The process of buffing and several times of varnishing and polishing is called "Koba-nuri（コバ塗り）" in Japanese and usually adopt in luxury men’s bag. Since this process needs hand work, the number of parts that can be finished in a day is limited. But the amount of time and effort can finish a more beautiful and elegant edge coating.
For beautiful edge coating, the flap needs to be slowly passed through the rotating machine while ensuring the correct speed and pressure are applied. It's a delicate process where any inconsistency in speed or pressure can result in uneven varnishing.
