Determining water content of a soap recipe

by Samantha

As I'm a scientist and I actually enjoy manually calculating lye. But, being new to all of the soap making, I can't find anything that tells you a general rule of thumb even about the water content.

What do you start with? What are the guidelines?

The soap recipe I'm using now (by going backwards in the formula) I've figured used a 37.5% water by weight compared to total weight of oils in recipe (8 lbs oils, 3 lbs water).

Some recipe's are different and I was curious as to where can a new beginner start. I don't wish to use a lye calculator because then I lose the value of going through the "why" of the process through calculating manually.

Any guidance would be valued!
Thank you!


Pick up the book "The Soapmakers's Companion" by Susan Millar Cavitch from your local library. On pages 177/178 she gives a fairly scientific answer to the question "How much water should I use?". In fact, her whole book has quite a bit of information about the chemistry of soap making that would definitely appeal to a scientist.

For beginners it is recommended that you use 38% water by weight of oils. For a batch of soap using 1000 grams of oil this would be 380 grams of water.

As you reduce the amount of water being used in a recipe, the amount of time for the soap to get to trace reduces and the risk of the soap siezing increases. For a beginner, this can get tricky when it comes time to start getting creative by using scents, additives and special techniques like layering and marbling.

Hope that helps,

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water content
by: Anonymous


Thank you so much. I actually have that book and have read it cover to cover and somewhere I forgot about that part (maybe I felt it should have been mentioned again as a reminder after all detailed SAP descriptions at the end of the book). I was attempting to decrease my discount from 15.5 to 10% and determining if I needed to adjust my water. But in fact, no, as my fats & oil weight remain the same.

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