How a Katana is made

In my last post, I told you about the Katana and how incredibly awesome it is. Here, or in a few other posts, as it is a long process, I will tell you how it is made.

At the Blade-smith’s shop, the pieces of special steel, called Tamahagane, arrive from the smelter. There are two types of steel, one with high carbon content, which makes is hard but brittle, and low carbon content, is tough but not very hard. Both types are needed for the sword.

The smith hammers together the pieces of hard steel together (he can tell which type is which by the color: the hard steel is much brighter than the soft steel), folding it over and over, each time doubling the layers of steel, and finally hammering it out into a long, wide bar. He then hammers this into a U shape. Then, he forms the soft steel into a bar about half the width he hammered the hard steel into before he folded it, and inserts the soft steel into the hard steel, whacking them together.

What is interesting is that so far, the smith has not formed the blade into a curve: it is still straight! Now the smith begins forming the edge of the blade, it is not sharp when he is done, of course, the actual sharpening will be done with sharpening stones.

Now for the heat treating. The smith paints a sort of paste over all of the blade except for the edge, you will see why they do this. The smith darkens the room: this helps so he can see the color of the heated metal, and the heating begins. The forge is heated, with the apprentices pumping at the billows (yes, the apprentices get to do all the hammering too), and the blade is placed among the glowing coals. The smith stays nearby, ready to take the blade out as soon as it reaches a dull, cherry red color. Once it reaches this color, the blade is removed from the furnace and plunged into a bath of cold water. Two things happen when this is done.

One is that the blade curves itself. This is because low carbon steel, when heated, expands, and when it is cooled, shrinks. The high carbon steel does not do this, so when the blade is cooled, the back of the blade shrinks, pulling the blade into a curve.

The second thing that happens when it is cooled is that when the steel is heated, the atoms inside rearrange their pattern in which they are set, and when the blade is so quickly cooled, they do not have time to go back in their original places, and so the edge turns out very hard but also brittle. However, the paste keeps the parts of the blade it touches from cooling too quickly, and so the back part remains tough.

The blade is sent to the sharpener, who sharpens it to the sharpness of a razor and polishes it, showing a wave where the heat-treated and non heat-treated parts meet.

Finally, the blade is fitted with a handle, and the finished sword is sent back to the smith, who can now view the beautiful result of his work.


One thought on “How a Katana is made

  1. Pingback: A Discovery! | Caleb's Gems and Minerals

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