Soap Making Lye Calculator
Soap Making Lye
Calculate the correct amount of lye (sodium hydroxide) and water needed for cold process soap making based on oil weights and SAP values.
Formula
Lye = Oil Weight x SAP Value x (1 - Superfat% / 100); Water = Lye x Water:Lye Ratio; Total Batch Weight = Oil + Lye + Water
Frequently Asked Questions
What is the SAP value?
SAP (saponification value) indicates how much lye is needed to convert one ounce of a specific oil into soap. Each oil has a unique SAP value.
Why do I need superfat?
Superfatting leaves a percentage of oils unsaponified in the finished soap. This makes the soap more moisturizing and provides a safety margin to ensure no excess lye remains.
Is lye dangerous?
Yes, sodium hydroxide is a caustic chemical. Always wear gloves and eye protection. Add lye to water, never water to lye, to avoid a dangerous exothermic reaction.
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