Kusatsu Onsen’s Yubatake: Japan’s Hot Spring Treasure
The Yubatake at Kusatsu Onsen, Japan’s largest hot spring source, disgorges an impressive 4,000 liters of thermal water per minute. Its appellation, “Yubatake,” stems from the practice of guiding hot springs through wooden troughs known as “yudoi,” a process that not only cools the water but also extracts crystalline hot spring elements referred to as “yuno hana.” These “yuno hana” held substantial value during the Edo period, commanding premium prices and even serving as tributes to the shogunate.
Kusatsu Onsen’s Yubatake distinguishes itself with its scorching, highly acidic hot springs and distinctive bathing techniques. The source reaches a searing 55 degrees Celsius, boasting a remarkably low pH level of 2.1, capable of dissolving metals and even affecting the skin. Immersion is not feasible, thus necessitating the exposure of the hot water to air via the “yudoi” to achieve cooling without compromising its essential constituents. Certain lodgings adopt the “time bath” method, involving the draping of a towel over one’s head, a brief immersion in the scalding bath for three minutes subsequent to the enhancement of blood circulation, and the meticulous removal of perspiration. This method optimizes Kusatsu Onsen’s potent bactericidal and detoxification properties, immortalized in musical compositions such as “Kusatsu Yumomi Uta” and “Kusatsu Bushi.”