Full Wrap Samegawa

In this tutorial I will demonstrate how I apply a full wrap of samegawa (ray skin) to a bare tsuka core.  There are a lot of different methods of applying samegawa to a tsuka and after experimenting with many of them, I have chosen this one because I feel it’s both simple and effective.  As with any of my tutorials, there is room for personal preferences and you should change things as you see fit.
While the most common form of samegawa found on modern production swords are panels running down the center of both sides, I felt that applying it that way is pretty self explanatory so I focused on a lesser known way to add the beauty of this amazing skin to your katana.  When it comes to a full wrap there are a few locations to place the seam, the most commonly seen way on antique nihonto is for the seam to run down the center of the ura side.  Many people these days choose not to have the seam visible and therefore want it hidden under the tsukamaki on the side of the core. This will be the way I’ll show you here.
What are the benefits of a full wrap?

There are a few reasons samegawa is used on katana tsuka and perhaps the most obvious is for the aesthetics, there’s nothing quite like the clusters of pearl like nodes when they’re nicely polished.  In addition to looking nice, and certainly being unique, is the incredible strength this natural and versatile product provides.  There is not much that compares, whether in nature or man made. Not only are the nodes as hard as teeth but the skin has an amazing ability to shrink and compress when soaked and dried thus providing extra strength to the tsuka core.  Panels alone do not offer this.
The nodes also provide grip for the wrapped ito preventing the cord from slipping as well as traction for your fingers. Fully wrapping the tsuka with samegawa also protects the wood from moisture and liquids, especially when lacquered.  These are all good reasons why the Japanese chose to use this incredible skin on the katana and why there is not much, if anything, that would be better to replace it with today.

 

Which Samegawa to Choose?

Choosing the right samegawa can be confusing especially because it’s referred to by so many different names and available in many forms.  Samegawa is also called samekawa, same, ray skin, shark skin, and shagreen.  While all of these can mean the same thing, sometimes these terms can also mean something else completely or might not be as clear as we’d like depending on where and how we see it being used.
Typically, for the wrapping of a tsuka core you would want to use raw, naturally air dried skins that have not gone through a leather tanning process.  To make things easier we also would look for the skins to be lightened or bleached since they start out naturally dark in color as well as for the undersides to be scraped clean of any excess flesh.
When purchasing from sellers who cater to those who work on katana tsuka, these extra steps are usually already applied.
Shagreen

There is a large amount of ray skin used in fashion and upholstery and is easily available in places that deal with leathers and fabrics but these skins are usually of the tanned version and often referred to as Shagreen.  While these can still be used on tsuka, they are usually better for panels or other decorative applications.  They lack some of the properties and qualities we would look for such as the ability to constrict the core when soaked and dried(at least not without a lot of scraping first), a surface that is able to be dyed or easily lacquered, and a prominent emperor’s node.  The surface of the tanned samegawa is usually highly polished and the larger nodes are most often sanded flat.

Detail of central nodes on a typical tanned shagreen

In addition, these skins come already treated with coloring which is very glossy and hard to lacquer over without a lot of prepping, and the leathery undersides are very thick and would require complete stripping before using as a full wrap.  If the skin is too thick it requires removing more wood from your tsuka core which in turn can possibly weaken it.  You should also make sure that you know how much wood is between the nakago and the samegawa because some of the production tsuka out there should not be thinned for a full wrap and it’s hard to tell the quality of the construction if you didn’t make it yourself.

 

What grade and size is right for the job?

When purchasing raw samegawa you will notice that there are many grades to choose from as well as different sizes available.  There are some sellers on ebay that offer raw samegawa but be wary because many of these skins are of low quality and small size and might not be suitable for the type of wrap you would like.  A good skin should have attractive nodes that are as large as possible as well as closely packed together leaving very little open spaces between them.  The emperor’s node should also be as large and as white as possible, lower quality samegawa will have small and very yellow emperor’s nodes.

Row stone rayskin

There is a narrow style of samegawa known as row skin, row stone, and row spine among other names. While these are attractive since there are many large nodes in a row, they are often too narrow to fully wrap a tsuka core and would be better for panels.

The overall size of the skin you need depends a lot on where you would like to place the large node on your tsuka. A common position for this is right at the top of the end knot and within the same open diamond on the omote side of the finished tsuka (near the kashira). This is completely optional though as there have been many different placements found on historical examples as well as many not even displaying an emperor’s node at all.
If you would like the node in this common position then you will need the skin to be at least 20-24″ for an average length tsuka of 10-12″
This example of a raw, air dried and bleached samegawa skin is approximately 22″ long overall and 12″ wide at the center and is sold as a number 2 skin from Namikawa. As you can see, the lesser nodes are medium to large and closely packed with little open space in the key area and the emperor and secondary nodes are large with good shape and coloring.

The important area of the skin for this purpose would be from the emperor’s node to the tail end (the end without the “eye holes”) and should measure roughly 10-12″, or a little longer than the full length of your core, as seen here

There will be three nodes that are typically larger than all of the others starting with the emperor’s node and continuing toward the tail. With the best quality skins these three nodes would be spaced far enough apart so they would each appear in the center of their own tsukamaki diamond – such as in this example on a tsuka wrapped by Japanese tsukamaki-shi Yasuo Toyama –

but those skins are extremely expensive and out of most of our budgets for production sword customization.  These nodes along with most all of the others will have tiny hooks on the top of them which can be very sharp and rough on your skin as well as on the ito.  The skins can also be a little dirty from storage so to remove the hooks and dirt requires a bit of prepping before you do the tsukamaki.
This is done traditionally with an assortment of brushes, powders, and pastes and a lot of elbow grease.  I have used stiff natural bristle hand brushes as well as metal bristle brushes and silicone carbide powder to achieve a basic polish.  Since I work mostly on inexpensive production swords, it’s not worth putting in hours and hours of prep polishing as this would drive the costs way up.
The nodes as they appear before any prep work.

Tools

Calipers/Ruler – You’ll need something to measure before you cut, calipers make certain things easier but a standard ruler will suffice.

Tin snips/Utility knife – The raw samegawa is incredibly tough and regular scissors just won’t cut it (pun totally intended). I use my trusty C.A. edc most of the time as it’s one heck of a tough & sharp blade for cutting and scraping but for this demo I am using a standard pair of tin snips available at any hardware store to do the heavy cutting. You could also use a strong pair of poultry shears.

Rotary tool – I use this tool with a cutoff wheel, sanding discs, drill bits, and grinding bits.

Clamps – I use a couple of clamps to hold the drying samegawa in place

Files – They come in handy to thin the skin in certain areas and to prep the core and for final trim and smoothing.

Cord/Ito – I mainly use old cotton ito to tie up the skin as it’s drying but strong cord or twine will do as well.  If using old ito, try to avoid using the synthetic type because it doesn’t breathe and will delay the drying process.

Needle/Jewelers files – These are useful for precise adjustments, such as removing the hooks on the larger nodes, and for sizing the mekugi-ana.

Glue – I’ve used marine epoxy many times in the past and highly recommend it because it is very strong, waterproof, and gives you plenty of time to make adjustments before it sets (about 2 hours).  I am currently using the same wood glue I use for constructing the tsuka however because it has many of the same properties, plus you don’t have to mix it.  The only major difference is that the wood glue sets much quicker so you have to be precise the first time.

Strand of non-stretch ito or similar material – I use a couple of strips of remnant Tsunami ito to measure and mark on the circumference of the core because it does not stretch but you can use a fabric tape measure or other similar item.

Total project time excluding drying time should be around 2 hours.

Step 1 – Sizing

I will be placing the emperor’s node at the top of the omote end knot for this demo so I first need to determine just where this will be on the tsuka core.  Since the top of the end knot will fall at approximately two increments (calculated by measuring the stretched ito strand) up from the kashira or roughly 17-18mm for Japanese silk ito sold as 10mm. The node should be in between the top of the knot and within the opening of the tsukamaki diamond.
Once I have determined the position I will mark it.

First I mark approximately where the seam of the samegawa will be on the core both near the kashira and fuchi end on the side of the core. I then take a strip of tsunami ito a few inches long and wrap it around the core at the kashira end starting at the mark I just made and crossing over the omote side, and then marking off where the emperor’s node will be and lastly, where the seam mark is at the other end of the ito.

On the underside of the full piece of samegawa I will make marks of the larger nodes as well as drawing a line running straight down the center of the line of nodes for the length of my tsuka, this will guide me later on.  If you will not be lacquering the samegawa black afterward, do not make these markings in anything very dark and permanent because they will show through the white skin.  Then mark off where the ends of the core will be.

Align the mark you made on the ito representing the emperor’s node to the center of the actual node on the underside of the skin.

Now mark off where the ends of the seams will be.

Now do the same thing near the fuchi end of the core and mark them off on the skin at the appropriate spots. Instead of using the emperor’s node to determine the center, just mark the center of the core on the omote side by measuring with the calipers/ruler and align the mark on the ito with the line you drew down the center of the skin earlier.
(I’m using a different color here)

Now I like to add an 1/8″ of width to each side giving a total of a 1/4″ extra width just in case there is excess shrinkage when drying. There is not much worse than having the samegawa come up short leaving ugly gaps in the wrong places after it dries.

Holding the core in the same direction it will be when wrapped, use the mune side of the core to draw the edge line on that side and ha side of the core to draw the other line. Also draw the lines at the fuchi and kashira to connect with the lines for the sides.

And when done it should look like this

Step 2 – Cutting

Use your tin snips, poultry shears, or utility knife to cut out the pattern you’ve drawn. You can even use the rotary tool for this but be cautious because it can cut too quickly sometimes and accidents can happen.

Step 3 – Thinning

Depending on the state of the piece of samegawa you’ve purchased there might be some thinning to do, especially where the larger nodes are and around that general area. The skin is naturally thicker here and even when soaked this part can be very difficult to bend. It can also cause bulges later on that will show in your finished tsuka so you might need to both thin the skin and do some filing on the core before you permanently glue the samegawa down.
I find it easier to thin these areas with a file when the skin is dry because when wet, it will be like filing pulp. Don’t remove too much, just enough to even it out with the rest.

Step 4 – Soaking

Fill a bucket or bowl with enough water to cover the piece of skin and drop it in there. The water should be about room temperature, never put the samegawa in hot water as it will break it down and disintegrate it.
Soaking time depends on the water temp as well as the thickness and quality of the samegawa so always check it as it soaks. 

When the piece is finished soaking, pat it well with a towel to remove the excess water.  It should not be dripping wet when you wrap the core because this can damage the wood.

I put this piece in for about 15-20 minutes until it was pliable and easy to roll up.

 
Step 5 – Initial fitting

I personally like to do two fittings, a preliminary and then a final but it’s not absolutely necessary.
This is where this process gets a little painful, you might want to wear some work gloves for this part because the surface of the samegawa is extremely rough on your skin.
Align the emperor’s node with the mark you’ve made on the core and proceed to wrap the skin around the tsuka.  Once it’s in position tie it on with the old ito or cord so it’s secure, it doesn’t have to be perfect or extremely tight but you might need to reposition as you’re tying because it will tend to shift.  Once it’s tied off, let it dry overnight or until completely dry.  The skin will shrink a little to a lot depending on thickness, etc.
I use some wadded up washi paper to place at the ramps and apply pressure with a clamp to make sure the samegawa conforms to the shape.

Step 6 – Trimming

Now that the samegawa has been fit and dried you will know how much excess material you need to trim off. I mostly use my rotary tool and a cutoff wheel for this but you can use the tin snips instead. Try to keep the lines fairly neat so they line up well. Once it has been trimmed, I give it another very short soak of about 3-5 minutes before re-applying just so it’s slightly flexible.
Step 7 – Gluing

Make sure your tsuka is free of sawdust or any other debris and then spread your glue of choice on the core. Avoid getting it inside your mekugi-ana or anywhere else you don’t want it. You don’t need a lot of glue, just enough for a thin and even coat.

Step 8 – Final wrapping

This time around you want to make sure you are wrapping the samegawa as precisely as possible.  You might want to make some marks on the skin and the core where they’re visible so you can make sure things don’t shift too much.  Sometimes no matter how many precautions you take, the skin can still shift a little while drying, after all it’s a natural and slightly unpredictable product.
Wrap the ito or cord as tightly as possible and use a couple of clamps to hold the positioning, as well as to maintain the depression at the ramps as you did before.  The process of wrapping and shifting the samegawa is not one I look forward to because it really is torture on your hands so again I would recommend wearing some type of durable work gloves.  If your core is on the thin side or if you didn’t carve it and you’re not sure of the construction, you might want to have the tsuka mounted on the nakago for this step so the compression of the samegawa doesn’t crack the core.

Step 9 – Drilling mekugi-ana

Now you will drill and shape the mekugi-ana in the samegawa to match the ones in the core.  I use a powerful light placed at the hole on one side of the core while looking at the other side and I can then see where the hole is.  Mark this in the center and then do the same on the opposite side. Begin drilling with a small bit and progress from there with larger bits or a conical grinding bit on a rotary tool.
Finish the final shaping by going slowly with a round needle file so you don’t accidentally remove any of the wood and make the holes too big.  I like to do the final shaping while the tsuka is on the nakago.
Make sure that your mekugi fits properly.

Step 10 – Filing the ramps and edges and polishing

Before tsukamaki you will cover the ramped areas on both sides of the core with paper but I prefer to smooth these areas out first so the paper covers more evenly.  A smoother surface will also make it easier to thread the ito during the final knots so take your files or sanding disks on your rotary tool and carefully smooth these areas.
I also like to smooth out the ha and mune edges of the tsuka somewhat because I will also be placing paper strips along these before tsukamaki and this makes it a little easier to do.
Now is when I usually do the cleaning and polishing of the nodes with assorted brushes and powders.  My goal is to make the nodes a little less abrasive and to remove any dirt or marks from the surface areas that will show through the finished tsukamaki.
(you can see in this pic that I’ve already polished the tops of the larger nodes)

Step 11 – Optional lacquering/sealing

You can wrap the tsuka without any lacquer if you wish or you can use a number of different products to give it some color or sheen and to seal the samegawa from water and moisture.  If I want a “naked” look, I usually give it a couple of coats of clear satin polyurethane but if I want a shinier look I use the high gloss version.  For black I use black Japanese cashew lacquer as I find it’s much more durable than regular spray paint.  I’ve also used dyes on a couple of occasions with great results.
For this particular tsuka I want an aged/antique look to the samegawa so I’ll be using a transparent Japanese cashew lacquer which will give it an amber tone.  The more coats you apply, the darker the tone will be and be careful because the tone also darkens as it dries so add the coats one at a time letting it dry in between.

You’re done! 

I hope this is helpful to those interested in wrapping your own tsuka and hopefully this process doesn’t seem as intimidating as it might have before.

If you’ve enjoyed the tutorials and feel like buying me a cup of coffee, a meal or more tools, I’ll be super grateful. Thanks!

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