Makuiwa Onsen Hotel Shiga Sunvalley

An on-site source at Shiga Kogen's Makuiwa Onsen. A genuinely hot spring at 71.2 °C, classified as a simple sulfur water — neutral pH, lightly mineralized at 259 mg/kg total solids. The sulfur side shows clearly: HS⁻ and free H₂S together at roughly 11 mg/kg, enough to give the characteristic rotten-egg note. A generous 73.2 mg/kg of metasilicic acid layers in a smoothing silica film, while the overall composition stays soft rather than aggressive — among Japan's hotter natural sources, but gentle in body.

Analyzed Dec 22, 1994·長野県衛生公害研究所