What Is Superfat (Lye Discount)?

Superfat (also called lye discount) is the percentage of oils intentionally left unsaponified in your soap.

Why it matters

A superfat means there's always a little more oil than the lye can react with — so you never end up with excess, skin-burning lye, even if your measurements are slightly off. Those free oils also make the bar gentler and more conditioning.

How much?

5% is the common all-purpose default. Use 1–3% for a harder, longer-lasting bar or salt/laundry soap, and 6–8% for a more moisturizing facial or shampoo bar. Going above ~10% risks a soft, quick-to-spoil bar.