Ōgama Kilns
Ōgama (literally, “large kilns”) appeared in Mino in the late fifteenth century. These kilns, which were larger in scale than the anagama kilns, were only half buried, with their walls and domed roof remaining above ground. This allowed the firing chamber to be larger, and a door could be added to the side to make loading and unloading significantly easier.
By the time о̄gama kilns came into use, there had been other advancements in kiln technology. Instead of a single smoke-dividing pillar (bun’en-bashira), kilns had multiple small pillars that allowed for greater temperature control and therefore more success in firing. Stone paving inside the firing chamber gave it better heat retention, and a small retaining wall between the firebox and the firing chamber created a level surface on which to place the unfired pieces.
Another important technological change was the addition of stoppered peepholes, which allowed potters to check on the progress of the firing. In Mino, these holes were also used to extract items midway through the firing process. Potters would pull the red-hot pieces out and dunk them in water. This rapid cooling turned the glaze a deep black color called “Seto-guro.” By removing just some works midway through and firing the rest of the batch normally, potters could produce differently colored pieces in a single firing.