Jun works on batches of 6 to 10 at a time because once the bases are fashioned they must dry for several weeks before they're strong enough to support a 400-pound superstructure. He also makes relatively large batches because out of a group of ten only 2 or 3 will survive the dangers of the coming months. Even flipping the base is a challenge. As the walls build higher, the dangers mount. The clay can't be too thick or too thin, too wet or too dry, too soft or too hard.
Timing is crucial.
The lower levels have to be dry enough to support the increasing weight but supple enough to merge with the fresh clay. Actually everybody doing clay work makes dungo 'cause dungo in Japanese is a dumpling. Then when you start using clay usually people end up with a bowl shape. Everybody is doing it, but I guess I got idea from that part of it. Usually he won't even try and if you try to explain it, he probably won't agree.