Jigger

This machine is most commonly used for dyeing almost all kinds of cotton fabrics at full width. The fabric is dyed in this form on the jigger to a larger extent than in any other form. The jigger is a simple machine which consists of a V-shape trough fitted with two draw rollers one along each side of the machine. At the commencement of dyeing, cloth in open width is wound on one of these rollers called the 'let-off roller from which it is unwound and passed through the dye-liquor in the trough with the help of guide rollers and an immersion roller on to the other roller called the take-up roller’ on which it is wound.The roll of cloth at either. end is stitched with about : 5 m grey cloth called the 'end piece' so that during the run of the cloth through the liquor from one draw roller to the other, a part of the end piece remains on the roller hut the end portions of the cloth to be dyed pass through the liquor (which otherwise  would have remained undyed ). The passage of cloth from one draw roller to the other through the dye-liquor is called 'one end' or 'one turn' .The number of 'ends' to be given depends on the depth of shade absorption capacity of the cloth, type of dyestuff used and the time required for one 'end' .An even number of ends
jigger machine
is always given to prevent a portion of cloth getting a darker shade than the other. Most of the penetration of the dye-liquor or actual dyeing takes place when the cloth is resting on the roller.. before going through the liquor again and not when the cloth is running through the liquor. The dye-liquor is heated by perforated or closed steam coils and the liquor can be drained off through an outlet. Even when the liquor in the trough is at the boil, the temperature of the roll of the cloth is usually about 70°c; dyeing are not suitable for jigger dyeing, unless enclosed jiggers are used for the purpose.

The cloth has to be uniformly wound on the draw roller in such a way that no part of the selvedge comes out of the roll one during winding. If a part of the selvedge comes out of the roll,  then while dyeing vat dyes, the portion containing the leuco vat  get oxidation by air then when it enters the dye-liquor again, it picks up more dye than the rest of the cloth thus giving a darker ends selvedge. When dyeing naphthol colors, the selvedge shade


becomes lighter because the naphthol decomposes duc to the ac of CO2, from
If the jigger is to be stopped during dyeing, the entire s cloth so wound on one of the draw rollers and the roll is kept rotating that the liquor does not drain down and make the lower half darker than the upper half of cloth
The older type of jiggers were made of wooden roller and wooden troughs; such troughs absorb colour and get stated and their cleaning is difficult They are used to dye dark shade or for dyeing the same shade again and again. But they have been practically superseded by modern jiggers which are made  metal or stainless steel and have smooth surface when can be easily cleaned. They can be heated quickly and also cooled quickly Both the rollers are power driven and can run at constant speed; tension can be controlled with ease and varied as required The direction of motion can be reversed automatically at the end of each tarn by means of a time switch and can be stopped after the required number of turns. A differential driving mechanism  is used for changing the speed so that the cloth move at a uniform speed; otherwise the differential in speed results a tailing effect ie, weakening of the shade. Expanders are also fitted to keep the fabric free from creases and at full width So preventing uneven dyeing
 In the earlier machines, the m:l ratio was very high, now  the jiggers are constructed with small trough in winch the ml ratio is 1:5 or I:4 thereby saving consumption of water, steam  and chemicals (like caustic soda and sodium hydrosulphite when dyeing vat dyes). For better penetration of liquor in the case of The heavy fabrics like canvas or drill, heavy rubberized rollers mounted is  on a moveable frame are used to press the draw rollers and  squeeze the liquor. Improved jiggers have recently been developed is  which ensure constant tension and constant speed and ate provided with direct and indirect heating and automatic temperate of the dye-bath

Disadvantage of Jigger Dyeing

   It is a batch-wise or discontinuous process: only a small lot dyeing of say. 100 m can be dyed at a time.


During dyeing. the fabric is pulled from one roller to the other exerting considerable lengthwise tension (ranging from 5 to 10 % ) which is injurious - to delicate fabrics like viscose rayon fabrics which have low tensile strength in wet condition, knitted goods can be damaged. The special pebble appearance of seer sucker fabrics (obtained by crimp or crepon style of printing) gets distorted by stretching the fabric lengthwise.


3 If the cloth is not properly batched and the selvedges are non-coincident, then on dyeing, such selvedges come out lighter or darker than the body of the cloth


4 In the case of heavy fabrics like canvas or drill, only surface dyeing of the material takes place particularly with vat dyes because of the difficulty of penetration of the dye-liquor, in spite of increasing the time of contact. For such fabrics the pigment padding method has to be used by padding the fabric with a suspension of a vat dye in the unreduced state and then developing it with caustic soda and hydrosulphite followed by oxidation.



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