The same equipment, doing different jobs
A woven basket over a low charcoal fire dries a green tea. Run hotter and longer, the same basket is the roasting basket used for oolong. A heated pan fixes a green tea and, at the end of the same route, finishes it. A hot-air machine dries an aracha and, at a different setting in a different building, fires it to a style. This is why the vocabulary of drying and roasting overlaps as much in Chinese as it does in English: the operations genuinely share equipment, and the distinction between them is not in the machine. It is in what is being done and when. That makes position in the sequence the reliable discriminator, and the words unreliable ones.
Fixation: heat that destroys enzymes
The first heat in any route that has one. Its purpose is to denature the enzymes that would otherwise brown the leaf, and it does that in minutes. Everything about it is arranged around speed and completeness: it has to reach all of the leaf, and it has to reach it fast, because a batch fixed unevenly contains material that is still changing alongside material that has stopped. The toasted note that pan-firing contributes is a by-product rather than the goal, which is why describing pan-firing as roasting the tea is wrong in a way that matters — roasting is a separate, later, much longer operation applied to a tea that is otherwise finished. If the heat comes before any oxidation was permitted, it is a fixation.
Drying: heat that makes the tea keep
The heat that takes a tea to storage dryness, and in an oxidised tea it does a second job first — the first seconds in the drier are what stop the oxidation, so the drier is also the arresting step. Drying is staged rather than continuous for a physical reason: surface moisture leaves fast and internal moisture has to diffuse outward first, so a single hot pass produces a dry shell around a damp core. The correct construction is a hot fast first pass, a rest, and a cooler longer second one. Drying is also where a route's whole future is decided, because there is one substitution available at this slot with enormous consequences: an oven finishes the leaf and the sun does not. A sun-dried maocha still carries residual capacity to change, and that is the entire basis of the pu-erh family.
Roasting and firing: heat applied to a finished tea
Everything after the tea is otherwise complete. Roasting a strip oolong over charcoal runs for hours at a heat low enough to caramelise rather than toast, and is repeated across months with long rests between rounds; its purpose is to build sweetness and depth and to set a style. The Japanese finishing fire does something narrower — it takes refined tea to storage moisture while the refiner chooses how much browning to develop — and pushed far enough it stops producing a green tea and produces hojicha. Re-firing is smaller again: a light refresh applied to a stored tea that has taken up moisture, which resets it rather than developing it. The common property is that all of them act on a tea that could have been sold as it was, and the distinguishing property is duration and intent.
How to tell which one a description means
Ask where it sits. Heat before any rupture or any oxidation is a fixation. Heat immediately after oxidation, or as the last step of manufacture, is a drying. Heat applied to a tea that is already dry and already saleable is a roast or a firing, and the difference between those two is mostly how long it runs and whether it is repeated. A description that says a tea was fired usually means the last of these and occasionally means the first, and the only way to be sure is the position. This is also why a temperature figure on its own is uninformative: the same temperature is a fixation at three minutes, a drying at twenty and a roast at four hours, and none of the three is doing the same thing to the leaf.