When I hear the words "cast iron," I typically think about frying pans, and how I know I'm supposed to season them but never quite do it right. I've certainly never thought about the process involved with creating cast iron, and what exactly makes it unique or different—but now I'm intrigued!
Earlier this week, musical marketplace Reverb released a pair of new limited edition guitar pedals in collaboration with Earthquaker Devices and KGR Harmony featuring cast iron cases built by Oitomi Ironworks, a Japanese forgery. As the KGR website explains:
KGR HARMONY effects pedals are housed in cast iron enclosures made using a centuries-old technique known as Nanbu-tekki (南部鉄器). They are cast by handat Oitomi Ironworks in Ōshū City, a forge that has operated since 1848.
Traditionally used to make items as varied as teapots and hand guards for swords, Keijiro Fukushima has combined the technique with innovative circuit design, guided by a finely-tuned ear for inpsiring, musical tone. KGR HARMONY's effects are unique; modern, yet deeply rooted in tradition.
As I learned, Nanbu-tekki is a traditional Japanese iron casting method known for its intricate designs, and for being lightweight and occasionally musically harmonious. Oitomi in particular is a family-owned company that's been around for over eight generations.
While the video above admittedly focuses more on the pedals than the process, I was intrigued by the glimpses I saw—particularly the way the Oitomi ironsmiths literally cast the iron blocks into what appear to be piles of sand or perhaps iron filings, essentially washing the metal to give it that unique texture. (You can see it for yourself around 0:46.)
I was intrigued that I had to look up more, particularly this from Kogei Japonica:
A mold is made by mixing sand and clay using a wooden pattern. This method is called the "baked mold method," and by drying and baking the mold, the shape of the product can be firmly maintained. The mold is created by rotating the wooden pattern by hand, forming the shape of the product.
Next is the work of pressing patterns that will emerge on iron kettles and teapots onto the surface of the mold. Patterns of Nambu Tekki include the "Arare pattern" and animal/plant patterns.
[…]
Finally, the mold on which the pattern and surface treatment work have been completed is completely dried and baked with charcoal fire at about 1300 degrees Celsius. By baking, the mold gains strength and can withstand casting.
So it is literally a mold made out of sand! Amazing! And then what?
Next, the molten iron is taken with a ladle-like tool and poured into the mold. At this time, the thickness of the iron kettle is determined by the gaps in the mold and the core. As gas is generated inside the mold due to the high temperature, ingenuity such as securing gas escape routes is necessary.
After pouring, weights are placed on top of the mold to prevent floating. This series of operations is called "fuki," and it's the moment when the artisan's skills shine the most.
Afterwards, the mold with the poured iron is cooled, and when the product has solidified, a process called "demolding" is performed to remove the mold, but the product is still rough at this stage. Therefore, the core of the product is also removed at this stage, and work is also done to remove burrs formed at the seams of the mold.
I am fascinated.
Previously:
• Is antique cast iron cookware really better than new?
• Clearing up some myths about cast iron cookery
• How to restore cast-iron waffle irons for fun (and waffles)
