A donabe survives an open flame because the clay is full of gaps. Marubashira is a valley settlement where the kilns are gathered: workshops making Iga-yaki casseroles and heat-resistant vessels, a hall for the local industry, and a climbing kiln. The clay here was laid down on the floor of an ancient lake, and it carries fragments of plant matter that burn away in the firing, leaving a fine porosity behind in the body of the pot.

Those gaps absorb sudden changes in temperature, so the ware can go straight onto a flame without cracking, and Marubashira became a district that makes cooking pots. The city of Iga is about thirty minutes away by car. Notices seeking successors are posted at the kilns, so for a settlement in a valley of this size there is more movement of people in and out than one might expect. The climbing kiln is a row of chambers set along the slope; the fire is lit at the bottom and drawn upward through each chamber in turn, which is why it needed a hillside to work at all.

The character of a producing district is usually decided by what is underfoot. Marubashira did not choose to make casseroles and then look for suitable clay. The clay was here, and the least strained thing to do with it was to make vessels that could take direct heat — the order of events runs the other way round from the way such stories are usually told. The kilns cluster in this valley for the same reason: there was never a good argument for moving away from the deposit, and a workshop that leaves the clay behind has given up the only advantage it had over every other workshop in the country.