It all starts with a small ‘just-plucked’ green tea leaf, usually about 5 cm long, delivered fresh by the picker to the local factory for processing. Whilst varying by region, there are always 5 core steps to making a Black Tea.
Step 1 - ‘Withering’: the leaves are spread out in warm air for up to a day to reduce the water content by about 20%. The leaves wilt and lose some of the vibrant green colour.
Step 2 - ‘Rolling’: the wilted leaves are soft and malleable and are placed in an ‘orthodox’ rolling machine. It presses the leaf and breaks down the cell walls, releasing the enzymes required to start the oxidation process. Sometimes the leaf is broken more by a rotavane ‘mincing’ machine that produces smaller grades of tea. If a very small teabag grade is required, a Cut-Tea-Curl machine is used.
Step 3 - ‘Oxidation’ [not fermentation, which requires a microbe involvement]: takes half an hour or so depending on the conditions. Chemical reactions are now creating the natural chemicals that deliver flavour and [reputed!] health benefits. The leaf darkens, just like a cut apple after a few minutes.
Step 4 - ‘Firing’: the oxidised tea is fed into a dryer at about 120 Celsius. This does 3 things - it destroys the enzymes, so oxidation stops; secondly it removes nearly all the water [about 3% remains]; and thirdly, it darkens the colour from light brown to dark to almost black, depending on the length of firing.
Step 5 - Sorting: tea exits the firing process in different sizes, which will complicate brewing - hence the last stage of the process is grading – fired tea is poured into the top of a sifting machine with different mesh sizes from top to bottom. It vibrates and the different sized tea leaves are separated as the tea travels from top to bottom, the biggest leaves being left the top.