Ok, so today I'm going to talk about at suriage. It's quite an in depth subject as it happens so I'm not going to go into depth, but by the time you're done reading you should have a good idea of what its all about. In a nutshell, suriage means to shorten a sword, it can also be used to describe a sword that has been shortened. This largely refers to katana and could mean that anything from an inch to several inches was removed from the overall length.
To many people, shortening a katana would seem odd. I mean why on earth would you take something that had been purposefully forged to a certain length only to lop inches off its effective range? There were in fact, a few very good reasons why this was done. For example, during the Edo period, a limit was imposed on swords which restricted the length of the katana to 2 Shaku 8 Sun or around 87cm. A lot of samurai could simply not afford to purchase a new sword and so would opt to shorten the one they had. I would of done the same. Perhaps the sword had been horribly damaged near the tip and could not be repaired. An uncommon practice was to shorten from the end of the sword, thus bringing the tip back past the damaged area. In order to accomodate the hamon of course, this resulted in a much shorter blade as material was taken from the back of the blade as well.
An example of how a longer sword with substantial damage to the ha could be dramatically shortened at the back to produce a much shorter but still very useable weapon. In this case the nakago has been shortened as well.
Another possible reason was that by shortening the sword at the nakago end, you could remove the drastic curvature at the base of a tachi and accentuating the curve at the end. This shift from koshi-zori to tori-zori would also mean that you ended up with a sword that was more katana like in its curve distribution.
A Tachi, before o-suriage, exhibiting koshi-zori, or most curvature at the base of the sword.
The tachi now has the nakago greatly shortened. You can see how this affects the overall curvature almost immediately. This kind of large shortening of a sword is called O-suriage.
Now, the machi are moved further up the blade. Because of the heat treatment, areas of the sword have to be heated and softened before this can done and you can see how this can affect the hamon. The second mekugi-ana would not be drilled until the tsuka had been made and fitted but I have added it to further illustrate the process. At this point, the curvature has moved so far up the blade and enough fumbari has been lost as to make this look almost like it had been a katana to begin with.
It's also interesting to note that not only were katana candidates for suriage, but wakizashi and even naginata were too. The term isn't limited to one category, many blades have found themselves being repurposed by shortening and so the reasons were varied; but whatever they were, suriage was a relatively common practical occurence, a consequence of the amount of labour put into the creation of these weapons as well as the cost. Swords were not cheap and it was nearly always less expensive to repair or alter one than to have a new one made but still even this process was anything but easy. The katana is a well engineered piece of metal and in order to keep it looking and functioning at its best, considerations had to be made and that meant that different methods had to be employed in order to properly suit each type of blade and reason for suriage in the first place.
The basic procedure
Most of the time, the process started at the nakago where it would be shortened by removing a piece from the very bottom. Then the machi, or the part of the blade that the habaki fits into, would be moved upwards determining the length of the cutting edge.
In order to keep the proportions of the sword correct, the thickness of the nakago would be filed down. Normally this would only happen to one side, but sometimes simply thinning one side would not give the desired results and if that was the case then both sides were altered. This was not the best outcome of course and I'll detail why in a bit.
Because of the decrease in the thickness and width of the blade the further toward the tip you go, it was possible that the habaki would have to be altered or remade as well.
All of these alterations would hopefully provide a sword that was still well balanced but shorter than it was before. oh, on top of all this, the tsuka would have to be remade in order to accomodate the modified nakago and so you'll see the whole procedure is not a light undertaking.
Preservation of the mei
When a blade is shortened, the thickness of the nakago (the tang of the blade) must be reduced in order to keep the proportions correct. This is usually done by reducing the thickness of just one side in order to keep the unsigned side untouched. This way the sword can still be attributed to the original smith which was (and still is) very important especially if the smith was well known for his work.
A sword with Mei, everything else being equal, is also worth more than one without.
Interestingly enough, even if the nakago carries no such Mei, the shortening process would normally preserve the side of the nakago that would carry the signature. This is good news for collectors of course as the patina that develops on there is a useful indicator of the age of the blade. Now sometimes the signature is present but the process of shortening the sword would mean that the Mei would be damaged or even cut right off, but fortunately there were methods of preserving this signature in the event that it would be damaged. It could for example, be cut out and inlayed further up the nakago. Again this is a blessing because so many swords were shortened that were it not for the preservation of the signature, attribution would be so much harder.
Considering the Hamon
The hamon is the pattern on the blade that is created by the differential heat treatment imparted to all traditional Japanese katana. It is created when the spine of the blade is forced to cool at a slower rate than the cutting edge and creates a very hard steel structure that is incredibly hrd to simply grind away. For this reason if needed, the part of the blade to be removed can be heated beforehand to soften the steel making it more easily workable. This can have the effect of reducing the appearance of the hamon however which cannot be easily remedied because re heat treatment of a small portion of the blade is tricky to say the least.
So, although suriage was no easy task, there were definite reasons for doing it although they did vary greatly. Sometimes the reason for the shortening was less than honest. If you took a blade for example that was made by someone who wasn't well known, the blade could be shortened, or even made to look like it had been shortened and the owner could claim falsely that it was in fact made by a much greater smith than it had been. This was apparently not uncommon.
At the best of times the practice of suriage places places an extra hurdle between official appraisers and their identification of many old swords, but it also adds history to the blade. To think it was not only used, but greatly modified giving it new life so it's owner could continue to use it is pretty amazing and to own such a sword must impart no small feeling of awe.