Posted on 2011.11.21 Mon 16：50：28 edit
Before I start to create a blade, as a preparation, I made "Oroshingane" steel today.
I learnt about how to make Oroshigane steel from my teacher, Kunihira KAWACHI who is a Mukansa swrodmith and also an intangible cultural treasure of Nara prefecture when I was his apprentice.
I have 2 ways to make Oroshigane steel.
The first one is that I heat and melt pieces of pig iron, so called “Zuku”, in “Hodo” and the second one is that I did it in a small furnace like today.
Except that Hodo should be almost repaired sometime soon, I rather use the furnace since I don't want to damage Hodo.
I take one out of these 2 different ways considering the condition of Hodo.
This time, Hodo is still useful so I decided to take the latter way. (Oroshigane making in the furnace).
I guess most of people are wondering why I make Oroshigane steel such as a recycle of pig iron or steel in spite that I’ve already had enough Tamahagane for swordmaking.
In my case, by blending Oroshigane steel with Tamahagane in forging process, the combined steel becomes stickier. I express it “Sticky”, but sorry I can’t find the exact word in English.
But I would like to mention that Oroshigane steel is like a hidden flavor. Of course it should be fine to forge only Tamahagane and create a blade. By forging them together, I would be able to create an original sword with more interesting and beautiful Jigane.
These nails are from old shrines and temples.
Since almost 20 years ago, I've asked "Miyadaiku" (the traditional carpenters who have professional skills to build/repair a shrine and a temple) to provide me old iron made by Tatara method when they renovate or rebuild shrines and temples.
Note that the nails made by Tatara method are used for temples and shrines in Japan.
All the nails were made before the early Meiji period so oldest ones must be made long long time ago you could guess.
If I put too many nails themselves into the furnace, nails are not melted finely so I cut them in proper length, about 1.5 cm each.(Refer to the photo I posted below.)
As you know, the amount of carbon contained in the nails made from pig iron(Zuku) is low. Thus I have to adjust the amount of carbon to create Oroshigane steel containing higher amount of carbon.
First of all, I pick up some nails and pieces of Tamahanage and put them into the furnace.
Carbon from the charcoal combines with them in the furnace heated up to about 1,500 degress.
After finishing the first Oroshigane making, I confirm how much or what kind of iron I should use looking at the surface color and the weight of finished Oroghigane steel.
From the second time, I used only old nails for 2kg.
It takes about 20 minutes to make a mass of Oroghigane steel.
It is time to stop when charcoals around the steel are burned completely and the tuyere appears.
In the furnace, I hear Oroshigane steel breathing like a creature.
Opening the small door of the furnace and taking out charcoals, Oroshigane steel appears in front of me.
As soon as I pick it up with Tama-Bashi, I plunge it into cold water.
And finally Oroshigane steel was created.
Their color and surface are perfectly good and also shapes are nice as you look at them.
I repeated this process 10 times today and created 10 masses of Oroshigane steel.
As I told you above, Carbon is combined with iron in the furnace but in addition to that, at the same time the amount of phosphorus is reduced. Therefore completed Oroshigane has flexibility with both hardness and stickiness.
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