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 UT), the water is beaten
with long wooden boards in order to cool it down to
SW, 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
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
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
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
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
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.