Upcountry tea factory withering lofts: airflow hygrometry and moisture loss during night mists?

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David Planter935 rep

How do night-shift teamakers in Nuwara Eliya balance reversible axial fan airflow to reduce green leaf moisture from 75% to 55% during freezing montane mists?

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Accepted Answer

Withering is the foundational physical and chemical stage in orthodox black tea manufacture, conducted overnight in long elevated troughs. Harvested green leaves holding 75% moisture must reach 52-55% moisture over 14 to 16 hours. During freezing night mists in Nuwara Eliya when ambient relative humidity reaches 98%, dry-bulb and wet-bulb temperatures converge. Teamakers mix radiator heat from firewood boilers with ambient loft air to maintain a functional 3°C wet-bulb depression, reversing axial fan airflow every three hours to ensure uniform leaf withering without case-hardening.

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Dr Senaka Tea1810 rep

Under-withering produces watery, bitter tea liquors with flaky broken leaves, while over-withering concentrates polyphenols too quickly and stalls enzymatic fermentation.

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David Planter935 rep

The characteristic sweet fragrance of ripe apples given off in the withering loft indicates optimal breakdown of amino acids and chlorophyll.

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Toby Semaphore895 rep

Troughs are loaded at a standardized density of 1.5kg of green leaf per square foot of nylon mesh to allow air currents to penetrate leaf beds evenly.

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Nils Regosol890 rep

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