What is Yumomi?

Here at Kusatsu Hot Spring there is a long-established system of hot spring cure known as Jikan-yu (timed bathing) - a system famous for its austerity. As the original spring is extremely hot (around ６５℃), the water is beaten with long wooden boards in order to cool it down to ４８℃, a temperature where bathing is possible. Often, even when the top layer of water cools, patches of heat remain underneath, but by beating the water, this phenomenon is prevented. The process is called yumomi, and it is only safe to commence bathing after yumomi has taken place.

This action is necessary to cool the water down and is an essential preparation for bathing in high temperatures. It also has the therapeutic effect of helping with the aspiration of steam.

Is it really possible to bathe at temperatures of 48℃?
48℃ is much too hot for bathing with regular water. But it is possible to bathe in densely concentrated spring water like at Kusatsu Hot Spring (which contains highly acidic hydrogen sulfate alums and copperas). The reason for this is that yu no hana from Kusatsu receive direct sunlight and crystallize when coming into contact with the air.

Through the yumomi process, the hot spring water and air are brought into even greater contact, causing more yu no hana to be created and thereby a further increase in concentration density. As the yu no hana are colloidal, they form a thin coating around the bather's body - the effect being that he/she feels the temperature to be lower than it really is. In Japanese, we say that the water has become softer, gentler, almost buffeted - this is not the same thing as the temperature simply being lowered.

Also, when we perform yumomi, we sing the traditional Kusatsu song and the Kusatsu yumomi song. The act of singing causes us to breathe abdominally and has a beneficial effect on the treatment. (For more information, please refer to the section on Good Breathing Tips/Taking a Timed Bath)

Since 1960, a tourist yumomi show has been performed at the Netsu-no-yu entertainment hall. This is aimed solely at tourists and is not genuine yumomi.

Genuine yumomi can only be experienced by taking part in jikan-yu (timed bathing). Yumomi has a medicinal purpose and therefore a certain brave, almost heroic determination is required to take part. It's certainly not something to go into lightly!

In the Edo period, people apparently bathed in springs of temperatures of up to 55℃, but this was certainly much too hot for safety! Nowadays we bathe at temperatures of 48℃).

For your reference, the temperature of the water we use depends on the ailment we want to cure, and can vary between 44 and 48 degrees).


Note:Jikan-yu is now available at Chiyo-no-yu (since 2002). This is a serious medical treatment, so please think seriously before making your application.

Note: Jikan-yu has also become available at Jizo-no-yu. Again, it's only for serious bathers - please telephone 0279-88-2072 for more information.