Drum fixation
Kill-green in a heated rotating cylinder that leaf passes through continuously, which is how most Chinese green tea is now fixed.
The categories this step defines
In tea, processing is not a modifier applied to a category — it is what creates the category. These are the types that exist because this step exists.
- Green tea — Kill-green (fixation) applied before meaningful oxidation can develop.
What it is
A fixation drum is an inclined heated cylinder, sometimes several metres long, into which fresh leaf is fed at one end and out of which fixed leaf falls at the other. Internal flights lift and tumble the leaf so it meets the hot wall repeatedly rather than resting against it, and residence time is set by the drum’s angle and speed. Against a wok it gives up the maker’s continuous judgement and gains something a wok cannot: a genuinely constant temperature and an identical treatment for every kilogram in a day’s intake. Nearly all volume Chinese green tea, most Korean green tea and a good deal of what is sold as hand-made passes through one, and the honest description of a modern premium green tea is often that the drum did the fixing and the hands did the shaping.
Also transliterated as: gun tong sha qing, guntong shaqing.
What it does to the leaf
Passes leaf continuously through a heated rotating cylinder, denaturing oxidation enzymes by repeated brief contact with hot metal and hot air rather than by resting on a pan surface.
What it does to the cup
Cleaner and less toasted than wok firing, with less of the chestnut note that comes from leaf pressed against a hot surface, and markedly more consistent batch to batch.
Variants that matter
Ways this step is carried out that produce genuinely different results, rather than regional names for the same thing.
- Hot-air assisted drums
- A stream of heated air is drawn through the drum alongside the wall heat, which shortens the pass and reduces scorching on the tumbling leaf.
- Steam-then-drum
- A short steam ahead of the drum, used where the intake is very wet. It fixes fast and then finishes in the drum, borrowing from both traditions.
- Microwave and radio-frequency fixation
- Heats the leaf from within rather than the surface inward. Real, in commercial use, and still a minority method whose effect on aroma is disputed within the industry.
Where this gets misdescribed
Machine fixation is treated as a shortcut that a traditional producer would avoid. In practice the drum is more forgiving of the thing that actually ruins green tea — uneven fixing, which leaves some leaf oxidising in a batch that is supposed to have stopped — and many highly regarded producers use a drum for fixation precisely so they can spend their attention on the shaping that follows.
Other steps at the Fixation stage
- Kill-green (fixation) — Heating the leaf to stop oxidation — the step that makes green tea green.
- Pan-firing (Chinese fixation) — Fixation by direct contact with a heated wok or drum, which halts oxidation and toasts the leaf at the same time.
- Spreading and cooling (tan liang) — Getting the heat out of the leaf immediately after a hot step, because heat that stays in the leaf keeps cooking it after the operator has stopped.
- Steaming (Japanese fixation) — Fixation by live steam rather than dry heat — the choice that separates Japanese green tea from Chinese.
Teas that go through this step
Guides covering this step
- Why green tea is the hardest category to make well — Green tea has the fewest steps and the least margin. There is nothing in the process that hides a mistake, no oxidation to build over a weak start and no roast to cover a flat finish, and every error is still in the cup at the end.
- Steam or pan: the fork that split green tea in two — Japanese and Chinese green teas taste categorically different, and the reason is not the plant, the place or the picking. It is that one tradition stops oxidation with steam and the other stops it with hot metal.
Sources
- TeaHQ editorial synthesis — TeaHQ
This page is TeaHQ’s own synthesis of well-attested production practice. No external technical document stands behind it, so it describes what producers do rather than asserting measured process parameters.
Written comparisons
Where TeaHQ has set this step against something it is routinely confused with, and argued the differences out in full.
- Drum fixation vs pan-firing — Almost all Chinese green tea is now fixed in a heated rotating cylinder rather than in a wok, and the two are usually described interchangeably as pan-firing. The heat transfer is different, and so is what the leaf can be made to do while it is being fixed.