The most common Japanese bathtub is called a furo or an ofuro. The first ofuro were made out of wood, but modern baths are created from acrylic glass, tile, or stainless steel. The ofuro inspired the Western bathtub, but the two bathtubs have a couple visual differences. An ofuro is smaller, deeper, and has square, boxy sides. In contrast, a Western bathtub is longer, shallower, and has sloping sides.
In the past, ofuro were heated by a wood burning stove underneath the tub. Nowadays, the modern bathtub has a recirculation system that filters and reheats the water. Some families use the hot water from the finished bath to do their laundry in the washing machine. Japanese hot tubs (http://www.mybath.biz/servlet/the-Hot-Tubs/Categories) or spas are extremely warm, and are commonly heated to a temperature of 100-108 degrees Fahrenheit.
In traditional bathing, the entire family uses the same bathwater. The oldest male or the guest of the house goes first and the rest of the family follows in order of seniority. However, many young women in modern times refuse to bathe after their fathers. In families with larger tubs, it is not uncommon for families to bathe together in the same tub. Many parents bring babies and toddlers to the bath with them.
Ofuro are meant more for relaxing than they are for becoming clean. Because the entire family uses the same bathwater, it is considered extremely rude to go into the bath without becoming completely clean beforehand. The bathroom fixtures (http://www.mybath.biz/) usually include a small faucet or shower along with the ofuro. The bather sits on a small stool where they scrub their skin and wash their hair before entering the bath. Many bathrooms are much smaller than Western bathrooms set up in a similar way to walk-in showers.
While several modern homes and hotels have private bathtubs, many people still use public bath houses or sentō instead of private baths. Males and females are almost always segregated, excluding the extremely rural areas of Japan. Almost all baths do not allow swimsuits or towels to be worn in the bath, everyone is completely naked.
Sometimes bathers use a small hand towel to cover their genitals as they move out of the water. Many hotels offer these hot baths to their customers. Sometimes they are outdoors or on the roof. It is especially crucial to be completely washed and rinsed before entering a public bath. Bathers who contaminate the communal bathwater with outside filth are considered to be extraordinarily rude.
Onsen are baths and bath houses that use water from natural hot springs. They are usually located around the hot springs in question, and many of them are outdoors. Outdoor baths can be made out of granite, Japanese cypress, or marble.
Though the dry sauna and the regular sauna (http://blog.mybath.biz/the_my_bath_blog/2008/11/7-benefits-of-c.html) is of Finnish origin, saunas can be found in many Japanese sports centers and public bath houses. Like the baths themselves, these saunas are separated by gender and nudity is required.
Bath houses in Japan used to be extremely common, especially after World War II. However, there are less bath houses in modern times because of fewer customers. More and more people are able to afford houses that already have bathtubs, so they do not feel as inclined to use the public bath.