Lye concentration vs. water-to-lye ratio
Two valid ways to describe the same lye solution—and the conversion that prevents costly confusion.
Both describe the lye solution
Lye concentration is alkali weight divided by alkali plus water. Water-to-lye ratio is water weight divided by alkali weight. They describe the same two quantities from different angles.
A practical example
A 33% lye concentration means 33 parts alkali in 100 parts solution. The equivalent water-to-lye ratio is about 2.03:1. For 100 g alkali, that is about 203 g water.
- Concentration = lye ÷ (lye + water) × 100.
- Water-to-lye ratio = water ÷ lye.
- Ratio = (1 ÷ concentration as a decimal) − 1.
Why water as percent of oils behaves differently
Water as percent of oils bases water on oil weight rather than actual alkali demand. Two formulas with the same oil weight can require different lye, so the resulting solution concentration changes.
Use one method consistently
Choose the method you understand, record it with its value, and compare formulas using the same basis. Confirm that reactive liquids or additives are handled explicitly rather than silently altering the solution.