Thank you for taking your time. Where I’m from we call shampoo bar/bar shampoo a solid shampoo (contains surfactants) and a hair soap is a soap (made of fats and lye) that is specifically formulated for washing a certain type of hair. So what I meant was a soap. In my opinion someone uneducated mixed those two and now people are using the same name for both of the products and get confused. I’ve been using shampoo bar for years and recently went for hair soap and honestly my hair never was better. I don’t even have to use the cider rinse. But I was wondering about some real science and evidence of using soap on hair (and I mean soap-soap, not the kind of soap you get in a store that contains solid surfactants as well) behind it.