Here is a quick and simple way to help strengthen your tsuka-ito after it’s already wrapped on your tsuka.
I use this method mainly on genuine silk but I have also used it on nubuck leather and Japanese cotton with good results and it can also be used with synthetic silk ito. I always recommend testing on a scrap piece first.
You can achieve different results from stiff but still soft on the surface, to almost completely solid and plastic-like depending on the number of coats you use, the technique with which it’s applied, and the viscosity of the mixture.
I will be demonstrating the first example, stiffer ito while still fairly soft on the surface, as it is what feels best to me. I will also be using polyurethane since it’s generally more accessible and safer to use than urushi lacquer.
WARNING – Adding lacquer to your ito will darken the color. Always test first!
What you will need
Polyurethane – I usually use fast drying clear semi-gloss polyurethane, such as Minwax brand but any equivalent should be fine (always test first)
Mineral spirits – Or recommended thinner based on your lacquer (read label), odorless makes it more tolerable in my opinion.
WARNING: Do not use mineral spirits if your tsukamaki was done using kusune (pine resin glue). Mineral spirits and other thinners can dissolve the kusune and make the glue ineffective. Most production katana tsukamaki does not include traditional kusune but thinners may also dissolve modern glues that might have been used instead. always test first.
A small to medium size artists paint brush – This is really just a personal preference but I like having more control so I go with a smaller brush. Make sure the bristle type is recommended for your lacquer and thinner.
Rubber gloves – I use standard latex or chemical resistant rubber gloves
A stand – Or something suitable for holding the tsuka while you apply the lacquer. I use a thin wood shim that fits in the nakago-ana and the other end gets clamped in my vice
Step 1/A – Making a test strip
I always recommend making some test strips if you’re not familiar with the mixture or the ito. Follow the steps below on a small piece of spare ito, let it fully dry, and see if it’s to your liking. You can see here that I applied the mixture to approximately half of a spare piece of the same silk ito I used on my tsuka. The color tone is slightly darker where the lacquer was applied and it is clearly a bit stiffer there as well. Notice in the second picture the lighter color to the right of the arrow.
Step 1/B – Mixing the liquids
You may not need to use thinner, especially if your lacquer is new and thin already. If it pours easily and is slightly thicker than water but not slow pouring and gooey like olive oil, you probably don’t need to thin it.
There is no real rule to the ratio but I tend to use 3 parts polyurethane to 1 part thinner. What you want is to have the mixture thin enough so it easily soaks into the fibers of the ito but not too thin where the lacquer isn’t effective as a stiffener. You can experiment to see what works best for you so always test it first. Some products are thicker or thinner than others. I usually have a batch already premixed in a sealed jar. Make sure to stir this well. In the case of a brand new can of polyurethane, it is usually thin enough where I can use it without thinner. Again, it depends mostly on the consistency of the liquid.
Step 2 – Applying
Tape off any parts you don’t want lacquer on such as the fuchi (if attached permanently) or kashira, or even menuki.
Carefully go over each area of the ito little by little making sure you get enough lacquer on it but try to avoid repeated applications on the same areas. Depending on the color of your ito, you might be able to see where you have already applied it but on darker colors it might be difficult to see this clearly. You may want to use tape or some other method of marking where you’ve been so you don’t over-saturate. I usually try to lacquer one set of two strands of ito across one side of the tsuka at a time.
You can see the tone darken here
Be sure to get in all the creases and under the folds as much as you can
Keep going until you’ve covered the whole tsuka on both sides with an even amount of the mixture. You basically want to see the mixture on the surface when applied and then see it get absorbed into the fibers until it no longer is sitting on the surface. If you’ve applied too much and it won’t absorb any more, try to remove some with a wadded towel or a dry brush.
Step 3 – Massaging the ito
This is a critical step if you don’t want the surface of your ito to be hard and feel like plastic when dried. Once you’re completely done brushing on the lacquer, immediately begin to massage it into the fibers with your fingers (wearing gloves) going over the whole surface of both sides. You’re goal is to evenly distribute the lacquer mixture all the way through the ito from top to bottom. Try to avoid pushing too hard and disrupting the folds of your tsukamaki.
Step 4 – Let it dry
This is perhaps the most important step and also the one that gets rushed too often by some. You must let the tsuka fully dry to see if you need another round or not. I usually let this dry overnight. If it’s not fully dried it can feel like it’s too loose and needs more but what you’ll wind up with if you rush it is too much lacquer and it could then wind up being much harder than you would like. Be patient.
If when it’s fully dry it still feels too loose to you, you can give it another light round by repeating the steps above and then let it dry again. I find that one good round is all I usually need.
You can see the finished and fully dried tsuka here along with the original test strip. The color is now slightly darker than it was before. The lower portion of the test strip was not lacquered. The tsuka in this example still retains the smooth and soft feel of fine silk ito but the folds cannot be moved.
You’re done! If you proceed carefully and make sure to test before you apply it to your project, this should be pretty fool proof. Feel free to experiment with the mixing ratios, products, and technique to see what feels most comfortable to you.
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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