A traditional Japanese sword isn't complete just because the blade has been forged, the metal cooled and the mud removed. Polishing is a critical step in finalizing a sword. To learn more about polishing Japanese swords and how it's done, keep reading.
#1) There's a Specialist Who Polishes Swords
It's not the swordsmith who polishes the swords. Instead, there's a specialist known as a togishi who's responsible for this task. In the old days, the togishi traditionally used three types of stone to polish a sword. Today, however, togishis use more than a half dozen.
#2) Polishing Takes Time... Lots of Time
You might assume that polishing a Japanese sword is a quick and easy process, requiring just a few minutes to complete. However, this couldn't be further from the truth. In most cases, polishing takes longer than actually forging the blade, with a typical polishing job taking about 2 to 3 weeks. It's a time-consuming and methodical process, which is why there's a specialist who's given this task.
#3) Poor Polishing can Ruin the Blade
Polishing the sword helps to improve the blade's clarity and aesthetics. However, a bad polish can have some serious effects on the sword, potentially even damaging or ruining it. If the togishi alters the blade's geometry and/or wears down the steel too much, it can destroy the sword's function and value.
One of the processes in polishing a traditional Japanese sword is glazing, which involves the use of fine-grain polishing stones to achieve a mirror finish on the cutting edge. For the blunt edge of the sword, however, the togishi strives for a matte finish to make the hamon more visible and appealing.
#5) Polishing Provides 'Insight' into the Sword's Production
A well-polished Japanese sword can reveal a variety of information about the way in which it was produced. For instance, it reveals how fast (or slow) the cutting edge was cooled; at what temperature the blade was cooled; and even the carbon content of the steel itself. Of course, these findings are only visible in well-polished blades. If the blade was not polished or poorly polished, you can't identify these characteristics.
#6) All Polish Must Be Removed
One the sword has been fully polished, the togishi must remove any trade amounts of the oil. Even small amounts can harm the blade by promoting rust and corrosion. Salts within the polishing oil provide ideal breeding grounds for mold and mildew, which can in turn lead to corrosion.