Centuries-old unique bathing style
At Kusatsu Onsen, one of Japan's most famous hot springs, a cultural tradition known as yumomi has been practiced since the Edo period. This method of stirring the hot spring waters was devised so that bathers could fully enjoy the wealth of therapeutic benefits that Kusatsu's hot springs have to offer.
Hot spring source too hot
According to Japan's Hot Springs Act, any spring hotter than 25 degrees can be called a hot spring, but the source of many of Kusatsu's hot springs range between 50°C and nearly 90°C. For this reason, the temperature of the water must be lowered. However, cooling the hot spring with cold water diminishes its therapeutic effects.
Yumomi is therefore an ancient technique that serves the double purpose of lowering the water temperature without diluting it.
Purpose of yumomi
In addition to enjoying the healing effects of the hot spring water at the optimal temperature, the act of stirring distributes the mineral elements evenly, which makes the water feel especially soft on the skin. Also, yumomi serves as the perfect pre-bathing exercise, thereby enhancing the benefits of soaking in the hot spring tub. Nowadays, the water temperature is gradually lowered by channeling the hot spring water straight from the source into long wooden troughs.
Experience traditional culture
The yumomi ceremony involves two lines of women on either side of the bath chanting in time whilst churning the water with wooden planks roughly 180 centimeters long. This custom of cooling the piping hot water without diluting it and diminishing its therapeutic effects began sometime in the Meiji period. Today, you can watch a demonstration of yumomi and even try your hand at it yourself at the Netsunoyu bathhouse.
Scenes of yumomi can be seen at the 1:22 mark in the following video.