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Tsumi wakashi (stacked and heated) again

After finishing Shita-gitae with three types of steel, Tamahagane (literally "jeweled steel"), Sentetsu (pig iron), and Hocho tetsu (literally "kitchen knife steel," pure iron), they are hammered using a Kozuchi (light hammer) again to make metal pieces, selected to produce the proper steel composition, they are stacked and formed like the first Tsumi wakashi. In this step, four kinds of steel having different carbon content, Shingane (center metal), Munegane (back metal), Hanokane (blade metal) and Gawagane (side metal), are made.