Creating a Cast Iron Tetsubin Kettle
Sand is scraped into the desired shape to create a mold. (photo: Kunzan Workshop) |
The process begins at the design stage. A sketch is made which is then transferred to a sheet of metal 1.5mm thick. This forms the template for the mold. Different textures of sand and fine soil are used to create the mold using a special scraping tool. |
The inside of a fired mold showing a recessed design. (photo: Kunzan Workshop) |
Various tools are used and designs vary from “Arare” (raised bumps at regular intervals)
to incredibly detailed scenes of flowers and animals, some drawn using a transfer sheet and others completely freehand. The imprinting of a design has to be done while the sand is still damp. Working quickly to produce a balanced finish takes years of experience and a steady hand. The mold is fired at 1300°C (704°F) after being decorated. |
Individual molds for lid knobs. (photo: Kunzan Workshop) |
Molds are also made for the lid knobs. Even pieces as small as these are crafted with precision. Thin lines of sand are placed on the inside of the molds to achieve the desired effect. |
A moment of intense heat and concentration when the kettle is born! (photo: Iwachu Cast Iron Works) |
The outer mold consists of two halves. An inner mold (made of sand and clay) is sandwiched between the two,
leaving a thin space into which the metal is poured — this thin space becomes the kettle’s body. Metal is melted in a furnace to a temperature of about 1400–1500°C (760–815°F). The molds are placed on an ash pit and held stable with long wooden slats. The molten iron is poured carefully into the molds, emitting sparks and small bursts of flame. |
Video: The casting process of Nambu-tekki kettles (Iwachu Cast Iron Works)
Kettles stacked after the oxidisation process. (photo: Kunzan Workshop) |
Once the metal has hardened, the molds are removed and the kettles are cleaned.
Each mold has to be repaired after almost every use and can only be used about 3–5 times (1–2 times for delicate designs).
Broken molds are not discarded but reprocessed for reuse. Charcoal is heated to a temperature of 800°C (426°F) and the kettles are steam-baked for 30–40 minutes, resulting in an oxidized coating that helps protect against rust. |
Finishing touches by an experienced craftsman. (photo: Kozan Workshop) |
A pot is heated to 250°C and urushi lacquer is applied with a straw brush, giving the kettle a glossy sheen. Afterwards, iron stain (ferric tannate) is applied to achieve the matte finish. |
Hammering sounds echo around the workshop. (photo: Tanaka Tsuru Blacksmith) |
The kettles are completed with the application of a handle made at a special workshop. The most difficult handles to make are hollow — created by pounding and curling iron sheets inward. These handles are prized as they are light and stay cooler than solid ones, typically used on higher-end models (approx. over US$700). |
Today’s workshops continually strive to create pieces relevant to modern lifestyles while staying true to traditional roots. This introduction was compiled based on visits to workshops in the Morioka area; some processes may vary slightly between craftsmen.