We all know that both are great zero-waste alternatives, considering their minimal packaging. However, they are not the same, even if they look alike!
If you ever tried shampoo bars that don’t work, make your hair sticky, or don’t foam, it’s probably because they were soap bars!
The biggest difference is their formulation and their pH.
👉 Soap bars are made with oils and a lye solution (sodium hydroxide + water). I only use vegetable oils to guarantee a vegan product, but soap can be produced in this way (“cold process”) using also animal fat.
After the saponification reaction, the soap will reach a naturally alkaline pH of about 8-10. Our skin is acidic with a pH between 4 and 5.5 but has the ability to restore its natural pH.
👉 On the contrary, our hair cannot do that. Our hair is also acidic, but with a pH of even 3.7! A soap bar’s pH is too high for our hair. Haircare products should have a PH of 6 or lower.
Shampoo bars are not a product of saponification (oils + lye) but they are made using some “detergents” or “surfactants”. They are molecules derived from fats and can give lather and cleansing properties to the shampoo. I always use two surfactants: Sodium Cocoyl Isethionate powder (derived from coconut) and Cocoamidopropyl-Betaine (biodegradable).
Did you know? What is your experience with solid products?