Koiguchi

I thought it might be informative to take a little closer look at the koiguchi of the saya so that a better understanding of how it's dimension is established and how it translates to the overall balance of the saya.   The creation of a koshirae saya requires very careful thought both in theme and style.  What is often overlooked in the western world is the proportion of the kodogu in relation to the blade and the style of koshirae chosen.  The blade once forged and shiage polish completed,  goes to the habakishi for habaki.  The habaki is critical in the overall balance of the koshirae and should not be skimped on. When kodogu is being considered for a blade one has to take into consideration the the habaki size and how it compares with the fuchi chosen.  The Goto established early on the dimensions utilized for the construction of fuchi kashira and when examined closely there is very little variance in their dimension of kinko fuchi kashira or schools established by those trained in their style.  There are some variations and a very large blade will require something out of the norm.  The saya koiguchi and the fuchi should be on equal plane with one another or with just a very slight step down from the koiguchi to the fuchi. This trait is inherent to Higo koshirae and is most apparent in this style. This is key in determining a koshirae made outside of Japan or one of lesser quality.  In order to establish this relationship between the koiguchi and the fuchi it is required by the sayashi to incorporate techniques that will allow this transition and still provide a strong saya.  When the relation between the base of the habaki and the fuchi tenjo gane are such that there is a minimal overlap or none at all, than one should reconsider the size of the kodogu chosen and would be best served by something of larger proportion. when proportions are marginal there are several ways to establish a balanced relationship between the saya and the kodogu chosen

Most of us are familiar with the use of horn for reinforcing the koiguchi.Horn does provide a quality reinforcement but requires the removal of stock from the saya so that there will be enough horn material present to prevent the horn from splitting. If the there is no stock available to be removed than some other method must be incorporated.

The simplest method of reinforcing the koiguchi involves the cutting of  a 1.5  mm wide channel around the circumference of the saya approximately 5-6mm down from the koiguchi edge.  This channel is than bound with a hemp cord of small diameter and glued.  Tonoko (a filler) is than added and than the saya is lacquered.  The final appearance of a horn koiguchi is established by skillful use of lacquer.

When tolerance is at the extreme and there is no room for even a small recessed cut like that mentioned above.  Hemp is again incorporated but the time used as a flat band that is wrapped several times and than glued.  This will provide strength and a minimum amount of relief to be overcome in the process of lacquering.  The koiguchi is than lacquered like above. I had completed a tachi koshirae restoration of considerable proportion with this method When the blade was removed from the saya one would think that the blade would be unable to fit this saya.

Koiguchi reinforced with iron or some other metal are a very versatile method of providing substantial strength and still keeping the tolerance around the habaki minimal.  When the band is of a non decorative type it is generally hidden by using methods mention above.

Most other methods of  koiguchi reinforcement are variations of the methods above.

Koiguchi Project