The Iaido Journal  Jan 2005
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Saya Repairs

copyright © 2005 Todd Forbes, all rights reserved

Recently I had the opportunity, and privilege, of repairing my Sensei's first Iaito.  The koiguchi had been well worn in, and there was a mild crack running down the ha side of the saya.  Being the traditionalist that I am, research was my first step before performing the repairs.

A traditional saya is made from two boards that have had the inside carved out to create a very close fit to the blade, without actually touching the sides of the blade itself. The mouth of the saya, or koiguchi, is carved and fitted to hold the habaki tightly to prevent the sword from rattling around in the saya. Unlike European swords, Japanese swords fit loosely into their saya, and the only part of the blade that actually touches the inside of the saya is the surface of the mune.  Once the blade is fully inserted into the saya, the habaki holds it in place with a snug fit with the koiguchi.

-- Repairing the Crack --

My first task was to repair the crack than ran down approximately 2 inches of the saya.  This crack did not violate the integrity of the koiguchi, so I luckily did not have to worry about that one.  It was said that the saya cracked while performing yonhon me tsuka ate, and I can easily see why.  Let that be a word of caution to my fellow Iaidoka.  Traditional saya are constructed so that the boards can be easily split apart to allow for cleaning and repair of the saya.  I think that is far more than any Iaidoka would want to do, and I don't think iaito saya's are constructed in the same manner.  To fix the crack, I used Elmer's ProBond.  I filled the crack from the outside and tried my best to get at it from the inside as well.  Once cured, I very carefully smoothened out the seam with a Stanley knife, to create a uniformed smooth feel.  Now I could focus my attention to repairing the worn koiguchi.

-- Repairing the Koiguchi --

Since the Heian period, saya have been made from the wood of the "Ho" tree, or Honoki Tree (magnolia).  Ho wood was used because it is soft and won't scratch the blade, and when properly seasoned it has virtually no sap in it.  Ho wood is typically seasoned for about 10 years before it is used for saya construction.  Our closest neighbor to the Ho Tree on this continent is the Yellow Poplar.  Magnolia is both strong and non-resinous, as resins and oils of certain woods can attack blade steel.  With that said, it is a good guideline to use when choosing a wood to repair a saya with.  I headed down to my local exotic wood store (Black Forest Wood Company), and picked up a block of Poplar for about $2.50, more wood than I would ever need.

It should also be noted that at no time during the saya making process is any sort of abrasive paper used.  The risk is far too great that if any residual grains of the abrasive material is left behind, it could seriously scratch the blade.  With that said, NO SAND PAPER OR ABRASIVES DURING REPAIRS!!

- The first step to repairing the koiguchi is to determine how thick of a shim you need to create.  I luckily have a pair of digital calipers, which I used to measure the inside of the koiguchi, and compared it to the thickness of the habaki.  In my case, I required approximately a 1.2mm shim.  For those who do not have calipers, just eye ball it.

- Next, I grabbed my largest chisel and chiseled off a piece of poplar approximately the same size as the habaki in width and length.  A nice sharp Stanley knife will allow you to fine tune the shim so it fits in the koiguchi.

- Rest the shim against the habaki and insert the iaito into the saya to test fit the shim.  You don't want it too tight, and you don't want to force the habaki into the koiguchi.  The fit should be snug, not tight.  If things are tight, evenly shave off some wood from the shim with a Stanley knife, and repeat until the fit is nice and snug. 

Now we need some glue...

Sokui is a Japanese glue made from rice.  Japanese carpenters made this glue by kneading rice with bamboo spatulas.  In the old days, sokui was used as an adhesive for fittings and furniture from the Nara period in Japan.  Sokui was used around the time when people stopped using hide glue, due to the introduction of Buddhism and the consequent prohibition of butchering.  Sokui is used because it is strong, but not so strong as to prevent the bond from being broken if the need arises (eg. saya repair and cleaning).

To make a basic sokui, follow these steps:

- Obtain some 1 or 2 day old rice.
- With a wet bamboo spatula or equivalent, mash rice on a cutting board.
- Add a drop or 2 of water and mash again.
- Keep adding water as needed.
- Continue to mash the rice until it becomes a stick, glutinous mass with no lumps.

You now have a basic sokui.

Advantages of Using Sokui for Various Repairs:

- No fumes.
- Does not draw moisture.
- Is strong but can be removed for repairs.

- Now that we have some glue, smear a layer of sokui on the shim and place it nicely inside the koiguchi, I placed mine on the ura side.  Press it firmly against the wall of the saya and remove any sokui that oozes from the shim.

- From lacking anything better to hold the shim press fit to the inside of the saya, I returned the iaito to the saya and used the habaki to hold the shim in place, and snugly against the inside wall of the saya.

- The iaito can be removed the next day, and the sokui should be nice and dry.  Again, carefully with a Stanley knife, I removed any dried sokui from around the koiguchi.

- With what seems to be my favorite tool, I used my Stanley knife to shave the shim a little bit to allow for the habaki to slide smoothly into the saya without catching on the new shim, but maintained the snug fit.

Eventually, the new shim will compress a bit and the fit will not seem as snug.  If it becomes too loose again you can try adding a shim to the omote side as well, but still be careful not to make it too tight.  Just remember; never force the habaki into the koiguchi, snug, not tight.  If you ever need to reshim your saya, always remove the old repair.  The use of sokui allows for easy removal of old shims.  If you were to use ProBond or any other wood glue, or other adhesives for that matter, the repair would be more permanent. 

Overall, I consider the repair successful.  One may question the strength of Sokui, but the bond is amazingly strong.  If I were to say anything to anyone who wished to do repairs on their iaito, I would recommend they research the operation they wish to perform.  More than just an understanding of what you need to do, but as well as an understanding as to why you are performing a repair a certain way, and how it relates historically in a traditional sense.

-Todd Forbes is a member of the Calgary Muso Shinden Ryu Iaido Club 

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TIN Jan 2005