Japanese Onsen & Sauna Guide
Deep dive into onsen spring types, components, and scientific knowledge
Japanese Onsen & Sauna Guide
Deep dive into onsen spring types, components, and scientific knowledge
Japanese Onsen & Sauna Guide
Deep dive into onsen spring types, components, and scientific knowledge
Japanese Onsen & Sauna Guide
Deep dive into onsen spring types, components, and scientific knowledge
26 articles in total
Why do some hot springs look cobalt blue, pale blue, or emerald? Learn how Rayleigh scattering, silica and sulfur colloids, Beppu's Umi Jigoku, and bathing cautions shape the color.
Why do some hot springs look emerald green, yellow-green, or pale green? We break down the causes, including acidic iron, sulfur with hydrogen sulfide, light scattering by sulfur colloids, and algae in channels, based on guidance from Japanese experts.
Why do brown and reddish-brown hot springs look that way? Learn how iron oxidizes in the air, why source water and baths differ in color, plus towel stains, drinking cautions, and what color really means.
What is a clear hot spring? This guide explains why colorless water doesn’t mean weak mineral content. Learn common clear spring types, famous examples like Arima’s gin-sen, what to check on the analysis sheet, and safety notes on heat and salt.
Learn why milky hot spring water looks white. This neutral guide explains how tiny particles scatter light, what causes precipitation, why color shifts, and bathing safety tips.
What is a carbonated hot spring? Learn the standard of 1,000 mg/kg or more of free carbon dioxide set by Japan’s Ministry of the Environment. Discover how tiny bubbles form on the skin, why these baths are served lukewarm, famous hot springs like Nagayu, and the difference between natural and artificial carbonated baths.
What is a radioactive hot spring? Learn the official standard set by Japan’s Ministry of the Environment: radon 8.25 Mache units = 111Bq/kg. Explore famous baths, the science of hormesis, and key safety tips.
What is an iodine hot spring? Learn the official 10 mg/kg iodide standard, 2014 classification changes, sea-derived strata, yellow-brown color, medicinal smell, and thyroid and drinking cautions.
What is an iron spring? Learn the Ministry of the Environment standard of 20 mg/kg or more of total iron ions, why clear water turns reddish brown by oxidation, famous baths like Arima, Nagayu, and Ikaho, and the difference between bathing and drinking it.
Learn how acidic hot springs are defined under Japan’s Ministry of the Environment standards, plus famous baths like Kusatsu, Tamagawa, and Zao, and key cautions for skin, eyes, and wounds.
26 articles in total
Why do some hot springs look cobalt blue, pale blue, or emerald? Learn how Rayleigh scattering, silica and sulfur colloids, Beppu's Umi Jigoku, and bathing cautions shape the color.
Why do some hot springs look emerald green, yellow-green, or pale green? We break down the causes, including acidic iron, sulfur with hydrogen sulfide, light scattering by sulfur colloids, and algae in channels, based on guidance from Japanese experts.
Why do brown and reddish-brown hot springs look that way? Learn how iron oxidizes in the air, why source water and baths differ in color, plus towel stains, drinking cautions, and what color really means.
What is a clear hot spring? This guide explains why colorless water doesn’t mean weak mineral content. Learn common clear spring types, famous examples like Arima’s gin-sen, what to check on the analysis sheet, and safety notes on heat and salt.
Learn why milky hot spring water looks white. This neutral guide explains how tiny particles scatter light, what causes precipitation, why color shifts, and bathing safety tips.
What is a carbonated hot spring? Learn the standard of 1,000 mg/kg or more of free carbon dioxide set by Japan’s Ministry of the Environment. Discover how tiny bubbles form on the skin, why these baths are served lukewarm, famous hot springs like Nagayu, and the difference between natural and artificial carbonated baths.
What is a radioactive hot spring? Learn the official standard set by Japan’s Ministry of the Environment: radon 8.25 Mache units = 111Bq/kg. Explore famous baths, the science of hormesis, and key safety tips.
What is an iodine hot spring? Learn the official 10 mg/kg iodide standard, 2014 classification changes, sea-derived strata, yellow-brown color, medicinal smell, and thyroid and drinking cautions.
What is an iron spring? Learn the Ministry of the Environment standard of 20 mg/kg or more of total iron ions, why clear water turns reddish brown by oxidation, famous baths like Arima, Nagayu, and Ikaho, and the difference between bathing and drinking it.
Learn how acidic hot springs are defined under Japan’s Ministry of the Environment standards, plus famous baths like Kusatsu, Tamagawa, and Zao, and key cautions for skin, eyes, and wounds.