山中湖平野温泉 石割の湯
Yamanakako Hirano Onsen Ishiwari-no-YuOperated by · 森トラスト・ホテルズ＆リゾーツ株式会社
- Color
- faintly yellow-brown, slightly turbid
- Taste
- tasteless
- Odor
- sulfurous
Sodium Carbonate-Sulfate-HSiO3 spring
- Sodium Na⁺
- salt's cation — pairs with chloride to make the water salty.
- Carbonate CO₃²⁻
- strongly alkaline; slippery feel.
- Smooth skindry, rough skin
- Recoveryfatigue, stress
Yamanakako Hirano Onsen's Ishiwari-no-Yu is a simple thermal spring, but a strongly alkaline one — pH 10.6 at the wellhead gives it a pronounced slippery feel on the skin and places it squarely in Japan's beauty-water family. Dissolved solids are light at 157 mg/kg, so the water is gentle rather than assertive, though at the source it carries a faint yellow-brown tint with slight turbidity and a light sulfurous note. The attached indications panel lists autonomic nervous system instability, insomnia and depressed mood among the spring-type indications, framing this as water for winding down. The source emerges at only 26.8 °C, so the bath is reheated; the public posting adds that the water is also diluted, recirculated through a filter and chlorine-disinfected before it reaches the tub.
Sampled at wellhead·Analyzed Oct 1, 2025·株式会社山梨県環境科学検査センター·Cert no. 山環温第2025-8号