Shampoo soap and Shampoo bar are not the same thing. Shampoo soap is made through saponification and has a high pH of around 9-10, which can leave hair dry and coarse. A Shampoo bar is solid shampoo made with a different formula from soap, and its quality varies greatly depending on the manufacturer. FOAM’s Shampoo bar is pH-balanced and formulated with a gentle, sulfate-free surfactant derived from coconut.
It’s understandable that the terms get mixed up. Both are solid hair-washing products, and in everyday speech, shampoo soap is sometimes used as a generic term for all solid shampoo products. But the difference in chemistry and effect on hair is significant, and explains why experiences with solid shampoo products can differ so markedly.
Shampoo soap, Shampoo bar, and liquid shampoo: here’s how they differ
| Feature | Shampoo soap (saponified) | Shampoo bar | Liquid shampoo |
|---|---|---|---|
| Manufacturing | Saponification of oils | Solid format; varies by manufacturer | Liquid formula with water |
| pH level | High, around 9-10 | Varies by formula | Varies by formula |
| Surfactants | Soap salts | Varies; sometimes sulfates | Often SLS or SLES |
| Effect on the cuticle | Swells it, leaving hair dry | Depends on pH and surfactants | Varies |
| Adjustment period | Often yes | Depends on formula | Rarely |
| Suitable for all hair types | No | Depends on formula | Depends on formula |
Why does pH matter so much for hair?
The hair cuticle, the outermost protective layer of each hair strand, needs a slightly acidic environment, around pH 4.5-5.5, to stay closed and smooth. Saponified shampoo soap has a pH of around 9-10. This causes the cuticle to swell and open with every wash, leaving hair feeling coarse, dry, and more prone to frizz.
The pH of Shampoo bars also varies depending on the manufacturer and formula. FOAM’s Shampoo bar is formulated to be within the right pH range from the start, so the cuticle retains its natural closed state and hair feels soft straight out of the shower. Learn more about how to wash your hair properly in our guide to using a Shampoo bar.
How can you recognize a good Shampoo bar?
Looking at a solid shampoo product and wondering if it’s worth trying? There are three things to look for. The ingredient list tells you a lot: choose a Shampoo bar with mild, sulfate-free surfactants and avoid products containing soap salts (Sodium Cocoate, Sodium Palmate) or sulfates such as SLS. A good-quality Shampoo bar will also state that it is pH-balanced.
FOAM’s Shampoo bar cleanses with a gentle, sulfate-free surfactant derived from coconut and is pH-balanced to suit hair’s natural environment. Learn more about what sets the different options apart in our guide to the best Shampoo bar, and if you want to compare it with liquid shampoo, read more in our article on shampoo soap vs. liquid shampoo.
Tips from foam.nu: Have you tried a solid shampoo product and found that your hair became dry or brittle? It was probably a saponified shampoo soap with a high pH, or a Shampoo bar containing sulfates. Not all solid shampoos are created equal.
For an overview of all shampoo options, both solid and liquid, read our complete guide to Shampoo bars and our shampoo guide.