Aperture governs aroma delivery
A narrow opening holds volatile aroma above the liquid and concentrates it as you bring the cup up; a wide bowl lets it disperse. This is why the tall narrow aroma cup used in Taiwanese practice works at all, and why a wide open bowl is used where the tea is meant to be drunk warm and quickly rather than smelled. The effect is real and it is also the least interesting kind of real: it changes how much aroma reaches your nose in the moment, not what is in the tea.
Surface area governs cooling
A wide shallow vessel loses heat fast, a tall narrow one slowly. That single fact explains why a matcha bowl is drunk promptly and why a yunomi keeps tea hot at a desk, and it explains why the same tea served in two different cups can genuinely taste different — because it is at a different temperature, and temperature changes what a palate reports. This is the mechanism behind a great many claims about cup shape and flavour, and it is worth naming because it is testable and the alternatives are not.
The rim, which is the part you actually touch
A thin rim delivers liquid to a narrow band of the lip and feels sharp and precise; a thick rounded rim spreads it and feels soft. A flared rim is much easier to hold when the cup is full and hot, which is why handleless cups so often have one. Rim thickness is the feature drinkers most consistently notice and least often name, and it is one of the very few teaware properties where a preference can be tested directly: pour the same tea into two cups and swap between them.
Interior colour, and reading the liquor
A white or pale interior lets you judge liquor colour and clarity; a dark one does not. That is the whole argument, and it is why professional tasting uses white porcelain. It cuts the other way for whisked matcha, where a dark bowl shows pale foam better. Neither is about flavour and both are about being able to see what you have made.
What is claimed and cannot be supported
That a particular cup shape makes a tea sweeter, that a specific rim curve directs liquid to a region of the tongue that perceives sweetness, that certain proportions bring out qi. The tongue-map claim in particular is repeated in tea and wine writing and is not how taste perception works. TeaHQ’s position is that aperture, surface area, rim geometry and interior colour are real and largely account for what people notice, and that claims which go beyond them are unsupported by anything it can source.