One of the most enjoyable and distinctly Japanese experiences you can have is “taking onsen.” Onsen is a Japanese term for “hot springs.” Historically, onsen have been placed where there are natural hot springs from Japan’s volcanic activity. Over the years, it has come to mean any facility that offers hot baths. These facilities are often tourist attractions, and accompany resorts, hotels, and small inns.
Newer facilities design their own baths using the latest technology. They still tend to incorporate the outdoors as a major design element and inspiration. (Indoor facilities that are not heated geothermally are usually called sento.) The Japanese regard taking onsen as a leisure activity and a great place to bond with groups.
There are legal requirements to be called an onsen – the water must contain at least one of 19 designated chemical elements, and it must be 25 degrees Celsius or warmer before being reheated.
The cleanliness of the water and bacteria are concerns. Occasionally the additional chemical elements prevent bacterial growth, but proper upkeep and maintenance are necessary. Some resorts might also use chlorine in the water.
The baths or pools can be made from different materials, such as stone or wood, and the water in the various pools can have different qualities. The different chemical elements in the water can include radon, metabolic acid, sulfur, sodium chloride, hydrogen carbonate, and iron. These materials can give the water a milky or colored look. The Japanese believe that different waters in different locations have different healing powers.
Rules for Taking Onsen
First and foremost, it is considered bathing and will include showers, soap, and sinks. It is expected that visitors will wash and scrub themselves before partaking in hot soaks in the large pools.
While natural outdoor pools tend to be set in stone, tubs can be made from Japanese cypress, marble, or granite. Indoor pools can also be made with these materials, as well as tile, glass, and metal.
Japanese macaques (monkeys) have also been known to partake in onsen.