A refreshing mint soap bar for hair and body, from Natura Siberica's men's range.
The thing worth knowing about washing hair with soap
This matters, and almost nobody explains it.
Soap is alkaline — typically around pH 9 to 10, because that is simply what saponification produces. Hair and scalp are acidic, around pH 4.5 to 5.5. And the hair cuticle — the overlapping scales that make up the outside of every strand — lies flat in acid and lifts in alkali.
Which means soap on hair does two things: it cleans it very effectively, and it leaves the cuticle raised, so the hair can feel rough, tangle more easily and look duller. In hard water there is a second effect: soap reacts with dissolved calcium to form a film — the same scum you get in a bath — which coats the hair and weighs it down.
None of that makes soap unusable on hair. It is what everybody used before shampoo existed. But there is a traditional fix, and it works: an acidic rinse afterwards. A tablespoon of vinegar in a jug of water, poured over the hair and rinsed out, restores the acidic pH, closes the cuticle back down and dissolves any soap film. The smell disappears as the hair dries.
It is worth noting that most products sold as "shampoo bars" are not soap at all — they are solid detergent bars formulated at hair-friendly pH. If your hair reacts badly to soap, that is the alternative.
On the body
No such complication. Skin handles a soap bar perfectly well, and mint gives a genuine cooling sensation — menthol triggers the same cold receptors that respond to low temperature, which is why it feels cold without changing your temperature at all.
Making it last
Keep it out of standing water. A bar left in a puddle absorbs water, goes soft and dissolves. Use a draining dish and let it dry between uses.
Note
Avoid the eyes — mint stings. Rinse with water if it gets in.