Liquid Castile soap can clean hair, but I would not assume that it will feel like a conventional shampoo. In the workshop, the main qualification is its alkaline character: the demonstrated liquid soaps have a pH that can feel high for hair, particularly longer or rougher hair.
Cleaning hair is not the same as conditioning it
The question is not simply whether Castile soap can remove dirt from hair. It can be used as a hair cleanser. The more important practical question is how the hair feels afterwards. On longer or rougher hair, the result may not feel smooth or conditioning.
Who might still choose to use it?
Small children or people who personally like the result may still choose Castile soap for hair. The workshop does not present the product as universally unsuitable. Instead, it emphasizes that the experience is different and that individual preference matters.
Why not simply lower the pH?
It may seem logical to lower the pH so that the Castile soap behaves more like a shampoo. I specifically caution against that approach in the workshop. Lowering the pH is described as causing the soap system to split rather than remain as a stable liquid soap.
Do not judge it by conventional shampoo expectations
This is a useful example of why different cleanser systems should not automatically be expected to behave the same way. Castile soap is an oil-based soap. If it is used on hair, judge it by the way the hair actually feels after washing rather than assuming that a liquid cleanser must deliver the same smoothness and conditioning associated with a conventional shampoo.
The practical takeaway is simple: Castile soap may be used on hair, but hair feel is the deciding issue. If smoothness and conditioning after washing are important, do not assume that an alkaline liquid soap will provide the same experience as a conventional shampoo.
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