Which alkali is your table talking about
A saponification value is grams of alkali per gram of oil, and there is no universal agreement about which alkali. Analytical tables print it as milligrams of potassium hydroxide per gram — olive comes out somewhere near 190 in those. Soap-making tables usually print a decimal for sodium hydroxide instead, and olive is near 0.134 there. The two describe the same oil. They differ by 1.403, which is the ratio of the molar masses, and nothing about the numbers on the page tells you which one you are looking at.
Read 0.190 as a sodium hydroxide figure and the batch gets 40 percent more alkali than the oils can consume. That is why the first field on the form asks which form your numbers are in rather than assuming, and why the ratio itself is an editable field: if the table you work from states a different figure, use theirs.
Superfat is subtraction
The blend in the form — 45 percent olive, 25 coconut, 20 palm, 5 castor, 5 shea, on 1,000 grams of oils — has a weighted average of 0.1471 grams of sodium hydroxide per gram, so the oils could take 147.1 grams. At 5 percent superfat the page asks for 139.7 instead. The 7.4 grams that came off is the whole of the superfat, and it leaves the alkali equivalent of 50 grams of the blend with nothing to react with.
Nobody adds oil. The commonest way to get this wrong is to cut the alkali and then pour in extra oil at the end as well, which runs the superfat twice and lands at roughly ten percent when the recipe said five.
Three ways of saying water, and they are not the same number
Take that same batch. Read 33 as a lye concentration and the water is 283.6 grams, because the alkali has to be 33 percent of the solution. Read 33 as a percent of the oils and the water is 330 grams. The gap is 46.4 grams on a small batch, which is not a rounding difference — it is a noticeably different recipe.
The page computes whichever convention you name and prints the other two beside it, because recipes get written down in all three and none of them carry a label. Worth noticing: they do not track each other. Hold the water at a fixed percent of the oils and raise the superfat, and the lye concentration falls even though nothing called water was touched, because the alkali shrank and the solution is alkali plus water.
What the page cannot know
Every saponification value here is one you typed. Published tables disagree with each other by a percent or two, and they are averages of a natural product that varies between crops, mills and seasons, so the honest figure for the drum in your workshop is the one on its paperwork. Where a supplier quotes a range, the two ends give two different alkali weights and the page will give you both.
It also has nothing to say about whether a recipe is any good. Superfat levels, water settings and fragrance rates are decisions, and this page does arithmetic on the decisions you have already made. It states no value as fact, issues no verdict, and knows nothing about labelling rules, which vary by jurisdiction and change.
The hazard, named
Sodium hydroxide and potassium hydroxide are caustic. They burn skin and permanently damage eyes, and alkali meeting water gives off heat on its own. There is no procedure anywhere on this page — no order, no temperature, no handling step — and none should be inferred from it. That belongs to the safety data sheet for the material you bought and to whoever taught you the work.
Questions people ask
Why does my lye calculator disagree with this one?
Almost always the saponification numbers, and occasionally the water. Two tables can quote olive at 0.134 and 0.135 and the alkali comes out different in the third decimal; that is real variation in a natural oil rather than an error in either. The larger discrepancies come from the water: a page that assumes a lye concentration when you meant a percent of the oils will differ by tens of grams, which on the blend in this form is 46.4 grams on a 1,000 gram batch.
What is the difference between a SAP value for NaOH and one for KOH?
A factor of about 1.403, which is the ratio of the two molar masses. A table in milligrams of KOH per gram is the analytical convention and reads near 190 for olive; a soap table for sodium hydroxide reads near 0.134 for the same oil. Both describe the same thing. The form asks which form yours is in because reading the wrong column is a 40 percent error in the alkali, and it is silent.
Does superfat mean adding extra oil?
No. It is a reduction in the alkali. On the blend in the form the oils could take 147.1 grams of sodium hydroxide, and 5 percent superfat means weighing 139.7 instead. The oil weight does not change at all. Anyone who both cuts the alkali and adds oil at the end has applied the superfat twice.
Is 33 percent water the same as a 33 percent lye concentration?
No, and the difference is large. On 1,000 grams of oils at 5 percent superfat, 33 percent lye concentration means 283.6 grams of water; 33 percent of the oils means 330. The page prints all three conventions for whatever you enter so you can tell which one a written recipe meant, and the ratio of water to alkali as well, since some recipes are written that way instead.
Do I need to allow for the purity of my lye?
If your supplier states one below 100, yes, and the page divides by it. Flake potassium hydroxide is often sold under 100 percent, and the shortfall has to be made up in weight or the batch is short of alkali. The figure comes from the assay for what you bought, not from here.
Where do I get saponification values?
From whoever sold you the oil. They publish tables, and the number for the specific drum is on its documentation. This page states none, defaults included: the values sitting in the fields are placeholders to replace with yours, and they are there to show the shape of the arithmetic rather than to be used.