I have been using Brambleberry

lye calculator and adding a superfatting percentage of 5%. I thought this automatically superfatted my recipe.

Now i am wondering if i have been doing it all wrong and i have to add 5% extra oils. I have made quite a few batches and they all pass the zap test, but as i am wanting to sell my soaps i am now panicking that they may be too harsh:???: could someone explain this for me please.

many thanks.

What tends to get overlooked in these discussions, even by experienced soapers, is that you don't know what amount of superfat you'll end up with.

Exact superfat percentages are found in commodity soap. In an industrial process they can superfat pre-made soap by adding fatty acids, acidifying it another way, or adding oil. Since they are starting with essentially pure soap and modifying it in a precise way, the exact superfat percentage is a simple calculation.

It's hard to say how close handcrafters come to the superfat percentages they expect. I believe there are wide variations, and that discussing it in terms of precise percentages is kind of an exercise in imagination.

When you plug a 5% superfat into a

lye calculator, the term superfat is a misnomer. What you are plugging in is properly called a lye discount. A lye discount is a percentage of caustic that you subtract from the calculated amount. The first reason for doing that is because the calculated amount is only an estimate, so you need a lye discount to make sure that you aren't using too much. It's a safety margin.

A

lye calculator estimates the amount of caustic you need by using average saponification values for the oils in your recipe. The REAL saponification values for the oils your supplier sold you should fall within a certain range, but might be significantly higher or lower than average. If they are on the low side and you don't use a lye discount, you could make overly alkaline soap.

The first objective of the 5% lye discount is to help ensure that your actual superfat is 0% or higher. You can expect that it will be greater than zero because a 5% lye discount is a reasonable safety margin for a multiple-oil soap, and the strength of your caustic is probably less than 100%. If instead you use a 10% lye discount, you will have a larger superfat. However, the actual superfat percentage is pretty uncertain.

If you calculate an HP batch with no lye discount and then add oil after the cook, that is the handcrafters' form of superfatting, but the same uncertainty applies. You can add shea butter that remains entirely intact in the soap, or it could get saponified to some unknown extent.