The making of the katana blade
The most important part of a saber is obviously its blade, clothing (KOSHIRAE), often sumptuously decorated, is only considered in the second phase. The value of a katana (market value, but also its artistic value and especially its importance as a weapon) is the quality of the structure that makes up its blade but also the condition of this same blade.
The 3 stages
The manufacture of this blade is carried out in three equally important stages: Forging, Dipping and Polishing Whatever the school and the master blacksmiths of the time, the manufacturing principles remain immutably identical:
Mixture of iron and steel.
Folding of these two components on themselves several times.
Dipping in water, the edge is soaked harder than the rest of the blade.
Very refined polishing in the final since it highlights the steel designs (JI HADA) due to forging, and the quenching line (YAKIBA)
Each forge school jealously guards its manufacturing processes. These are passed on by word of mouth, from teacher to student. This information most often relates to the number of times the steel has to be folded back on itself and the temperature of the water used to quench the blade.
The katana blades are made of two parts: the central iron part (SHINTESTU) surrounded by the second part, a steel sheet called UAGANE. The complex metallic amalgam of this structure makes it possible to obtain formidable weapons, rarely equaled. The unique quality of the Japanese blades is that they have a very high hardness on the cutting edge and an elasticity of the whole so that they do not break in combat.
The forging of a blade begins with the manufacture of the UAGANE. the master welds an iron bar to a steel plate of about 13 x 8 cm, called DAIKANE. On this steel plate, the blacksmith deposits pieces of crude foundry iron, a little clay and charcoal dust: it is TAHAMAGANE. He then pours water and limestone dust (UCHIKO) over the whole.
By this operation, the blacksmith adds carbon to the metal and limits the risks of oxidation which would interfere with the good welding of the different layers of metal between them (the charcoal is quantitatively dosed according to the flexibility required for the blade).
This amalgam of metal is red hot on a charcoal fire (HODO), then flattened with heavy hammers. As the temperature drops, the blacksmith sprinkles the metal with a mixture of water and ash and plunges it back into the brazier. When this piece is stretched, the blacksmith folds it back on itself, pours very liquid clay mud on it and heats the whole before a new hammering. This process is carried out about twenty times. The result is in the form of a steel plate made up of many thin layers and extremely welded together.
The very careful forging of the metal ensures an important quality. The homogeneous compression of the metal (non-existent air bubbles) gives it high resistance, more lightness and therefore more maneuverability.
Second phase of production: the SHINTETSU (iron core). It is a procedure almost identical to the first, except that less carbon is added to TAHAMAGANE and the number of folds less consequent (a dozen) The number of folds is not left to chance, and acts on the final quality of the blade. It appears that after twenty-one folds, the metal loses in hardness and this significantly.
The third, and quite obvious operation, is the unification of the two products thus obtained (UAGANE and SHINTETSU). You have to fold the UAGANE all around the SHINTETSU by welding them together.
The amalgam thus produced is then heated and hammered in order to obtain a shape quite close to the desired blade. This bar is eroded using a two-handle file (SEN), to obtain the final shape of the blade.
The blade thus formed is tempered in order to harden it and make it an effective weapon. The sharp part of the blade is hardened harder than the rest. This procedure gives a very strong and relatively soft edge so as not to break. The quenching is called YAKI IRE. The quality of the blade is largely defined by this process.
All the work of the blacksmith is called into question during this operation. The red-hot blade comes in contact with the water, there is no room for error. A defect in soaking reduces the blade to a common bar of steel. Some blades have been taken in soaking, but they do not have the class of others.
The blade must be prepared before the actual quenching, in fact the blacksmith coats the blade in a layer of refractory clay.
When this envelope is dry, the blacksmith removes a part of it by making a simple woody shape (SUGUHA: straight line) or complex representing landscapes, Chrysanthemums, and others .....
The blade is heated to around 800 ° C then suddenly plunged into water whose temperature is a secret for each master. The blade is kept horizontal, cutting edge down. In contact with water, the cutting edge cools very quickly, becoming extremely hard. The rest of the blade, protected by the layer of refractory clay, cools less quickly and thereby retains "wide flexibility".
This operation is generally done at dawn of the day, in the calm of a night that is coming to an end. For this: no measuring devices for the temperature of the water or that of the metal heated to red. The blades are engraved in relation to the hardening dates. These engravings would correspond to the periods of the year when the water temperature would be the most favorable.
The weapon is released from the clay. It is examined with the greatest care in order to detect the slightest defect. If the exam is satisfactory, the blacksmith will move on to the next step, polishing. The blade will come out only to shine with its beauty.
The concern to keep a weapon in good condition seems very old in the history of Japan. This concern arose very early in the mind of the Japanese warrior, but it must be recognized that the art of polishing did not develop until the beginning of the HEIAN period and it was the KAMAKURA period which subsequently saw the appearance of the first professional polishers.
The art of polishing made great progress under the leadership of TOYOTOMI HIDEYOSHI, who took the reins of the country in 1582. First person of high rank, he was truly concerned by the artistic value of weapons and concerned with making a work of them. of art. It is from this moment that the mounts of the sabers are lavishly crafted.
Polishing became a real art during the EDO period, which saw the establishment of specialized workshops under the leadership of the TOKUGAWA clan. The employees employed become over time of an emeritus professionalism.
In 1868, with the return of imperial power, the imperial decree (HATO REI) prohibited the wearing of the sword. it is the end of the Samurai caste.
The result is a disinterest in weapons and manufacturing techniques. Fortunately, the art of polishing does not know a big decline, but on the contrary progresses thanks to the amateurs eager to preserve the family weapons in perfect condition, and to allow the Japanese as well as the foreigners to appreciate the saber like object of 'art. Thanks to these patrons, traditional manufacturing techniques have been passed on to subsequent and current generations.
Forging and dipping are very important operations for the strength and reliability of a blade, polishing is just as important to bring out and showcase all the beauty and quality of a blade.
No weapon can, without polishing, have that luster and splendor so peculiar to Japanese weapons. A subtle paradox, an excellent blade whose polishing would have been neglected will be arbitrary, while any weapon will be attractive by the simple fact of a proper polishing.
The first phase of the work is called: JI TOGI, it consists, using a coarse stone, to cut the blade in order to remove the irregularities. The work begins with the back of the blade (MUNE) then the edge (HA). This operation is then carried out in the cross direction from SHINOGI to HA. This so-called preparatory operation is followed by the actual polishing: SHIAGE.
The blade is rubbed with selected abrasive stones, the grain of which decreases as the work progresses. Each passage removes the present traces of the previous stone. The craftsman varies the direction of his work which, from perpendicular to the SHINOGI at the beginning of the work, is oriented parallel to the cutting edge at the end of it. The tip (KISSAGI) is only worked at the last time. The realization of YOKOTE is the most important and delicate phase of polishing.
In the final stages of polishing, the craftsman no longer rubs the blade with stones, but with a paper on which he deposits a very thin layer of limestone powder (UCHIKO).
The art of polishing is to bring out the grains of steel (JIHADA) and the line of soaking (YAKIBA). This is obtained by different intermediate polishing: A burnisher gives the MUNE and the SHINOGI - JI the appearance of a mirror, while the YAKIBA and JIHADA are obtained by a slightly less fine polishing.
There are two different ways to polish YAKIBA. The KESHO method and the SASHI KOMI method.
The KESHO method is the most widespread. The polishing of the YAKIBA is carried out with a stone with a stronger grain than for the rest of the blade. The result presents a contrast which gives the YAKIBA a silvery-white tint.
The SASHI KOMI method uses the same stone for polishing the entire blade. In this case the JIHADA and the YAKIBA are practically identical in color and, therefore, very difficult to delimit.
These two methods bring beauty to the blades of sabers.