Process of Carving & Shaping a Tanto Saya

Once the tsuka is made, it is time to create a saya (scabbard) for the blade. The saya should fit snugly on the habaki, with most pressure to the top and bottom, and should hold the blade securely without rattling or jamming. The lines and proportions must be appropriate to the blade and handle and take into account the appearance of the whole unit.

Similar to the process for tsuka, a saya is shaped in two distinct stages, first the wood is split and the inside carved to receive the tang, and then it is joined back together and the outside is carved, planed, and shaped. As with the tsuka, the edge of the blade is placed slightly off centre in the block so that the edge is fully supported by wood rather than resting against the glue joint.


Carving the Inside

Creating a saya is begun by selecting an appropriate block of wood, sawing or splitting it into halves, and carving out each half to guide the blade smoothly. Carving is done with purpose designed chisels called saya-nomi (鞘鑿). The mune should be centered in the block of wood but the small flat surface for the edge should be fully seated in the omote half of the wood, slightly to one side. The purpose of this is to align the wood with the tsuka and keep the edge from splitting the glue joint if it ever makes contact with the saya.

Beginning with the omote, the carving begins at the mune and moves to the ha, checking the fit of the blade without the habaki. Once the omote fits well, the ura is carved from the mune to the ha, checking carefully and often. Finally, with the habaki in place, the halves are carved again to form the habaki area and tune the fit carefully. When the fit is just right and the blade sits in place, the two pieces of wood are joined back together with sokui (rice paste glue) and wrapped tightly with a cord until dry.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The omote half is carved first, starting from the spine and moving across to the edge. The edge sits against the inside of this half fully which puts any potential stress against wood rather than against the glue joint. Note the oil reservoir in the tip of the omote side to collect excess oil and pull it away from the blade during storage.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A look at how the two halves align at the habaki area, where the koiguchi will be. The last third of the habaki should engage and grip the wood, mostly on the top and bottom rather than the sides. Final adjustments take some time to get right.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The two halves glued back together with sokui, a paste glue made from rice.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Wrapped with a leather strap to provide tension, wooden wedges increase pressure where necessary.

Shaping the Saya

The outside work is carried out using chisels, planes, and occasionally coarse files. The block is first squared up and then taken down to the rough dimensions. The shape of the koi-guchi (saya opening) is marked and carved and then the rest of the block is chiseled down to meet it. A plane is used to smooth and true up the surface and final sanding is done with tokusa (horsetail plant, equisetum hyemale, 砥草, “to” as in togi) glued to wooden blocks with sokui (rice paste glue).

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After the sokui is dry, the block is squared up to the blade opening using a tracing of the seppa in place on the tang as a template. The taper and curvature is planed into the four sides so that the shape flows from the tsuka.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A chisel or knife is used to carve the koiguchi down to meet the outline. Then the rest of the saya is planed down to match the shape, at first roughly to eight sides. The corners are removed repeatedly until the final shape is achieved.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A fine rasp or coarse file is used to tune and adjust the fine details of the shape.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Tokusa blocks made from horsetail glued to blocks with sokui can be used for a fine wood finish, particularly for shirasaya.

Horn Koiguchi

Usually a horn or metal reinforcement is added to the koiguchi to counteract the pressure of the habaki and prevent the blade from cutting through on a rough draw. Horn is tough but not as hard as bone or metal. It can be carved with chisels or knives and has a grain-like structure to it. The method for the koiguchi is to carve away enough wood for the horn or metal to sit in its place. The habaki is used as a rough guide for making the opening in the horn, a kiri used to drill holes and then files to create the shape of the guchi.

Kurikata translates “chestnut shape” and in its basic form is the tying off point for the sageo (cord) that attaches the saya to the obi (sash/belt) so it stays in place on a draw or slip down when wearing. They are often made of horn but can also be metal or sometimes wood depending on the type of knife.

Depending on the design and material, nikawa (hide glue) or kusune (pine resin glue), or sometimes a mixture of sokui and urushi (lacquer) is used to fix these parts in place once the final lacquer work is finished.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Horn has a grain like wood and must be cut and carved in the correct direction for maximum strength.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Kurikata (cord loop) and koiguchi (scabbard mouth) carved, filed, and smoothed on the outside.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
The wood is sawn to depth and carefully carved away where the horn koiguchi and kurikata will sit, this is a patience building activity.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Washi paper reinforcement is glued along the seams of the wood with sokui.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Koiguchi and kurikata sitting in place by friction, they will be glued with nikawa (hide glue) once the scabbard lacquering is complete. The koiguchi is dished slightly in the middle, ensuring a tight fit at the mouth.

Shitaji, Preparing the Lacquering Foundation

There are two distinct stages to using urushi (traditional Japanese lacquer, made from the sap of a tree). The first stage is to prepare the base material by sealing, filling, and polishing, and the second is to coat with a smooth finishing layer. Urushi is used in several ways to prepare the surface, first by coating and wiping off, known as fukiurushi, and also as an adhesive and gap filler when blended with other materials such as sokui (rice glue) and finely powdered clay and earth.

Each time a layer is added to the foundation from one to three days are required for curing, and then the surface is wet polished and dried overnight before adding the next. The goal is to seal the surface and fill in any low spots so the final layers of urushi goes onto a smooth and even surface.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Using a thin wooden spatula the saya is coated with a thin layer of ki-urushi. After soaking a few minutes it is wiped off with a sturdy cotton cloth. Raw urushi looks like light chocolate milk but it immediately begins to oxidize to a darker and darker colour as it sits out. After a few hours the colour is a reddish chocolate. The next day it has cured enough to handle and add the next layer.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Depending on the season curing times can be very long. An urushi furo/muro is used to create favourable conditions for the curing reaction, warmth and humidity.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
For most urushi work about 25 degrees and 75% humidity will work most efficiently, though too much moisture too quickly will cause a wrinkly surface or may seal an outside skin and prevent the interior from curing properly.


Urushi, The Final Layers

There are several approaches to applying the final layer, depending on the desired finish and the style and skill of the artisan. One way of achieving a smooth surface is to paint the last layer thicker than the foundation and middle layers and allow the urushi to settle out into a glossy surface. The other is to polish the final brushed layer and then apply several coats of fukiurushi followed by a fine oil polish. Textured surfaces such as ishimeji (stone surface) can be created by various means but the most common is to sprinkle finely powdered and screened urushi or charcoal onto a wet layer of urushi and then overcoat to seal it after curing.

Each time a layer is added to the surface in the final stages, from a couple of days up to a couple of weeks are required for curing, and then the surface is wet polished and dried before adding the next. The saya is placed in a warm and humid furo, kept as dust free as possible, to ensure the urushi will cure properly.

Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
In this case finely ground and screened tea leaves are used to create the stone texture, sprinkled into a freshly brushed layer of urushi.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After the base layer is cured the leaves are saturated with urushi and allowed to cure, then peaks polished off to give the desired texture.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
After polishing, a successive thinly brushed layer seals and finishes the surface, additional fukiurushi may be applied if needed.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Extremely fine ishime-ji texture base layer using fine iron filings.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A tortoise shell appearance using alternating ares of raw and black urushi, here shown as the final layer is wet polished with charcoal and 1200 mesh paper.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A tortoise shell appearance, a very subtle variation on negoro, after final polish.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
A smooth polished surface called ro-iro requires a thicker, smoother base building process and is harder to maintain than ishimeji as it shows scuffs easily.
Island Blacksmith: Hand forged tanto made from reclaimed and natural materials
Smooth polished ro-iro surface.

The next step in the process is The Final Polish and then Final Assembly.