emulsifier to get a stable liquid soap solution-plus- oil added solution to your liking. (The function of an emulsifier is to 'suspend' oil in water solutions)

If you do want to add superfat in the traditional way by adding extra oil to your formula at the start, use some "Turkey Red" oil. Turkey Red is a modified castor oil (treated with sulfuric acid, actually) that will not saponify at all and is totally dissolvable in water. Turkey Red (named so because of it's use in some old red dye processes) feels like regular castor oil and essentially 'goes straight through' the soapmaking process unchanged. Therefore, you can add it at the start of your process or add it at the very end to your otherwise finished liquid soap solution. I'd recommend the latter, as that way you could add it a drop at a time to a sample to see if you like the results before committing your entire batch to using it.

Having "tossed my gauntlet" on the topic if superfat in liquid soaps, let's please hear from other people, too...