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of the metal.
    Now this certainly isn't a book on metallurgy, but understanding the basic material that is used to make a sword, and its properties, is important to understanding the weapon, and how it was, and was not, used.
    Carbon is the principal alloying element in the manufacture of knives and swords. Although other elements can be added, and will produce some minor changes, it is carbon that makes the most difference. Today we can add chromium and produce stainless steel, add various other trace elements like molybdenum and vanadium, and produce tougher, stronger and better blades. Some of these trace elements were in the various legendary ores, and they produced swords that were better (forging and tempering being equal) than other blades made from bog iron ore or ore with none of the valuable trace elements.
    Iron that contains .05 percent to .20 percent carbon is considered low carbon steel, and is little better than iron. At best it can be called a "steely iron." Although better than bronze, it does not make a good sword. Medium carbon steels, containing up to .70 percent, make a good blade. It can be tempered and, although it will not harden to the same degree as high carbon steel, it will harden and take an edge. The best swords are made from high carbon steel, with a carbon range of up to 1.00 percent. Any higher than this and the carbon shows a strong tendency to make the blade entirely too hard, and subject to easy breakage. (Understand that these figures apply to swords made prior to the 20th century. Modern alloys can make very good sword blades without the same amount of carbon.)
    But carbon content alone does not make a good sword. Heat treating, or tempering, is the most important factor. You can have a sword with a medium carbon blade, and one with a high carbon blade, but if the one with the high carbon blade is not tempered properly, it will be inferior to the other. The tempering process was another area that allowed for "secrets." Water is an excellent cooling medium, but it has one problem. Unless the water is highly agitated, it will immediately steam and create a barrier that will delay the cooling process, thus you get uneven cooling. This is particularly true for a large object like a sword. This is why running water was used, and why a fall of water was preferred. But fresh water isn't the only medium; brine is very good, as well as oil. All of these make good tempering mediums.
    One quenching medium that was not used was a slave, into whom the red hot sword was supposedly thrust to gain some occult property. This is one of the more popular and ridiculous myths that permeate this field. Aside from the moral considerations that our ancestors did, and did not, have, it simply wouldn't work anyway. The human body simply could not remove heat quickly enough to make an effective tempering medium. Nor could it be done in a uniform manner. It sounds good and romantic and magical, but it simply isn't true.
THE FORGING PROCESS
    The forging process was usually started with a "cake" of steel. This was a piece of steel about two pounds in weight and was usually obtained through trade. A swordmaker was lucky if he lived close enough to a good source of metal. But this usually wasn't the case.
    The steel was heated to a cherry red and then pounded into a bar. This process was repeated several times, and eventually it was shaped into the sword blade. The Japanese had a process whereby they would take the carbon containing iron and fold it over many times. This allowed the carbon to disperse throughout the sword, making a blade that was generally homogeneous. This folding ensured that any welding flaw did not go fully through the blade, thus helping to keep the blade from breaking under stress.
     
    Cross-section view of a Japanese sword.
     
    The Japanese also used several other techniques designed to produce a superior blade. They would enclose a high carbon center with a mild steel skin, allowing the edge to