The most important aspects of preserving Japanese swords are to protect them from developing rust and scratches. The precautions required for keeping the sword in good condition are the following: The most important aspects of preserving Japanese swords are to protect them from developing rust and scratches. The precautions required for keeping the sword in good condition are the following:
Store the blade in a Shirasaya
Despite regular care and oiling, a blade may develop rust in places. Especially when a Koshirae is very old, the interior of the Saya may well be contaminated with rust and dirt, thus causing the blade to rust when stored in the Saya. In such a case, a new scabbard must replace the old one at once. If the Koshirae mounting functions as formal wear, a Shirasaya can be thought of as casual wear for a blade. In old times the Shirasaya was also known as “the resting Saya” or the “oiling Saya”. If you are storing your sword in a Koshirae mount, you are recommended to make a Shirasaya for it as soon as possible.
Store the sword in a horizontal position
When storing your sword, put it store it in a horizontal position. When you preserve your sword, it is improper to keep it in a leaning or vertical position because it would cause the oil to go down along the blade surface and make a pool at the tip inside of the Saya. It’s ideal to put the sword in a horizontal sword rack or laid down inside of a box of paulownia wood.
Avoid high humidity
It is ideal to store your sword in a place with low humidity. Although dry conditions are preferable for swords, old Koshirae might also require a bit of moisture to keep the wooden containers or mountings from being damaged. Therefore, the place for preserving swords must be carefully considered and selected with utmost care.
The blade is most vulnerable after being polished
Please pay extra attention to newly made swords or swords that have been polished recently, since a blade is particularly vulnerable to rust within the first 6 months. During this period it might be good to clean and oil your sword more often, preferably no less than once every month. Later when the blade surface condition is more stable, clean it regularly, at least every six months.
Do not attempt to remove rust on your own
If a blade should start to rust, no inexperienced repair such as rubbing the rust off with a spatula will improve the condition; rather it is likely to aggravate it and cause further damage which might greatly affect the value of the sword. If rust is detected, the sword has to be taking to a professional sword polishing craftsman.