Proportions of the blades

Recently I have finished an order that was a bit different from the others. The client brought a blade and I was supposed to polish it and make a koshirae (set) for. Its robustness was roughly half compared to my blades. Also most of the batch production swords have delicate blades which do not reply much to the characteristics of a new sword.
The reason might be old antique blades as models. Those are very often “tired”. That is why the next lines are going to explain the difference between old and new blades, rather blades in use, repeatedly repaired and newly produced swords.

It is not really possible to clearly say what should be the exact proportions of a newly produced sword. It is of course necessary to consider the type of the sword (historical period). Here are evident differences in shape that was influenced by the way of use. So the description is rather orientation.

Width and length of the blade

Width by nakago between shouldered tops of the edge (hamachi) and back (munemachi) is called motohaba. The length is called motokassane. The proportion before the tip (kissaki) between the back (mune) and the edge (ha) is sakihaba and length of the blade sakikassane. Ratio between the proportions by the tip and shouldered tops by the nakago is approximate rule of 70% by the tip to 100% by the machi. This is for both, width and length (kassane). So the blade is narrowed towards the tip for approximately 30%. This rule is not a dogma. For example some sword-cutters are making blades that have even kassane at full length.
I am usually making blades of these proportions – length approximately 76cm, motohaba 34mm, sakihaba 25-27mm, motokassane 8mm, sakikassane 6-7mm.
These proportions are in upper maximum for usually produced swords.
The high of the shoulder of hamachi and monemachi is approximately 2,5mm. This proportion is good to follow with antique blades. There is clearly visible how both shoulders were being lowered while restoring. Hamachi is often much lower than munemachi although there are even on the new sword. The reason is simple. The edge gets more wore (by using) than the back. If the blade had been thru some major restorations like removing the chips after the fight (hakobore), hamachi would have extinguished and the edge would have smoothly merged into the same level with nakago. Of course it was necessary that the line of hamon reached high enough and was kept in at least minimum high at full length of the blade.

Ubuha

Part of the blade, approximately at first fifth behind hamachi, is blunt, rather the edge is plane (about 1-2mm), to avoid hamachi being grinded away too fast. That means that during the first restorations the blade gets thinner by the tip (monouchi), also ubuha gets thinner, but hamachi is not getting lower. Ubuha disappears after a few restorations and the blade is than sharp at full length. But proportions ratios had already changed at this stage. On the contrary to the new blade, such restored blade is way thinner in direction from the tip. That gives the blade very elegant shape compared to the robust shape at the very beginning of its career. Of course every specific changes of the shape caused by reparations depend on the seriousness and way of damage (for example location of the chips).

Hiraniku

It is proportion that marks curvature of the plane between the edge and the middle rib (shinogi) or the edge and the edge of the back at hira-zukuri blades. In a perfect stage it has a shape of an even lens. Size of this proportion (niku) has a direct effect to the blades features. It affects the ability to cut and its resistance to the chipping. The more hiraniku is plane the thinner is the wedge that forms the planes of the edge, so the sword is also sharper. On the other hand the resistance to defects is lower. On the contrary, the blade with robust hiraniku is more resistant but the sharpness is not so high. The niku shape of a newly produced sword always depends on the producer. I am always deciding according to the purpose the sword is meant to be made for. If the customer wants to practise tamechigiri and cut straw, the niku will be usually smaller then the niku on the sword that is not supposed to cat anything. From my point of view, it is a pity that many students of Japanese fencing prefer very light and very sharp blades. To make 76cm blade with characteristics mentioned above and weight 800g actually means to make already tired blade with almost flat hiraniku. If such sword had been thru battle where it should cut thru an armour and clash with other swords, it would has most probably never been usable again. Some batch production swords have no hiraniku at all and the planes that form the edge are flat. Resistance of such razor sharp blade is very low, even straw cutting can cause chips. However polishing of a flat plane is easier than polishing of a lens shaped blade, especially if you want to keep shinogi. That is maybe the reason, why some types of the blades have such edge. Let´s get back to changes on the shape caused by detrition. Newly produced sword has bigger hiraniku than the repaired ones.

Hamon

Newly produced sword has balanced hamon. It usually gets a bit higher near hamachi. Then, after short section, it continues in a same high up to monouchi (last approximately 20cm of the edge) where it can get a bit higher again. Then it goes along the fukura line (curvature of the tip). This description is just one of many and it is chosen to make further detritions easier to be described. On the contrary some sword-cutters let the hamon go down in monouchi part, evidently to lower the risk of breaking the sword in its most stressed part. And there are more different variants. In this mentioned case, repeated polishing of the blade lowers the hardening mostly in monouchi. At the end the line of hamon gets due to reparations much lower. Also the shape of the tip gets changed. Minimum of the material should be removed while repairing. So if the top of the tip had been broken you would have done only necessary correction (rounding of fukura). That is why the old blades tips often very round are. There are various opinions on the original shape of fukura. Some say that the round shape was formed already during the processing; the others prefer the idea of abrasion during using. One type of kissaki (the tip) is kamatsu kissaki, where the line of fukura is almost straight. This type exists in three variants – short (ko), middle-sized (chu) and long (o). In my opinion, the shape of the tip is influenced by the personal taste of every sword-cutter himself. The tip is anyway the most beautiful and as for the making processes also most difficult part of the sword.

Mizukage

This effect is worth to mention. It originates during hardening process. It looks like a shadow, going from the edge diagonally up. It usually appears before the line of hamon. Mizu kage (shadow of water) originates as a line of souse. If you souse the whole blade including nakago, this effect will not appear. Some old swords have the hardening starting a few centimetres behind hamachi. These have often very clear mizukage. If it appears on short blade it will be a sign that the blade was re-hardened. Other way hamon would have continued on nakago. Some sources describe mizukage as a defect on the blade. This is understandable with re-hardened blades, while groundless with original and newly produced blades.

Zkracování

There could be a few reasons for shortening. There was couple of decrees, rather orders in Japanese history, which regulated allowed lengths of swords (article by Jakub Zeman – Wakizashi (Fighters magazine 1-2/2007)). And of course personal reasons of the owner, to whom a long blade might not suited.
Shortening always starts from nakago, never from the tip. In that case a newly shaped tip would be without hamon line and as a consequence it would damage the blade.
Shortening means cutting a necessarily long rear part of nakago and accordant shifting the shoulders hamachi and munemachi.
If the shortened blade had had a signature of its maker, it would have moved to the end of nakago, or in case of larger shortening it would had totally abolished. If the owner had wanted to keep the signature it would have been possible to cut it out from the removed part of nakago and then embed in the newly formed nakago (gaku mei). There is a possibility that the blade signed like that was actually signed by the signature removed from other blade (for example destroyed by fire) of higher quality to rise its price. In case of doubts it is necessary to study the signed sword-cutters work for the characteristics to compare it with the blade on which the mei is.
Another option to keep the mei is trimming the mei around without its complete separation from the original blade, and turning it on ura side of nakago (orikaeshi mei).
Shortened blades were not to be signed again (by cutting out) because every sword-cutter has his own signature – authentic not only by its look, but also by the character, location of the signature etc. Some blades have been signed with gold or red lacquer, in dependence on whether it was signed while shortening or the author was additionally added by expert.

Satsumaage

This is not really well-known way of correction of the broken blades. There were two possible reparations. The first – making a new tip (weapon with non-hardened tip – functionally limited). Nevertheless present collectors and dealers are using this way because of its ability to at least partially save the character of the damaged blade. But the value of such blade is much lower. The second option was creating a new blade by smooth lowering the back all the way to the edge. That creates a blade with crow pecker tip (satsumaage). Original shape was completely changed, however the tip stays hardened so fully functional. I take it that from the present collectors and sword restorers point of view such step would be considered unacceptable and even destructive. But as from the users point of view it is undoubtedly recovering of the blades (expensive) functionality. The blade would have been useless to battle if it had been repaired the other way.