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The Sumihira Tatara A week in images at Manabe Sumihira's Zuku-oshi Tatara   The
furnace is fired early in the morning and for about 10-12 hrs. Each
load of pellet-shaped ore is added with a load of different sizes of
charcoal, allowing to control the speed at which the process advances, as well as
the more important reduction-carburization process. At some point, slag accumulates and can be seen through the windowed tuyères. It must be let out. Bits of liquified cast iron are trapped while flowing through the slag, and escape with it, burning instantly into beautiful fireworks.   In
preparation for the harvest, the crucible is pre-heated in a forge
(seen in the background on this picture) in order to dry it and
minimize thermal shocks.In order to pour the accumulated cast iron out into cake-sized molds, the top section of the furnace must be lifted away, and its base tilted to help the metal flow out into a crucible.  Mr.Manabe receives the liquid metal into the crucible, and rapidly pours it into the molds.   The furnace is taken appart and its bottom section emptied of remaining charcoal, metal and slag. This time only hachime (« honeycomb pattern ») cast iron was produced, a rather low carbon type (between 2 and 2.3%). In comparison, koorime (« ice pattern ») includes more, sometimes as high as 4%, and is clearly more fluid.  This cast iron must now be decarburized into steel. This is done about a month later.
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