The train of diffrent processes that fresh plucked leaf undergoes is
designed in the first place to prepare the leaf for fermentation; in
the second to establish teh best conditions for its action and finally
to aresst the process when it has gone far enough.

The care and attention needed to ensure satisfactory manufacture
should start in the field. The treatment of the leaf from the moment
of detachment from the bush to that place where manufacturing begins
is also of equal importance. The fermentation process begins
immediately a leaf is bruised. If this occurs in the pluckers hand, or
in the containers in which the leaf is transported to the factory,
such fermentation is uncontrolled. Careful handling of plucked leaf
and avoidance of tight packing in bags, baskets or other containers
are of the essence of good manufacturing technique.

WITHERING.

In systems of traditional manufacture the first stage in the
processing of tea is withering. Normally this is carried out by
spreading the tea leaves, thinly on banks of trays or "tats" made of
tightly stretched jute hessian or wire netting. Ten to fifteen squre
feet per pound of fresh leaf is a normal density of spread. The tats
are spaced five to six inches apart, to allow free access of air, with
alley-ways between each bank to allow distribution and removal of
leaf.

Light withers (40 to 42 per cent out turn) are usual in Assam and East
Africa, and medium to hard withers (45 to 50 per cent out turn) are
normal in ceylon. The average lenghth of time for withering is
eighteen to twenty hours where tats are used. There is much
flexibility in these figures depending from factory to factory.

The prime objective of withering is to prepare the leaf for rolling by
making the leaf tissues flaccid and permeable to the juices which the
rolling will wring out and spread evenly upon the surface.

Insufficent attention to withering standards leads to many
complications later.

In the subsequent stage of rolling it is difficult to keep under-
withered leaf from being thrown out of the machine, and in extreme
instances the juices may be expressed and lost. When unduly wet the
macerated leaf clogs the sieves of the sifiting machine. Most serious
of all, to light a wither will overtax the drier inthe firing process.
Under-withered leaf also tends to produce flaky tea of low apparent
specific gravity.

Long withers have a favourable on colour in the brewed tea but this is
secured on the expense of quality. Where long withers are the result
of too slow a removal of surface moisture , in this there is a risk of
the rapid proliferation of ubiquitous and unwanted bacteria which
produces dull and characterless tea.

ROLLING

When a satisfactory wither has been obtained the leaf is ready for
rolling, which twists the leaf, breaks it up and expresses the juices.
The machines used vary in size and design but their principles are
alike: they compress and turn the leaf over, keeping it in continula
motion, in a manner that is similar to, and derived from, the
operation of rubbing leaf between the palms of the hand in primitive
chinese fashion.

What the machines do in the process of rolling is another long chapter
- that we shall discuss some other time - have kipped it for the
moment.

The green color of the leaves diminishes and the brown or coppery
colour of the oxidation products begins to appear.

At this stage there are a number of points related to the design of
rollers and to procedure that require emphasis because they affect the
whole course of manufacture and the quality of finished tea. The first
is that the onset of rolling is accompanied by the evolution of heat.

Pressure, by consolidating the leaf, confines the accumulated heat and
that is why, in traditional rolling programmes, periods with and
without pressure are generally alternated.

Excessive pressure in the early stages of rolling affects the physical
appearance of the tea.

The number of times a batch of leaf is rolled varies according to the
type of tea to be produced, the degree of wither of the leaf and the
kind of roller used. In general the lightly withered leaf common to
Assam or African procedures receives a smaller number of rolls than
medium or hard withered leaf in Ceylon. The usual range is from three
to five rolling periods. The aim is first to twist the leaf and then
progressively to break it up into small particles by increased
pressure till the major portion has been sifted through the green leaf
sifters.

ROLL BREAKING AND GREEN LEAF SIFTING

On discharge from the roller the leaf mass is more or less compressed
into lumps. These are broken up in the sifting process by the machine
which usually combines the operation of roll breaker and sifter. In
essence this is a rectangular sieve, set at a moderate angle,
mechanically agitated. The roller discharge is fed into a hopper in
which beaters revolve to break up the mass, after which the tea falls
onto the sieve and slowly travels to the other end for discharge. In
the course of this passage the smaller particles fall through.

The roll breaker and green leaf sifter performs three essential
functions. In the first instance it cools the leaf and thus prevents
the retention of excessive heat: secondly, it aerates the mass, and
thirdly, by sieving out particles of small size, it seperates leaf
into portions that will be reasonably uniform in their rate of
fermentation. To achieve this uniformity careful operation is needed.
The leaf should be fed continuously at an even rate and be well spread
across the width of the sieve.

FERMENTATION

Fermentation starts in the rollers but is continued in the dhool
stage. The sifted dhools (smaller particles) are spread out in thin
layers, in order to continue the oxidative processes. There is great
variety in the materials that are used to accomodate this spread - out
leaf. Tiles, cement and aluminium are most commonly used, the
essential point being that they should be easily cleaned. The
thickness of spread controls three important factors, the temperature
of the leaf, the rate of moisture loss and the access of oxygen. With
layers two inches thick temperature losses sufficient to retard
fermentation are not likely. Some factories install air - conditioning
plant to ensure controlled conditions. Good air circulation without
draughts is needed to attain good fermentation conditions. In hot
climates the air is kept humid with less than 4 degree F. hygrometric
difference. In colder regions the circulating atmosphere is
artifically heated. In either event moist air, to prevent surface
drying, is advisable. For economical working it is better to ferment
in a special fermentation room whose atmospheric conditions can be
easily controlled.

During fermentation the leaf changes colour and becomes a dark copper
colour. The typical aroma develops and by the subjective judgement of
its intensity the period necessary for completion is judged. Time of
fermentation is reckoned from the time at which rolling begins and it
should be as short as practicable. After four and a half hours there
is appreciable loss of quality.

FIRING

The general principle adopted in firing is that of subjecting the
fermented tea to a forced blast of hot air in such a manner that the
hottest air comes first into contact with the driest tea. To bring
this about the older driers, some of which are still in use, were
provided with a banked series of perforated trays carrying the dhools,
which were systematically altered in position as the drying operation
proceeded; a fresh tray being inserted at the exhaust end as the trays
were moved and the final one removed.
A similar pattern of movement was also provided for in machines which
had fixed trays built in narrow strips which could be mechanically
tilted so as to discharge their leaf onto the tray below, leaving the
upper one ready to load with the next portion of unfired dhool.

Modern machines employ the principle of perforated sections mounted on
an endless chain. The sections are arranged in a tier of six units
which alternate in their direction of motion. The tea is fed onto the
top section, and moves in conveyor - belt fashion till it discharges
onto the tray immediately below, which is moving in the opposite
direction; and so on till the dried tea is discharged at the bottom.
Hot air is provided by means of a furnance or steam boiler through
which pass tubes connecting with the outer atmosphere.

Thickness of spread, speed of trays and volume or air blown can all be
regulated at will.

Inlet temperatures usually range from 180 degree F to 200 degree F.,
according to the degree of wither, and outlet temperatures are in the
range of 120 degree F. to 130 degree F.

During the drying process the enzyme responsibly for fermentation is
inactivated. After the tea is dry maturation processes occur but these
are not due to enzyme activity. The manner of firing plays an
important role in determining the quality. Teas fired at high
temperature are deficient in pungency, quality and flavour, but their
keeping properties are satisfactory. Contrariwise teas can be
satisfactorily fired at temperatures as low as 160 degree F. provided
that the final moisture content is correct. These teas retain their
quality and flavour but deteriorate on storage.

GRADING AND SORTING

Grading is carried out for the most part on mechanically oscillated
sieves, similar in genral principle to those used in the green stage,
and fitted with meshes of appropriate size.

The grades in general production are named as follows: Broken Orange
Pekoe; Broken Pekoe; Orange Pekoe; Pekoe; Souchong; Broken Orange
Pekoe Fannings; Fannings and Dust.

Before tea is packed the accumulated series of daily batches of each
grade are bulked and mixed in order to ensure as high a degree of
uniformity as possible. The tea is then packed into chests holding
approximately 100 lb. or 50 lb. (half chests). These chests are
usually of plywood lined with almunium foil and paper and sealed with
similar material.

Hope i have been able to make things simpler - please feel free to ask
any questions that you may have.

Regards
Ankit
www.xanga.com/lochantea