What is Uchiko in Japanese Katana terminology?
"打粉" or "Uchiko" is a tool used to remove old clove oil (丁子油 or Chōjiyu) for the purpose of appreciation. It contains a powder of Uchigumori whetstone (内曇砥石 or Uchi gumori toishi) in a silk cloth, which is applied to the blade of the sword. By doing this, the powder is applied to the blade. This powder is then wiped off, which removes the oil from the blade.