On the weekend of March 26-27, 2022, I met up with my friends Bitner and Loki and the guys from "Nože Z Vostra" at our place in Pálovice to test the new kiln for tamahagane production. For the reduction we used iron sand, a magnetite of extremely high chemical purity, as the raw material. We smelted in two furnaces. The first, already tested several times in the past, is made of refractory steel with a fireclay lining with an inner circular diameter of about 40 cm. The air is blown in by one pump. Insertion of approx. 30 kg of satetsu and 110 kg of charcoal. Reduction time approx. 3 hours without preheating the furnace. The kiln was operated by Bitner. Two melts were carried out. Result of kera approx. 13 kg in the first melt, two compact kera weighing approx. 12 kg in the second melt. In the second smelting, the charge was a combination of satetsu and partially reduced ore from the previous smelting in a large tare. This is essentially magnetite reduced to hematite, which was crushed into small segments of 3 - 1 mm. This material is easier to reduce. This was very noticeable when the slag was repeatedly tapped, which was completely liquid and flowed out of the tapping hole at the bottom of the tatara in a strong stream. When pure magnetite was used, the slag was much denser and flowed out lazily and in smaller quantities.
The second furnace was brick, with a square base and a wall length of about 60 cm. In the first smelting the air was drawn in by two pumps, in the second smelting by one pump. The charge was about 40 kg of satetsu and 150 kg of charcoal. Reduction time approx. 4 hours. The furnace was operated by Loki. The first smelting resulted in 4 kera, one high carbon, almost cast iron and three smaller compact kera of high quality high carbon tamahagane weighing 3-5 kg each. The second one-pot smelting was carried out very carefully with minor changes based on the results and experience of the first, test smelting. The result was a huge kera of about 20kg and one smaller compact kera of about 3kg. The large bark is compact, consisting of high carbon steel. There is a smaller protrusion at the top which has not been fully reduced by the ferrous sand. This part of the kera shows the process of reduction, the conversion of iron oxide into steel.
In the second charge, the steel was reduced to almost 70% of the weight of the satin used. I consider a 30% reduction to be successful and usually the results are around 40-50% reduction due to the extremely high quality of the ore.
Thanks to smelters Bitner and Loki and the boys from "Nože Z Vostra" for their assistance and help. This time I enjoyed the positions of observer, picker, tonger and advisor and I only operated the grill. Special thanks also to Pavel Holub, who recorded the event and will produce a documentary on it. And of course thanks to Zuzana for her service, background and tolerance of the excesses of the boys playing. And to the assistants dogs Morgana and Shen.
