Withering.
Plucking the leaf initiates the withering stage, in which the leaf becomes flaccid and loses water until, from a fresh moisture content of 70 to 80 percent by weight, it arrives at a withered content of 55 to 70 percent, depending upon the type of processing.
In the traditional process, fresh leaf is spread by hand in thin layers onto trays or sections of coarse fabric called tats. It is then allowed to wither for 18 to 20 hours, depending upon several factors that include the temperature and humidity of the air and the size and moisture content of the leaf. Withering in the open air has been replaced by various mechanized systems. In trough withering, air is forced through a thick layer of leaf on a mesh in a trough. In drum withering, rotating, perforated drums are used instead of troughs, and in tunnel withering, leaf is spread on tats carried by mobile trolleys and is subjected to hot-air blasts in a tunnel. Continuous withering machines move the leaf on conveyor belts and subject it to hot air in an enclosed chamber, discharging withered leaf while fresh leaf is simultaneously loaded.
Mechanized systems greatly reduce withering time, but they can also lower the quality of the final product by reducing the time for chemical withering, during which proteins and carbohydrates break down into simpler amino acids and sugars, and the concentration of caffeine and tennon increases. (Sir: is "tennon" supposed to be "tannin" here?)

Rolling.

The object of rolling is to crush the leaves and to break their cells so as to liberate the juices. The leaves are passed repeatedly through a machine driven by steam or other power giving a rotary motion, the operation occupying about 40 to 60 minutes. The next process is familiarly termed fermentation, but is really an oxidation of the leaves. At this stage, the withered leaf is distorted, acquiring the distinctive twist of the finished tea leaf, and leaf cells are burst, resulting in the mixing of enzymes with tannin. (Sir: is "tennon" supposed to be "tannin" here?)

The traditional method is to roll bunches of leaves between the hands, or by hand on a table, until the leaf is twisted, evenly coated with juices, and finally broken into pieces. Lumps of rolled leaf are then broken up and sifted. The smaller leaf passing through the sieve--called the fines--is transferred to the fermentation room, and the remaining coarse leaf is rolled again.

In many countries, rolling the leaf has been abandoned in favor of distortion by a variety of machines.
Fermentation.

Should the leaf be intended to be cured as green tea, the fermenting process is omitted and some other processes applied. After being rolled, the leaves are spread out in layers of I to 2 inches thick in a cool house, and left to undergo the chemical action resulting from their condition. The process actually is not fermentation at all but a series of chemical reactions. The most important is the oxidation of some tannin orange-red compounds called theaflavins, which are responsible for the transformation of the leaf to a dark brown or coppery color. In general, theaflavin is associated with the brightness and brisk taste of brewed tea, while thearubigin is associated with strength and color.
Drying.

Leaves are exposed to hot air up to a temperature of 240° F for about 20 minutes, after which they are firm and crisp. Up to this point of the manufacturing process, the leaf has been in the stalk, the leaves and bud being unseparated. They are now broken apart and sorted by mechanical sifters into the various grades or qualities. Upon completion of the sifting, the tea is again fired, and, while warm it is packed tightly into lead-lined chests, and the lead covers completely soldered over it, so that it may be kept perfectly air tight until required for use.

Traditionally, fermented leaf was dried on large pans or screens over fire, but since the late 19th century, heated forced air has been used. A mechanized drier consists of a large chamber into the bottom of which hot air is blown as the leaf is fed from the top on a series of descending conveyors. The dried leaf is then cooled quickly to prevent overdrying and loss of quality.