Always run a tsuyutoshi or cleaning cloth through the bore of the shakuhachi after playing. Leaving moisture inside the flute allows dust and dirt to build up along the bore and will affect the tone of the instrument. Be very careful when cleaning the bore. Place your thumb over the utaguchi to protect its fine edge, then carefully drop the weight and string into the flute. Pull slowly until the cloth enters the bore without allowing the string to drag against the top or interior wall of the instrument. This may damage the blowing edge or remove paint from the bore. Pull the cloth through, then clean again.