Before the first use
Soak the chasen tines down in warm water for one to two minutes before whisking. This softens the bamboo and helps the curled tines open into their natural fan, which makes the first foam easier to build.
After every bowl
Rinse the tines under warm running water and gently swish to release matcha residue. Never use soap, dish detergent, or a dishwasher, since these strip the bamboo and leave residues that can taint flavor.
Drying and storage
Shake off excess water and stand the chasen on a kusenaoshi, a ceramic whisk holder, with the tines facing up. Air drying on a holder keeps the tines from collapsing inward and helps the bamboo dry evenly. With this routine a chasen typically lasts several months of regular use.