spent lye

chemical solution

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July 14, 2026

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Spent lye is the alkaline, glycerol-containing liquid that results from saponification, a process where fat is boiled with a lye solution in soapmaking. After cooling, this liquid is drawn off from the floating curd. Lye itself is a strong alkaline solution, historically leached from wood ashes and used for making soap and washing. It can also refer to a strong solution of sodium hydroxide or potassium hydroxide.12

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soap and detergent
Boiling process
…slightly alkaline salt solution, termed spent lye, is extracted from the bottom of the pan or kettle and subsequently treated for glycerin recovery.
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…slightly alkaline salt solution, termed spent lye, is extracted from the bottom of the pan or kettle and subsequently treated for glycerin recovery.
Read More