The origin of the public bathe(Sento)

The bath is one of the few practices which has not been imported from China, the origine comes from a purification ritual related to Shinto belief. Before entering in a temple believer have to purify themself with water. Taking a bath would therefore be associated with an other Shinto purification ritual; the salt heap in front of many houses or stores.
Before the development of the public bath, Shinto temples were the first places where ordinary japanese would take a bath.
There were two kind of bath:
* the "Yu" hot water bath and
* the "Furo" or steam bath.
Those bath were in a special building inside the temple court yard, not fare away from a wellspring. In the first room the water was heated in a huge wooden bath tub. The steam was conducted through bamboo tube in a second room, the "Yu-YU", with an other large wooden bath tube full of hot water.
The first Sento appeared during the Heian period (8th century).
Unlike temple bath where people was dressed in white yukata and silence prevailed, the public bath (Sento) autorized the nudity and talks. The name of such bath was "Machiyu" or literally "the hot water in the city"
During the Edo period with the developemnt of the cities the bath became a trully relaxation and pleasure place. The number of bath increased rapidely. Competition pushed the sentos to multiply services, like restauration room, relaxation room , massage and men who scrubbed ladies and ladies who scrubbed men. This evolution transformed the Sentos in the major socialisation place in the Japan. The development of mixed bathing has been helped by an all time tolerance of the japanese sociaty toward social nudity, particularly in the lower class.
This attitude was fondamentally different from the prudishness that prevailed in the West, where, since the middle age the nudity was comdemned by the Christian religion.
After the Meiji revolution with the opening of the country to the western influence, the japanese autorities imposed the gender separation in the public bath. Many of them built just a wall inside the bath room high enough to separe the view not the talks.
Similar evolution happened in the Onsen, but japanese people resisted to the western prudish pressure by using a small (or large ) bath towel to cover their body when soaking in mixed bath.
In most tradional onsen swimsuits are not autorized because it does not fit with the fit with the purification ritual of the origin