During normal conditions, it is always preferable to use ambient air as long as it has drying properties. If at all hot air is required, it would be ideal to use it during the early part of withering when the leaf is still turgid. Warm air should not be used to wither during later stages, since the leaf takes a temperature nearing the dry bulb temperature.
It would be better and more accurate to express the status of wither in terms of percentage of moisture content in the withered leaf. If the percentage of moisture content at the end of withering is the same irrespective of moisture content of the green leaf, then by and large the physical condition will remain the same. Withering to a constant moisture content every day is impractical even with the greatest care.

The following two conditions are essential for good withering: storage of fresh leaf for a minimum period of nine hours is absolutely essential to allow chemical changes to take place whether a physical wither is desired or not, to make a product with required characteristics, this is referred to as chemical wither. Physical wither is necessary for good fermentation.

GREEN LEAF SIFTING Extraneous matter such as stones, sand or metal pieces may find their way in the leaves brought into the factory; if such materials are fed into the fine-tuned, continuous machines, the moving parts will be severely damaged. Similarly if the leaves were not fed evenly into these machines, they could become jammed or would not function efficiently. Hence green leaf sifting is essential prior to processing.

The green leaf sifter is essentially a device for introducing a continuous even flow of withered leaf to the CTC processing section. It is a vibrating tray, which is perforated with holes or is of a wire mesh. Powerful magnets have been provided in the green leaf sifter to remove any iron pieces present along with the leaf.

RECONDITIONING In South India, secondary grades and other residues which are obtained while cleaning the primary grades are ground and recycled with the withered leaf. This process is known as reconditioning. The primary objective of this practice is to produce grainy grades as well as tea of high density. It also helps to minimize or eliminate secondary grade teas.

The quantity of recycled material, known as recondition dust, varies from factory to factory, it depends on the quality of green leaf, the moisture content of the withered leaf and the standard of machinery available. The percentage of RC is mostly expressed on the weight of green leaf or made tea basis. However, there is a wide variation in the moisture content of green leaf and thereby the quantity of made tea produced. So quantifying the amount of RC material for the made tea to be produced depending upon the green leaf conditions is difficult. The best practice is that the amount of RC should be calculated on the withered leaf weight basis. However, as already mentioned variation in the moisture content of the withered leaf should be controlled to a narrow range say 2 to 3 percent.

LEAF CONDITIONING The leaf shredder and rotor vane combination has been found to be ideal to pre-condition the leaf for CTC processing. The output of both these machines should match with the CTC as well as Drier capacities.

Shredding of withered leaf into fine particles increases the rotorvane capacity and helps efficient mixing of the leaf with reconditioned dust in the rotorvane. The macerated leaf from the shredder has to be in the form of 'chutney'. To ensure this the shredder blades have to be changed every week. It is important that the weight of each blade should be less than one Kg. and properly balanced on the knife edge. Reduction of gap between two blades progressively helps to achieve better results.

Rotorvane is essentially a large mincing machine and is imperative to precondition the leaf suitable to be fed into the CTC machine as well as for better fusion of RC material with withered leaf. There are two sizes, one with cylinder of 20.3 cm (8") diameter and the other large machine with a cylinder dia of 38.1 cm (15"). The leaf is processed in this cylinder in which a rotor provided with vanes rotates between resistors thereby propelling the leaf forward and discharging through an end plate.

The leaf is distorted and shredded as it moves along the cylinder and cut into small pieces by the revolving cutter through which it must pass before it can leave through the apertures of an iris diaphragm. For good results the rotorvane should crush the leaf along with the RC dust at the maximum possible pressure. The 8" rotorvane exerts a much higher pressure on the leaf than does the larger machine, consequently the leaf is much more damaged when passing through it. In the larger rotorvane, a cone end plate is attached at the discharge end to increase the pressure; the leaf is discharged between the gap of the cone and the cylinder; the inner of the cylinder and cone are provided with battens in order to increase the efficiency of crushing.

ROLLING After preconditioning, the leaf is passed through four or five CTC machines arranged in tandem. The CTC machine essentially consists of two contra-rotating toothed rollers of equal diameters(20.3 cm or 8") . Depending upon the processing capacity required, rollers with different width are used ie. 61 cm (24"), 76.2 cm(30"), 91.4cm(36"). The two rollers rotate at different speeds. A slow speed roller; high speed roller ratio of 1:10 with speeds between 70:700 rpm and 100:1000 rpm has good effect. The slow speed roller act initially as a conveyor apart from providing a surface for cutting. In order to derive the maximum benefit of a good cut, the drop point should be adjusted behind the crown of the slow speed roller, so that the leaf is conveyed into the cutting area. Otherwise, a portion of the leaf gets thrown over the high speed roller, thereby, losing the benefit of cut.

A number of hollow segments of 2" width are mounted side by side on a mandrel to form a roller. Even spaced, helical grooves are formed along the circumference by a standard angular milling cutter. The teeth are formed by cutting circumferential grooves on the roller which has the helical grooves. Each tooth has two longitudinal characteristics, the shoulder and the back slope. The ratio of the length of the shoulder to the back slope projection is known as the profile or style ratio which influences quality. As a general rule, a style ratio of 5:3 will produce a grainy tea with higher dust percentage.

Precision in sharpening and machining the CTC roller surfaces are the keys to good CTC manufacture. Quality CTC teas cannot be made if roller teeth are worn out or damaged. It is, therefore, imperative that sharpening of segments is done precisely and on schedule.

The speed of the high speed and low speed roller in conventional CTC roller will be 700 to 750 and 70 to 75 RPM, respectively. For Senova (13" dia ) roller, the speed will be 560 to 600 and 56 to 60 RPM. The deviation in the speed of a few rollers will result in erratic High Speed Roller (HSR), Low Speed Roller (LSR) ratio.

The linear speed difference between the rollers should be checked periodically to enhance the appearance of made tea and to improve the recovery percentage. Difference in the diameter of rollers leads to different speed in rollers. The pulley size also influence the speed. To achieve 10:1 ratio, proper matching of equal diameter rollers is essential.