ROKUJURO

As we already stated in the TSUBA section and as Chris has pointed out above, construction, carbon migration and the potential hardness of steel depends of it's carbon content. Heating steel to a temperature above 900°C in an oxidizing atmosphere leads to a loss of carbon on it's surface. At the same temperature carbon will start to migrate within the steel package to layers with less carbon content. As we said, time of exposure, temperature, and thickness of layers are the facts to count with. (In a specially created, highly carbon saturated atmosphere steel can as well increase it's carbon content which was a method of old times to make steel from soft malleable iron). In KATANA the carbon content in the cutting edge is often found to be about 0.7 to 0.8 % while other sources mention as much as 1% C. Theoretically, a sandwich-construction with high-quality KAWAGANE (refined with up to 15 foldings/weldings) and a SHINGANE core (with about 10 foldings) has the same properties as a mono-material of the same KAWAGANE quality. The core in such a construction is - theoretically - 'passive' when the blade is being used in slashing while the KAWAGANE skin is 'active' and has to withstand all material stress. But it is evident that this depends on the internal quality of the blade, eg. even layers on both sides and no flaws. In practice the mono-material is suitable for long blades if it is perfectly homogenous with no voids or uneven carbon dispersion, and if it is differentially hardened with a hard edge (with about 60 HRC found on many blades) and a soft back (roughly 50 HRC) The sandwich construction requires the same meticulous process and hard work with the advance of less high-quality material being needed in the KAWAGANE. Nevertheless the 'marriage' of core steel and skin steel was always critical (depending on the construction of the blade) as it was easy to close in small particles of carbon or to produce tiny gaps in places where the welding was imperfect, causing FUKURE at later stages of polishing. The quality of both constructions would depend on a perfect hardening process. If we compare these Japanese techniques with those in early Europe we find fire-welded blades in Celtic swords of 500 B.C. as a necessary process to homogenize the steel. We do not know if these blades were etched or specially polished as to produce a Damascus pattern but the early Vikings (500 to 1000 AD) started their sword forging with a Damascus-type of steel. Later after 800 AD the Francs succeeded in making very good mono-material steel being as good as Damascus but proved to be less work. This made the Vikings import large amounts of sword blades from the Francs. Going back to Japan we hear about many inferior blades in times of war which were mass-produced under unfavorable conditions or by less qualified smiths. Even today many swords with KIZU are on the market which would not have withstood a severe blow (HAGIRE!). In the same time we have very good swords being preserved to our days, and these were often made by renowned KAJI. In this context we must not forget that many SHINTO and later swords were never tested or used in combat. It is evident that long blades made for slashing are very demanding in construction, but both types of construction - mono-material and composite/sandwich - could be made to the requirements of those days' warfare if the material was good enough and the skills of the smith as well.

You can find black waterbuffalo horn at most of the knifemakers' supply shops. Regards, Jean C.

I would like to underline this. I already wrote about this subject on Saturday: (......One word to the subject of carbon diffusion. This is influenced greatly by time, temperature and the way to travel , e.g. the thickness of layers. It ist quite well possible to create a decorative Damascus steel from high carbon steel and carbon free iron without having considerable carbon diffusion. This needs as few weldings as possible and thick layers. When it comes to longer periods of forge welding and folding, the overall time of heat application gets longer and the layer diameter diminishes, ending in a balanced carbon content in all layers. An obstacle to carbon diffusion is a layer of pure nickel.....). Steel 'behaves' like steel, and the knowledge of general physical properties of steel is helpful in understanding forging techniques of TSUBA.

Andy, Critics on the content of a treatment are not an attack on the writer! If I correctly understand these forums, most NMB members are interested to improve their knowledge, and critical opinions and discussions may well serve this purpose. I am sure you wrote the text on TEKKOTSU in the best of your knowledge, but as so often opinions are just individual thoughts and not facts. My critics are based upon my personal experience and knowledge, and I am willing to learn if you could prove my comments to be wrong. But then some fat books have to be re-written at least in parts.... Kindly check my comments, you will find that we both are striving for the same 'truth' behind some very special forging secrets. Regards, Jean C.

A very good day, gentlemen! As an active knife and traditional tool smith I have some experience with steel and it's properties. Japanese arms present some of the most advanced forging techniques we can find in steel, and this fact brought me to the subject some forty years ago. Nevertheless I still feel like a beginner because of the vast field Japaneses arts and crafts represent. Although other cultures also developped high skills in this field, I am especially fascinated by traditional Japanese forging. Quite a while ago I found the NMB forums and I was delighted to find so many important informations and highly knowledgeable members. I hope I can contribute with my experience from time to time, but I will be here mostly to study and learn, especially in the field of TSUBA. Best regards, Jean Collin

Dear NMB members, may I use this fascinating thread to present myself as new on board? I am greeting all members! Still learning, I am in contact with Japaneses arms since nearly forty years. As an active knife and traditional tool smith I have some experience with steel. A few years ago I began to research about TEKKOTSU, discussing the theories with other TSUBA collectors. Some were in opposition to my own knowledge and practice with the properties and the 'behavior' of steel. I have been reading quite a while here in the forums and as the discussion in this thread turned to TEKKOTSU I thought it might be helpful to add my personal observations and ideas to this subject. To start with, I want to say that I fully agree with what Ford Hallam said about it. As long as no scientifical examination has been made, one has to accept what is known about steel, and belief or even conviction are not helpful. Let me start with the article from Andy M. where I found this contradiction (among others which have already been cited). I cite:.....Tekkotsu may be defined as segregated areas of high carbon content, formed as a result of a process of successive episodes of heating, folding and hammering of an iron plate. Generally speaking, increasing the carbon content in iron results in decreased ductility...... The last phrase is correct, but then the less ductile hard steel in a TSUBA would not protrude between layers of softer iron as to form TEKKOTSU. Working on the anvil, steel and iron can be well differentiated even at higher forging temperatures. Steel would not be 'squeezed' out between layers of iron. Imagine a steak instead of a hamburger in a BigMac..... Most of the members here have probably seen TSUBA with sword cuts on them. These are fine, sharp edged grooves. Try to do that with a hardened TSUBA! On the other hand I have yet to see TSUBA with chips that could lead to the conclusion that a blade hit a hardened metal obstacle. The description of 'dense, hard steel' is misleading. You cannot densify steel by hammering or any other technique, the density is always 7,85 (roughly). Of course you can hammer down a piece of TAMAHAGANE and densify it's structure, eliminating any voids that occurred in the process of production. But there is no such thing as 'dense iron'. The surface of a TSUBA may well give an impression of more or less structure, but this has nothing to do with the metal's physical properties. It was mentioned that acid treatment might eat away some superficial parts of the material and thus leave TEKKOTSU on the surface. I believe that this is correct, and if so, it supports Ford's theory that TEKKOTSU is more likely iron (or low carbon content steel) because the acid works best on high carbon steel. If on the other hand TEKKOTSU was indeed high carbon steel, we would find hollowed out grooves and lines in TSUBA MIMI instead of TEKKOTSU standing out. Relating to the etching processes I may add that all metals used in TSUBA were chemically treated or patinated with the exception of gold. In some places, silver was also left untouched. I do not mean that all TSUBA were treated, but these patinations were not only applied for aesthetic purposes but as well for corrosion protection. As examples, the well known SABIJI on iron or the 'foxes' red' on copper are very durable coatings, and not all recipes are yet known, as far as I know. In an attempt to prove my ideas to myself I made some samples with different layers of iron and steel. After forge welding them I ground them smooth at the sides and hammered them down at usual forging temperatures. The results were as expected: it was the softer iron that came visibly out at the sides. Going back to the production of steel one hast to remember that rather impure TAMAHAGANE had (and still has) to be processed with repeated folding and welding to become a refined and usable sheet material. It has nothing to do with intended production of layered steel material for improved impact stopping capacities as mentioned in the article. The fact that the production process is sometimes still visible in the workpiece has - at least in my understanding - more likely to do with a typical Japanese attitude found in many artistic and crafts fields such as metalwork, SUMI-E, pottery, and some woodwork. One word to the subject of carbon diffusion. This is influenced greatly by time, temperature and the way to travel , e.g. the thickness of layers. It ist quite well possible to create a decorative Damascus steel from high carbon steel and carbon free iron without having considerable carbon diffusion. This needs as few weldings as possible and thick layers. When it comes to longer periods of forge welding and folding, the overall time of heat application gets longer and the layer diameter diminishes, ending in a balanced carbon content in all layers. An obstacle to carbon diffusion is a layer of pure nickel. To increase research on the forming of TEKKOTSU we could also ask those TSUBASHI who are still able to produce TEKKOTSU, as I heard. But I am afraid there will be no satisfying reply for Westerners, when the artists answers: I use the same material as my ancestors and the techniques my master taught me, and the results are as expected..... Regards, Jean