To XK and others with experience. How do you tell if a steel is
really Tamahagane. As a whim, I bought from Yahoo Japan Auction a
yanagi-ba (sashimi slicer). Its a vintage knife and the maker
stamped Tamahagane玉鋼 on the back side. Even before receiving it, I
suspect that for the price of 10,000 yen, its probably second grade
steel after the best was claimed by swordmakers.
On the stones, the edge doesn't feel as crisp as Hitachi white
#2 and I couldn't observe any folding marks. These lead me to the
following:
Does 'Tamahagane' refer to a method of steel production
regardless of quality and purity?
Is multiple folding a must for a steel to be called
Tamahagane?
Whoa...Deadstroke, this is a good question.
According to my friend, there are different grades of Tamahagane
(about 3-4). To my knowledge, Tamahagane is a category of steels
made from especially pure iron ore in powder form found in certain
parts of Japan. This natural powder ore is low in sulphur and
phosphorus content and other impurities that naturally make iron
very brittle.
To make the steel, the ore is further purified and treated using
a furnance, traditionally, a Tatara furnace is used. The steel
making process will take about 4-5 days straight and the workers
usually go without or little sleep. Of course, how long the process
takes exactly will depends on the orders of the master who can
judge when the steel is ready by the roar of the furnance fire,
color of the flames and by knocking on the furnace wall (will
produce a certain sound to indicate the steel is ready).
And this is the interesting part, the lumps of steel obtained
will be called Tamahagane. However, high-grade Tamahagane
used in the production of nihonto (Japanese-made swords)
will be silverish. Grey lumps are rejected as lesser-grades. The
Chinese have also learnt how to make Tamahagane from the
Japanese.
Now as for the manufacturing part and heat-treatment of
Tamahagane, this part is really up to the blacksmiths. They can
vary it as much as they like, they can choose to fold it or
not to, it all depends on their fancy. However, of course, certain
actions might weaken even the highest grade Tamahagane steels.
Hope you understand what I'm trying to say. In short, Tamahagane
is just a type of steel, with a few grades. How people choose to
use it differs from person to person.