Cleaning World War II Gunto
Rust and Substance Removal for WWII Bar-Stock Blades

by WarAngel and Motoyasu

There was probably no other period in time where the West received a tremendous influx of Japanese swords other than at the end of World War II. Many G.I.s brought Japanese military gunto swords over as wartime trophies. Many of these were in superb condition those decades ago, but today, many are extremely damaged by lack of care, or careless handling or regard for these swords.

As pre-World War II swords and ancient era swords are very expensive, many starting-out collectors find the World War II era swords desirable and affordable. Some may collect them to restore them. Others restore them as martial arts practice weapons.

This article deals with how to clean some of those swords which are covered with all kinds of rust and substances, and examines both correct and incorrect methods of cleaning.

Pre-Flight Check

There are various ways to clean blades, some correct, some incorrect. Before proceeding, make absolutely sure you research the background on your blade and compare it against this criteria:

1. Is it an antique/historical blade?
2. Is it a traditionally made blade?
3. Is the sword made from bar-stock or by forge-folding?

Any incorrect cleaning proceedures can result not only in the damaging of the sword but also greatly decreasing its intrinsic value. This is especially true of antique Japanese swords (those that are forge-folded blades, and those that are pre-World War II). The reason why is that the valuation of antique Japanese swords is based on tang rust, blade condition, etc. and any improper tampering of the sword by non-professional methods can cause ruination to a sword, and a historical blade would be lost to future generations. Thus consult a properly trained Japanese Sword Polisher, often known as a Togishi.

Traditionally made forge folded blades are far more valuable than the factory-churned bar stock-ground blades. It is not advisable to proceed with the cleaning tips in this particular article if the sword is forge-folded!

The Wrong Ways

Someone once said that if we do not learn from history, we are bound to repeat its mistakes! These are quite a few mistakes those of us in the West have made. The results are very unfortunate, and many damaged swords end up at Gun Shows. Because most military gunto are mass produced, they are not worth the effort of a traditional restorative polish that can cost you as much as or many times the value of the sword itself.

Coating - Many G.I.s coated their blades with Cosmoline, which is essentially the same petroleum gelly as Vaseline, except for many other additive chemicals. Unfortunately, these chemicals may stain the blade steel or trap moisture or other elements that can cause corrosion. For blade preservation, a non-corrosive oil that adds no other protective agents such as Teflon or silicone, etc. is ideal. Remmington Gun Oil or Ballistol are probably a good way to go, if traditional Japanese choji clove oil is unavailable.

Sharpening - Many Americans tried their hand at sharpening their Japanese swords at a belt grinder or benchtop stone grinder, by creating a 2-3 millimeter bevel on the edge of the swords. Japanese swords have a convex cross sectional geometry that we know today as a Moran edge.

The convex edge on Japanese blades gives them a good balance between edge sharpness and edge toughness- both of which are needed for optimal cutting. Combined with the very hard edge on the sword, with the proper sword techniques, you might not need sharpening for a lifetime. However, this optimal geometry is destroyed by adding a beveled edge - thus "Americanizing" a traditionally shaped Japanese sword. Another problem with grinders is that they can generate such high temperatures that the temper on the edge of a Japanese sword is affected, such that you're now removing the differential temper and causing the edge to go from hard to soft.

Rust Removal - Traditional Japanese swords are constantly kept clean and maintained, so that they look in the same condition as the day they were made. Naturally, unprotected swords exposed to the elements are prone to rusting. Rust removal with traditionally-made Japanese swords should be done by a trained Japanese sword polisher. The problem with many swords today is that some Americans have unwittingly committed their blades to a belt grinder or a high speed buffer to "polish" them. They may not only destroy the temper (hardened edge, softer body) but they place a bazillion deep scratch marks into the blade. Now instead of the sword being worth, say, US$800, it may not be worth the price of the fittings.

The Right Ways

Make sure you've satisified the aforementioned criteria before proceeding. Since mass-produced gunto have far less intrinsic value than the more rare hand-forged gunto, and, consequently, antique pre-World War II swords, there is less loss of value in working on a factory-produced sword. Thus verifying that your sword is not a forge-folded piece is paramount. Sometimes it's hard to tell especially if there is a tremendous amount of rusting or old substances coating the blade.

If there is tremendous rusting and other various substances (possibly Cosmoline) on the blade, try rubbing the sword down with mineral spirits and/or acetone. This will remove anything that is soluble such as old cosmoline or old dried oil, etc. If there is rust on the blade, get a big tub and fill it with kerosene or WD40 and let it soak for a week or so, and then scrub the blade under the oil with a brass/bronze wire brush. This shouldn't scratch the steel, but it should remove whatever removable rust there is. (You can also use bronze wool afterwards to get any leftover deposits.)

What you should end up with is a clean but blemished blade. At this point, you should make a determination as to whether the blade is a traditionally folded blade or a simple bar-stock blade. If it's traditionally made, send it to a polisher. If it is an unfolded factory steel blade, you can consider doing a bit of cleanup using grades of sandpaper on a hard backing or whetstones to slowly grind away the imperfections and bring the blade to a smooth finish. If there are pits in any area of the blade, it is important not to concentrate on the pits but to grind the whole length of the blade to reduce the shape evenly. If you don't do this and just sand over top of the pits, you'll wear this part of the sword more than the rest and end up with an unsightly dip in the surface. The same goes for chips or any other imperfection - ignore it as if it wasn't there and polish the entire length.

When you've brought the blade up through a number of increasingly fine abrasives and the blade is clean and well shaped, one of many different methods may be used to bring out the temper line (if any; many gunto were fully oil-quenched without clay and have no temper line). Modern bladesmiths often use an etch of Ferric Chloride or dilute Nitric Acid followed by a very fine abrasive metal polish to bring out the hamon. If you'd prefer not to bother with chemicals, you may also use 2000 grit or better silicon carbide paper with oil as a lubricant, which will put a similar matte finish on the blade and expose the hamon. For the most authentic finish, you can purchase Japanese hazuya and jizuya finger stones and nugui compound. The stones are ground on a coarse whetstone until they are paper-thin and then they are rubbed on the sword using water as a lubricant until the surface is scratch-free and an even matte appearance. The nugui compound is then crushed to a fine powder and mixed with oil and rubbed onto the blade with a cotton ball until the appearance of the blade is as you desire (the nugui will also improve the appearance of all the previous non-traditional methods).

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