After each use
Reprocessed tea leaves the widest range of residue on the site, since it covers three product types.
Scented jasmine leaves an oily film, and that film is the one that turns rancid if it is left.
Empty the leaf within 5 minutes and rinse with hot water while the vessel is still warm.
Wipe the inside with a cloth kept for the purpose, and wipe it dry rather than wet.
No detergent on anything porous, and as little as possible on glazed ware.
A scented tea picks up a residue faster than you can taste it, which is why it matters here.
Compressed pu-erh leaves the same brown film as it does in the dark tea category.
Gan pu（柑普）leaves citrus oil, which is stickier than either and needs hot water rather than cold.
Cold water moves oil around, and hot water takes it off the surface.
Turn the vessel upside down on a rack and let it dry in open air with the lid off.
A gaiwan of 100 ml dries in about 1 hour, and a tall glass takes less than that.
Two minutes after each session, and none of the residues in this category ever build up.
Dedication versus neutrality
Dedication is required for clay and impossible for anything else, and this category uses both.
Scented tea and clay do not mix, because the pot takes up the flower aroma and keeps it for months.
A jasmine pot will make every later tea taste faintly of flowers, which is rarely what anyone wants.
Compressed pu-erh and clay do mix, and that is the same arrangement as in the dark tea category.
A zisha（紫砂）pot dedicated to ripe pu-erh improves over about a year of regular use.
So one clay pot can serve half the category and must be kept away from the other half.
Two pots would solve it, and two pots is more commitment than most drinkers need.
Porcelain and glass stay neutral and cover all three product types without any argument.
Brew jasmine at 90 °C in the morning and a compressed cake at boiling in the evening.
Rinse between the two and nothing carries over, because there are no pores to hold it.
Start neutral, stay neutral until you know which half you drink most, and only then consider clay.
The decision is permanent, so there is no reason to take it early.
What to avoid
Avoid detergent on clay, since the pores hold it and release it into the tea for weeks.
Avoid the dishwasher, which is too hot for thick clay and too strong for anything glazed.
Avoid abrasive pads on glazed ware, because a scratched surface starts remembering what you brew.
Avoid leaving scented leaf in the vessel overnight, which is the fastest way to a rancid smell.
Jasmine leaf left for 12 hours turns sour, and the oil in it goes rancid at the same time.
Avoid putting ware away damp, since a warm kitchen and a closed cupboard grow mould.
Avoid storing a gan pu vessel with the lid on, because citrus oil and trapped moisture are a bad pair.
Avoid one cloth shared with the kitchen, since it carries the smell of whatever it dried last.
Avoid stacking wet pieces, because the moisture trapped between them cannot escape.
Avoid a stiff brush on a seasoned pot, which scratches the surface doing the work.
A rinse of 10 seconds with hot water after every session prevents nearly all of these.
Rancid oil is the particular risk in this category, and dry air prevents that too.
Long-term
Over years, a porcelain gaiwan stains brown and a glass one clouds slightly, and neither matters.
The stain is tannin, it is harmless, and scrubbing it out means scratching the surface.
If you want it gone, a paste of bicarbonate of soda and water left for 30 minutes lifts it.
That works on glazed surfaces and must never go near unglazed clay.
A seasoned clay pot should be rinsed in hot water and dried, and never scrubbed.
Check glazed ware for craze lines once or twice a year, and retire anything cracked.
Check the lid on a gaiwan, since a loose one costs you aroma on every single infusion.
Aroma is the product with a scented tea, and a badly fitting lid throws it away.
Check the spout as well, because a dribbling vessel loses aroma while you fumble with it.
Replace cheap ware freely rather than repairing it, since a plain gaiwan costs very little.
A vessel used daily for 3 years has taught you more than a new one will for a long time.
Clean it, dry it, replace it when it fails, and that is the whole routine.