Onsen chemistry extremes
Onsen at the extremes
The most striking springs in the catalog, by the numbers on their certificates.
Hottest sources
Temperature at the wellhead.
- 1Tocen GoshobohHyogo · Chloride100.5°C
- 2Hotel HanakoyadoHyogo · Iron-bearing100.5°C
- 3Tamatebako Open-air OnsenKagoshima · Chloride100.4°C
- 4Oedoonsen Monogata MasuyaMiyagi · Chloride100.0°C
- 5Jigokubaru OnsenOita · Chloride99.8°C
- 6KamioboHyogo · Chloride99.4°C
- 7Kin no Yu Hot SpringHyogo · Chloride99.4°C
- 8Odoriko Onsen KaikanShizuoka · Chloride99.3°C
- 9Mine Onsen Daifunto ParkShizuoka · Chloride99.3°C
- 10Ooedo Onsen Monogatari KounkakuMiyagi · Sulfate98.8°C
- 11Ko Sanso KanoHyogo · Chloride98.6°C
- 12Grandvrio HotelToyama · Simple98.3°C
Most acidic
Lowest pH, into battery-acid territory.
- 1Manza Kogen HotelGunma · Acidic1.50pH
- 2KamiyuYamagata · Acidic1.60pH
- 3Sainokawara RotenburoGunma · Acidic1.70pH
- 4Genshichi Roten no yu Zao OnsenYamagata · Acidic1.70pH
- 5Goza no YuGunma · Acidic1.70pH
- 6Ryokan YoshidayaYamagata · Acidic1.70pH
- 7ShimoyuYamagata · Acidic1.70pH
- 8Wald BergYamagata · Acidic1.80pH
- 9Takamiya Jurin HotelYamagata · Acidic1.80pH
- 10ONSEN & STAY OAKHILLYamagata · Acidic1.80pH
- 11KawarayuYamagata · Acidic1.90pH
- 12Takamiya Ryokan MiyamasoYamagata · Acidic1.90pH
Most alkaline
Highest pH, the silky beautifying waters.
- 1Fuji Marriott Hotel Lake YamanakaYamanashi · Simple10.60pH
- 2Tenkei Izumi Shirane TōGen Ten Emi 閣Yamanashi · Simple10.40pH
- 3Tsukuba EdoyaIbaraki · Simple10.30pH
- 4Yamato Temmokuzan OnsenYamanashi · Simple10.20pH
- 5Nanki Susami Onsen Hotel BellvedereWakayama · Sulfur10.10pH
- 6Ryokan ShirasagiWakayama · Sulfur10.10pH
- 7Rivage Spa HikigawaWakayama · Simple10.10pH
- 8Enzan Onsen KouchisouYamanashi · Sulfur10.10pH
- 9Hotel Mount FujiYamanashi · Simple10.00pH
- 10Tsutsumigawa Hot SpringYamanashi · Simple10.00pH
- 11Shin Inago Gawa Onsen Yū･TorioShizuoka · Chloride10.00pH
- 12Yamanakako Onsen Benifuji no Yu hot springYamanashi · Simple10.00pH
Strongest brine
Most dissolved solids.
- 1Ko Sanso KanoHyogo · Chloride44.0g/kg
- 2Tocen GoshobohHyogo · Chloride37.6g/kg
- 3Hotel HanakoyadoHyogo · Iron-bearing37.6g/kg
- 4Fukuro no YuWakayama · Iron-bearing36.9g/kg
- 5KamioboHyogo · Chloride36.1g/kg
- 6Kin no Yu Hot SpringHyogo · Chloride36.1g/kg
- 7Tamatebako Open-air OnsenKagoshima · Chloride34.2g/kg
- 8Kinokuni OnsenWakayama · Chloride32.2g/kg
- 9Izumi Tenku no Yu Ariake GardenTokyo · Iodine-bearing29.8g/kg
- 10Century Marina HakodateHokkaido · Chloride27.6g/kg
- 11Arima GyoenHyogo · Chloride26.1g/kg
- 12Ojiro No YuYamanashi · Chloride25.5g/kg
Most carbonated
Free CO₂, the fizz on your skin.
- 1Hanayama Onsen Yakushi No YuWakayama · Chloride2,631mg/kg
- 2Lamune OnsenOita · Bicarbonate1,400mg/kg
- 3Hanairo Hot SpringOita · Carbonated1,130mg/kg
- 4Katsuragionsen HappunoyuWakayama · Carbonated1,094mg/kg
- 5ShichihoukanGifu · Carbonated1,042mg/kg
- 6Shichirida Onsen Konoha-no YuOita · Carbonated1,010mg/kg
- 7Gin no Yu Hot SpringHyogo · Carbonated1,010mg/kg
- 8Sui Jin NomoriOita · Iron-bearing989mg/kg
- 9Kawa No Eki Sen Koya Koi Bo Taru Onsen KanFukuoka · Bicarbonate921mg/kg
- 10Hinode Onsen Kinoko no SatoKagoshima · Bicarbonate836mg/kg
- 11Negiya RyofukakuHyogo · Iron-bearing834mg/kg
- 12Ryokan HanamusubiHyogo · Chloride755mg/kg
Highest radon
Radioactive springs studied for joint pain.
- 1Ryokan HanamusubiHyogo · Radon2,240Bq/kg
- 2Taikou no YuHyogo · Radon2,240Bq/kg
- 3KokiHyogo · Radon1,900Bq/kg
- 4Gin no Yu Hot SpringHyogo · Radon1,060Bq/kg
- 5Arima GyoenHyogo · Radon554Bq/kg
- 6Chomei-ji Onsen - Amahanoyu Hot SpringShiga · Radon330Bq/kg
- 7Torikai RyokanTottori · Radon274Bq/kg
- 8ShikimatsuriOsaka · Radon237Bq/kg
- 9Matsuba Onsen Taki-no-yuOsaka · Radon237Bq/kg
- 10Tosenkyo Onsenkan ToshokaSaga · Radon221Bq/kg
- 11Iyonotojiba KisukenoyuEhime · Radon183Bq/kg
- 12Kotohira Onsen KotosankakuKagawa · Radon166Bq/kg
Most silica
Metasilicic acid, a natural moisturizer.
- 1Jigokubaru OnsenOita · Chloride734mg/kg
- 2Maeda onsenOita · Chloride685mg/kg
- 3NetsunoyuOita · Chloride685mg/kg
- 4Kannawa Steam BathOita · Chloride685mg/kg
- 5ShibunoyuOita · Chloride685mg/kg
- 6Tamatebako Open-air OnsenKagoshima · Chloride588mg/kg
- 7Oniishi No YuOita · Chloride584mg/kg
- 8ShouninyuOita · Chloride566mg/kg
- 9Sainokawara RotenburoGunma · Acidic528mg/kg
- 10Goza no YuGunma · Acidic528mg/kg
- 11Yumotoya RyokanOita · Acidic396mg/kg
- 12Ooedo Onsen Monogatari Premium Hotel FugetsuOita · Chloride387mg/kg