Potter's wheels and other technologies were introduced from the Asian Continent to Japan about 2,200 years ago, in the Sueki period. Potters were able to make their ware much more quickly, and the shapes were more regular than Jomon ware. Sueki was still low-fired ware.
Until the Momoyama Period, about 1580-1600, most Bizen potters were farmers in summer, and only made their ware in wintertime when they could not work their fields. They built large communal kilns, and cooperated to load and fire them.
Because they only made pottery intermittently, they "got rusty", and some of the pots they made are not perfectly regular in shape. Despite the flaws, though, I find the simplicity of many of these pots very appealing. One of my great challenges as an artist is to emulate that "yep, it ain't round, but it holds water" style, and at the same time to make that simplicity appeal to people, so that you will be happy to buy my pottery!
Bizen Pottery in the Edo Period, 1600-1868, was technically quite well made, but its style was rigid. The Ikeda Clan, which controlled the Bizen area, had underwritten a pottery guild comprised of six families in Bizen. They were granted special permission to gather firewood without rendering some of it as a tax to the Ikeda Army. Instead, they made large urns for catching rainwater, and other items of use to the Ikeda Clan.
In the early 1600's, the Kimura Family was commissioned by the Ikeda Clan to make Bizen tiles for the roof of Shizutani Gakko, one of the first "public" schools in history. The Shizutani Gakko Campus is still open to the public, and I encourage people who like Bizen Pottery to visit the school and see the tiles.