Q & A
Frequently Asked Questions
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Where can I find the spring type of a hot spring?
The spring type is listed on the official analysis certificate (温泉分析書) posted inside the bathing area of every onsen facility. You can also check it on my Onsen Techo.
Can the same spring type feel different at different facilities?
Yes. Mineral concentration, water temperature, and whether the water has been diluted all affect the bathing experience. Comparing the key component figures on the analysis certificate reveals the differences.
How Spring Types Are Classified
Spring type is determined by the dominant component in the spring water — a combination of cations (positive ions), anions (negative ions), and dissolved gases gives each spring its official name.
| Spring Type | Key Component / Condition | Typical Characteristics |
|---|---|---|
| Simple thermal spring | Low dissolved solids or temperature ≥ 25 °C | Mild, suitable for everyone. Recognised benefit for insomnia and neurosis |
| Chloride spring | Sodium, calcium chloride etc. | "Heat spring" — warming, antiseptic; body stays warm after bathing |
| Bicarbonate spring | Bicarbonate ions | "Beauty spring" — cleansing, softens skin |
| Sulfate spring | Sulfate ions | Prevents arteriosclerosis; skin-smoothing |
| Carbon dioxide spring | Free CO₂ ≥ 2,000 mg/L | "Heart-friendly spring" — dilates blood vessels |
| Iron-containing spring | Iron ions ≥ 20 mg/L | Anaemia, gynaecological conditions |
| Sulfur spring | Sulfur compounds (hydrogen sulfide type etc.) | Skin conditions, detoxifying; strong sulfur odour |
| Acidic spring | pH < 3 (high hydrogen ion concentration) | Strong bactericidal effect; skin conditions |
| Radioactive spring | Radon and other radioactive elements | Gout, neuralgia, rheumatoid arthritis |
| Iodine-containing spring | Iodine ≥ 10 mg/L | Arteriosclerosis, chronic skin conditions |
References
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