About Black Water
As the name suggests, the black beauty water temperature spring at Take-no-yu is blackish-brown like coffee. This is due to the dissolution of substances (peat) from ancient plants, mud from the ocean floor, and volcanic ash into the groundwater. So, does it get dirty like mud? No, it is not. The color of the Kuromi spring is "clear black-brown. It is not muddy, but clear. Since it is completely dissolved in water, it does not precipitate or stick to the body.
Incidentally, Take-no-yu also uses groundwater for the clear water/water coming out of the calan. If you feel your hair or skin creaks when bathing with tap water, please give it a try! There is no difference at all!
The popular thing to do in the bathroom is to get a glass of this black beauty water and put it on your face after washing your face.