Caring for Your Japanese Sword — Proper Maintenance to Preserve a Masterpiece

Why Maintenance of Japanese Swords Is Essential

Japanese swords are precision iron products forged from carbon steel. If proper maintenance is neglected, moisture and oxygen in the air react to cause oxidative corrosion (rust), and the beauty of the hamon and jigane is lost in just a few months. Even swords designated as National Treasures or Important Cultural Properties have maintained their brilliance to this day only through the meticulous maintenance passed down by successive caretakers. To love a fine sword for a long time and pass it on to the next generation, regular and accurate maintenance is absolutely essential. Generally, maintenance once a month is considered the standard, but adjustments are needed depending on storage conditions and season. During the rainy season and high-humidity summer months, increase the frequency, and during winter's dry season, when oil evaporates quickly, increase the frequency of checks.

Tools Required for Maintenance and Their Roles

Proper maintenance requires specialized tools. Understanding each tool's role accurately prevents damage to the blade from improper maintenance. Uchiko is a polishing powder made by molding clove oil into a sphere, and its role is to adsorb and remove old oil residue and fine dirt remaining on the sword blade surface. Choji oil is a rust-preventive oil specially designed for Japanese swords, with clove essential oil as its main component, and is applied thinly as a protective film on the blade. Wipe paper (nugu-igami) is soft Japanese paper such as fine-fibered Hosho paper, used to wipe away oil and uchiko without damaging the blade. A mekugi puller is a specialized tool for driving out the mekugi that secures the tsuka and nakago. If you have a katana stand, you can keep the sword in a stable position during maintenance. These tools are available as maintenance sets from Japanese sword specialty shops and mail order.

Proper Maintenance Procedure

Before starting, secure a stable, wide work surface to prevent the sword from rolling and falling. First, gently tap the mekugi with a mekugi puller to remove it, then carefully pull out the tsuka to expose the blade. Touching the blade directly with your hands is strictly forbidden. The oils from your fingertips can cause rust. Wearing white gloves is strongly recommended during work. First, use dry wipe paper to carefully remove old oil from the blade. The wiping direction must always be from the spine side (munegawa) toward the edge side (hagawa), as wiping in the reverse direction risks creating scratches. Next, lightly apply uchiko to all parts of the blade to adsorb the oils, then completely wipe away the uchiko with fresh wipe paper. The trick is to apply the uchiko lightly with gentle taps, not by pressing hard. Finally, take a small amount of choji oil on wipe paper and apply it very thinly and uniformly over the entire blade. Since excess oil invites rust, after application, lightly wipe with another piece of paper to create a uniform thin film.

Storage Environment and Storage Precautions

After maintenance, carefully place the blade into the shirasaya. The shirasaya is a plain wooden storage sheath that protects the blade from impact while allowing the wood to absorb and release moisture appropriately, stabilizing the blade's environment. The ideal storage location completely avoids direct sunlight, has minimal temperature fluctuations, and maintains humidity between 40-60%. A shelf in a closet or a dedicated tou-bako (sword box) is suitable. When storing horizontally, positioning the blade with the edge facing up minimizes blade movement within the sheath and prevents scratches. The volatile components of moth repellents can negatively affect metal and lacquer, so their use inside the sword box should be avoided. Make it a habit to remove the sword at least once every three months to check its condition and verify that no new rust has developed and there is no moisture inside the sheath.

Requesting Work from a Polisher and Restoration

Over many years of repeated maintenance, the cumulative effect of uchiko polishing gradually makes the blade thinner. Additionally, if rust progresses or damage occurs, there are limits to what an individual can do. In such cases, the best course of action is to consult a professional togishi (sword polisher). The togishi is not only a person who polishes the edge with a whetstone, but also an artist who brings out the hamon and jigane's original character. It is not uncommon for re-polishing to bring a dulled hamon back into sharp relief and revive the jigane's texture. Choose your togishi carefully, and if possible, obtain a referral from a reputable sword dealer or sword preservation organization. Polishing fees vary depending on the blade length and condition, but should be viewed as a necessary investment to maintain the sword's value.

Mindset of the Sword Owner

Maintaining a Japanese sword is not merely maintaining a metal object. It is an act of showing respect for the skill and spirit of the swordsmith who created the sword, the history of the samurai and daimyo who wielded it, and the dedication of the people who have passed it down through generations. By spending time carefully on monthly maintenance, you develop a dialogue with the sword and deepen your understanding of its subtle beauty. By continuing proper maintenance, the sword in your hands will shine for centuries to come and be passed on to future generations. Owning a sword means becoming a temporary custodian of a cultural treasure. This responsibility demands that you be consciously engaged and take your daily maintenance seriously.

Common Mistakes and Precautions

Here are some typical mistakes that beginners commonly make during maintenance. The first is applying uchiko too vigorously by rubbing. Uchiko should only be lightly applied to the blade; rubbing with pressure creates fine scratches on the jigane surface and damages the finish. The second is applying too much choji oil. A thick coat of oil actually attracts dust and causes rust. Apply thinly and uniformly, and always wipe away excess oil. The third is touching the blade with bare hands without white gloves. The oils from your fingertips are a strong rust trigger, so always wear gloves while working. The fourth is using metal tools (such as tweezers) on the blade. This creates fine scratches that require a togishi to repair. By knowing these precautions in advance, you can greatly reduce the risk of carelessly damaging your precious sword. If you are uncertain about maintenance, it is also effective to attend demonstration workshops held by sword dealers or preservation organizations to learn the actual procedures.