After each use
Green tea brews at 80 to 85 °C and leaves very little behind, so the cleaning is quick.
Empty the leaf within 5 minutes of the last pour, since dry leaf stuck to porcelain takes scraping.
Rinse the vessel with hot water and wipe the inside with a soft cloth or brush.
No detergent on anything you brew in, because a scent left in the vessel ends up in the tea.
A residue you can smell is a residue you will taste, and detergent residue is easy to smell.
Turn the vessel upside down on a rack and let it dry completely before you put it away.
Drying matters more than washing, since a vessel put away damp grows mould in a warm kitchen.
Leave the lid off or propped open, because a closed damp gaiwan stays damp for days.
A gaiwan（盖碗）dries in about 1 hour in open air and takes a day with the lid on.
Wipe the outside as well, since tea stains build up slowly and are harder to remove later.
A stain is not dirt and it is not a fault, but it does hide the colour of the liquor.
Two minutes after each session is enough, and nothing more is needed.
Dedication versus neutrality
The question every buyer faces is whether to dedicate a vessel to one tea or keep it neutral.
Porcelain and glass stay neutral no matter how you treat them, as long as the glaze is intact.
You can brew green tea in the morning and ripe pu-erh in the evening in the same gaiwan.
Rinse it between the two and nothing carries over, because there are no pores to hold anything.
Unglazed clay is the opposite, and it becomes a record of everything brewed in it.
A clay pot used on green tea will gradually smell of green tea, and then of whatever replaced it.
Dedication is the answer for clay, and there is no version of clay where it is not.
Keeping a pot neutral means never letting it absorb anything, which means never using it.
For green tea the choice is easy, since the category is better off in a neutral vessel anyway.
Clay adds nothing to a delicate leaf and takes away the temperature control you need.
So a green tea drinker can skip the whole argument and use porcelain for everything.
Dedication only becomes a real decision once you take up dark tea or roasted oolong.
What to avoid
Avoid detergent first, and that includes the small amount people use on a stubborn stain.
Anything scented leaves something behind in a porous surface, and even glazed ware holds a film.
Avoid the dishwasher, since the detergent is stronger and the heat higher than any tea needs.
Avoid abrasive pads on glazed porcelain, because a scratched glaze stops being neutral.
Once the surface is scratched, liquid gets into the body and the vessel starts to remember things.
Avoid leaving leaf in the vessel overnight, which is the most common mistake by a wide margin.
Wet leaf sitting for 12 hours turns sour, and the smell goes into anything porous.
Avoid stacking wet pieces, since the trapped moisture does the same thing more slowly.
Avoid storing ware in a closed cupboard while it is still damp, which is how mould starts.
Avoid a cloth you also use for something else, because it carries whatever it last dried.
Keep one cloth for tea ware, or rinse the vessel and let it air dry instead.
A rinse of 10 seconds with hot water is enough after most sessions, and that is the whole routine.
Long-term
Over years, porcelain and glass change very little, and that is the point of using them.
Expect stains on the inside and a few chips on the rim, and treat both as normal wear.
A chip on the rim is a reason to replace a gaiwan, since a chipped lid seals badly.
A badly sealing lid spills boiling water, and that is a burn rather than an inconvenience.
Stains can be lifted with a paste of bicarbonate of soda and water, left for 30 minutes.
That works on glazed surfaces and on glass, and it is the only cleaner worth keeping.
Check craze lines once or twice a year, since a cracked glaze stops being neutral.
A crazed vessel behaves like clay from then on, and should be retired from comparison tasting.
Replace cheap ware freely rather than repairing it, because a plain gaiwan costs very little.
A vessel you have used daily for 3 years has taught you more than a new one ever will.
That is the only thing worth preserving, and it lives in your hands rather than in the pot.
Clean it, dry it, replace it when it chips, and the routine never gets more complicated.