Sodium Cocoyl Isethionate (SCI) — Frequently Asked Questions

Because they are liquids or pastes and cannot hold bar structure. A bar must be a crystalline solid that can be milled, plodded and stamped and that holds together in use without dissolving away in one wash. SCI is a waxy crystalline solid, which is why it is the backbone of essentially every syndet bar on the market.

Because it is an ester rather than the salt of a fatty acid. Soap must be alkaline, around pH 9 to 10, to function, and that alkalinity swells and disrupts the skin barrier. SCI is stable and effective at neutral or mildly acidic pH, closer to the skin's own surface, so it cleans without the tightness soap leaves behind.

Yes, far better than soap. Soap reacts with calcium and magnesium to form the insoluble scum seen as a bathtub ring and loses its lathering ability in the process. SCI does not form those insoluble salts, so it continues to foam and clean in hard water, which is a practical advantage in much of the world.

Dense and creamy rather than loose and bubbly, with a notably soft after-feel. Users accustomed to sulfate-based products sometimes read that as less effective, when it is simply a different foam structure. Formulators often pair it with a foam booster where a more voluminous lather is wanted for consumer expectation.