The Iaido Journal Aug 2007

Finishes for Wooden Weapons

copyright © 2007 Kim Taylor, all rights reserved

One of the most common questions I get as a producer of wooden weapons for martial arts is "how do I take care of my weapons". This is a quick consideration of what is coating your weapon, how to take care of it, and how to repair it when it needs to be fixed.

The finish on wood is there for a couple of reasons, to protect the wood from the elements, sun, water, and humidity changes, as well as to protect it from spills, scratches and other damage. Finishes on outdoor products may include UV blockers to reduce fading in the sun, and pigments to stain the wood. Modern furniture generally has a urethane finish which is quite tough and hard.

For martial arts weapons specifically, our desired result for any finish is that the wood be protected from humidity changes, and that it should have the desired "feel" on our hands, that it should have the right combination of slide and stick. Personally, I like a finish that is fairly smooth without being sticky. My hands and feet don't seem to sweat much, but if they did I might actually want a finish that is less resistant to water so that the wood would soak up the excess sweat.

Which brings me to the often quoted advice on finishing a stick... "Blood and Sweat". I usually counter that with "Moisture and Warping" but actually a piece of wood, if left long enough, does develop a fairly good finish, as has the pine trim in my house that I never quite got around to varnishing. After 15 years it's a lovely honey colour and is even pretty resistant to dirt. The sweat off your hands has some oil in it, and if you use your weapon often enough to "finish" it (which is what sensei is saying when he says "sweat and blood") you will build up the oil. A similar finish is often seen on the hilts of hand made work knives that are used regularly. In this case the hilt is rubbed along the side of the nose (that source of teenage oily skin angst) to coat it.

A somewhat lesser consideration in a martial arts stick finish, is that it bring out the grain of the wood. There is something deeply satisfying about swinging a beautiful thing at someone else's head I think.

So, for our sticks I believe that what we want is good protection from humidity changes, a flexible finish that will move with the wood as it takes its dings and dents, a finish that slides well under the hand (or grips well as the case may be), and one that is easy to reapply and touch up when needed.

Finishes

Let's check out the various types of finish in order of what I think of as light to heavy coverage. All finishes are more or less by definition hydrocarbons and are hydrophobic. They don't mix with water, they are the oils, waxes and resins.

The lightest, least surface protecting finishes are the non-polymerizing oils. This would include nose oil, blood and sweat, mineral oil (baby oil), Lemon, Orange, or Walnut oils, that sort of thing. These all soak into the wood, are fairly short-lived (they tend to evaporate or be wicked out by your hands), and do repel water to some extent. I usually recommend lemon oil to someone who wants to coat their weapons weekly since it won't build up. The oil that doesn't soak into the wood ends up being wiped back off.

Wax would be the next general class of finish, it tends to stay on the surface of the wood (unless it's mixed with oil that carries it into the pores or heated to a liquid state before being applied). It's a good water repellent, and contrary to popular advertising truth, does not form a waxy buildup on our sticks. Wax doesn't stick to wax very well, and once rubbed on it slides off to a thin layer (what does build up is dirt and dust covered in wax I suspect). If it does build up and harden, a bit of orange or lemon oil takes it right off again so it's easy to apply and can be applied fairly often.

I'm not a big fan of wax, myself, I find it a bit sticky and it tends to heat up my hands, something that then promotes sweat and thus swelled, softened skin. This in turn leads to blisters as the loose skin layers tear one from the other.

The next class of finish would be my personal choice, the so-called drying oils, Tung and Boiled Linseed oil. These are liquid oils that polymerize on exposure to air, forming a cross-linked surface that penetrates the wood and is very flexible. Long ago I used Linseed oil but my preference now is a good Tung oil which seems to be somewhat lighter and doesn't have the orange-yellow colour of linseed oil.

A similar sort of finish comes from "finishing oils" like Danish oil or Antique oil. These are oils which contain varnish and thinners, and sometimes Tung oil as well. Many popular tung oil brands contain varnish and I personally avoid these for wooden weapons since the end result is a varnish-like finish rather than an oil finish.

All the oils above will act to highlight the grain of your wood, they soak down more deeply in some areas than others, increasing the differential look of the rings. The surface finishes which we'll talk about now tend not to do this.

Surface finishes are created by using varnish, urethane, lacquer, shellac and similar products. These resins and polymers create a hard coat on and above the surface of the wood and if applied deeply enough can look quite like a plastic case. Many wooden weapons are finished with these products since they are the absolute best for humidity protection and will keep the weapons straight for the longest time. They are also, quite often to my feel, too sticky for use on weapons that slide through the hands. Other folks like them just fine for that very stickiness, and for their low-maintenance qualities.

These then are the general classes of wood finish as they relate to martial arts weaponry. The lighter, more open the finish, the more often you need to maintain and reapply it. The heavier, harder and stiffer the finish, the more mosture resistant, but that very hardness can, in some cases, cause the finish to crack and flake under repeated impact. It's all a matter of personal preference really.

Quick Fixes and Refinishing

There are several quick fixes for your weapons if the finish starts to be a problem. For stickiness due to an over-application of drying oil, you can try using lemon or mineral oil to dissolve and remove the excess oil which won't polymerize fast enough. For stickiness on a varnish or urethane finish you can try washing the stick with soap and water, or use some talcum powder to give it a bit of slide.

Don't be afraid to refinish your weapons. They will benefit from a sanding and re-application of finish whenever they get a bit shaggy. Splinters can sometimes be glued down with white glue if they're not too deep, (in which case they should be retired). Rub the glue against the side of the crack to get it under the wood, then tape the crack closed tightly while the glue dries, remove the tape, sand smooth and re-finish.

If, for example, your weapon is finished with lacquer or varnish and you want to change to tung oil, just sand back to bare wood and apply the tung oil. Be careful with some imported weapons, they may have a stain beneath the lacquer to lighten or blend the wood to a consistant colour. This is a marketing thing and has nothing to do with protecting the wood or improving its qualities, other than its aesthetics. Try not to sand through the stain, or sand it right out... although in some cases that stain may be quite deep.

Storage

It's very important to store your weapons away from sources of heat and to reduce moisture swings if you want the weapons to stay straight. The absolute fastest way that I know to warp a piece of wood is to drop it on a lawn on a sunny summer day. The top will dry in the sun, while the bottom will pick up moisture from the grass. It will curve upward in minutes. If you have a warped stick you might try this, and urethane it as soon as it's straight. Another good way to ruin a stick is to leave it in your car, especially in the back window.

Some folks are quite careful about storing their sticks on the ground rather than leaning up in a corner or on a rack. The bending of wood under a load over time is called creep, and it actually requires a pretty high load and a lot of time. High moisture conditions also contribute to creep. I would suggest that a finished jo or even a bo would not be likely to warp under its own weight in less than several hundred years. On the other hand, if it does warp due to moisture changes within the stick itself, the middle would tend to rotate toward the ground, giving the impression that it had sagged.

So there are some considerations on the care and feeding of your wooden sticks. Use them in good health, keep the finish fresh, sand them once in a while and your weapon ought to give you years of service. When you do notice deep cracks (more than dents and splinters from the dents) or when it looks like the wood is very dry, it's time to retire it to a place of honour and buy a new one. All sticks wear out eventually, just make sure you don't push it too long and send a piece of yours flying across the dojo.

The SDKsupplies formula

Wooden weapons made by SDK Supplies are finished with one coat of "tung and teak" followed by a second coat of tung oil. This allows a finish that penetrates fairly deeply into the wood while not building up on the surface, thus allowing the users to feel the wood directly while protecting it from humidity swings. We recommend refinishing with tung oil but any of the finishes above wil work nicely.

sdksupplies.com

Kim Taylor has been making and finishing wooden weapons for 25 years.

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TIN Aug 2007