Turning the pile (fan dui)
The scheduled turns that redistribute a fermenting heap, which is how a pile is steered — the temperature at its core is the whole control system.
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.
- Dark tea and pu-erh — Post-fermentation: microbial wet-piling (shou) or extended natural ageing (sheng).
What it is
A wet-piling heap is not left alone. Microbial activity generates heat, the core of the pile climbs well above the room, and if it is allowed to keep climbing the population inside shifts and the leaf carbonises at the centre while the outside stays raw. So the pile is turned on a schedule — every few days, more often early — by shovelling the whole mass over so that outside becomes inside, breaking up the compacted clumps, and re-heaping and re-covering it. Each turn drops the core temperature, admits oxygen, and evens out both moisture and microbial population across the mass. A fermentation manager judges the schedule by putting a hand or a probe into the core, and the record of turns is essentially the record of the batch. At the end the heap is opened out and spread to dry, which halts the process; the same operation, performed for the opposite reason.
Also transliterated as: fan dui, fandui, kai dui.
What it does to the leaf
Redistributes a fermenting mass to lower its core temperature, admit oxygen, break compaction and even out moisture and microbial population between the interior and the surface.
What it does to the cup
Frequent turning gives a cleaner, lighter, more even shou; a pile turned too seldom develops a burnt or sour core, and one turned too often never reaches the temperature at which conversion happens at all.
Variants that matter
Ways this step is carried out that produce genuinely different results, rather than regional names for the same thing.
- Early frequent turns
- Turns are closest together in the first fortnight, when heat generation is fastest and the risk of running away is highest.
- Opening the pile (kai dui)
- The final turn, in which the heap is spread out rather than re-covered, so it cools and dries and the fermentation stops.
- Basket and small-batch fermentation
- Turning between baskets rather than shovelling a floor heap. Slower, more controllable, and now used for high-value shou where a large pile's variability is unacceptable.
Where this gets misdescribed
The length of a fermentation is quoted as though it were the specification — forty-five days, sixty days. What varies between a good pile and a bad one is not the calendar but the turning schedule and the core temperature it held, and two piles run for the same number of days can produce teas with nothing in common.
Other steps at the Fermentation stage
- Anaerobic pickling — Packing steamed leaf into a sealed vessel and excluding air, so lactic acid bacteria rather than moulds carry out the fermentation.
- Fungal flowering (jin hua) — Deliberately cultivating Eurotium cristatum on compressed dark tea until visible golden spores develop.
- Liu Bao pile fermentation — Wuzhou’s own microbial piling process for Liu Bao, which shares a family with pu-erh wet-piling and is not the same operation.
- Wet piling (wo dui) — Deliberate microbial fermentation of finished leaf under heat and humidity — what makes shou pu-erh.
- Wetting the pile (chao shui) — The measured addition of water to dry maocha that starts a wet-piling fermentation, and the single decision that most determines what the finished shou tastes like.
Guides covering this step
- The steps between the steps — Spreading, cooling, resting, turning. Four operations that occupy most of the elapsed time in tea manufacture, have names in every producing language, and are compressed in English writing into the word “then”.
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.