The entire process of producing tea can be broken into the following steps: cultivation, pruning, plucking, withering, rolling, oxidization, firing/drying, sorting/grading, and packing. Of these, the first two steps are considered part of the growing process and the last seven steps are considered the manufacturing process.
Withering is the first process carried out within the factory on the plucked tea leaves. The fresh plucked leaves after sorting are placed on the withering troughs and air is allowed to pass over the leaves. The air fans which are used in this process are called 'withering fans'. The process of wither aims at partial removal of moisture from the fresh leaf. It is carried out in order to condition the leaf physically for subsequent processing. Besides, some chemical changes also take place during withering and these are independent of the physical process. The process of withering involves: 1. Physical Wither and 2. Chemical Wither.
After withering the soft tea leaves are put into rolling machines – two large round metal plates that run in different directions and gently twist the leaves thus opening the cell walls of the leaf and allowing the juices inside to get exposed to the oxygen in the air – the start of the oxidation process or fermentation.
It takes a lot of expertise to decide upon the right amount of pressure and the right duration of the rolling process (usually about 20 to 60 minutes) to bring out the best results.
The oxidation process that has been started during withering and rolling reaches its climax during the fermenting process that will last 2 to 5 hours. During this time black tea will develop its characteristic flavour and aroma while losing of its adstringent and bitter taste
The primary objective of drying is the extraction of moisture and the arresting of fermentation. The fermented leaf contains from 45% to 50% moisture. The leaf is passed through driers, which have circuits of trays with perforation, on which are conveyed the fermented leaf.
The drying process takes about 20 to 25 minutes and the initial temperature is about 120 Degrees F(50 Degrees C) and is finished off at a temperature of 200 Degrees F (93 Degrees C) to 220 degrees F (105 Degrees C) . The moisture content of the teas when drying is completed is approximately 2% to 3% and the coppery brown fermented tea particles are now back.
The fired teas after cooling are graded / sifted according to size and shape, as the trade demands. The different grades of tea are identified nomenclature. On completion of the grading, teas are stored in airtight bins of boxes. The sifting is carried out on a series of grading and cleaning machines, which have several trays of different mesh sizes, to separate the tea particles to the various grades of tea and to remove the stalk and fibre.
Teas are very hygroscopic and rapidly absorb moisture. When sufficient quantities of teas are collected, the are either packed in plywood tea chests of multi-walled aluminum craft paper lined pager sacks and despatched to the auctions or packed into tea packs of various forms for direct export/distribution.