Wet Processing I
MD. MH Tomal
BUTEX
Wet processing
• In general, The wet processing of textile involves all the processes of a
textile that includes some form of chemical treatment.
• From prehistoric times, man has been fascinated by colour. Colour is
everywhere. The clothes we wear, our surroundings, both natural and
manmade are abundant with colour. Color is an extremely important
aspect of modern textiles & wet processing of textile.
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Reference Book
• Chemical Technology in the pretreatment Processes of Textiles
S.R. KARMAKAR
• Textile Preparation & Dyeing
A.K. Roy Choudhury
• Chemistry & Technology of fabric preparation & finishing
C. Tomasino
• Dyeing & chemical Technology of Textile fibers
E.R. Trotman
• Basic Principle of Textile Coloration
A.D. Broadbent
History #
• 3000 B.C. in China, it is believed that dyeing was practised.
• Around the period of 2500 B.C. dyeing was then already an
established practice.
• Until 1856, all textiles used throughout the world were natural dyes
• In 1856 William Henry Perkin discovered the first synthetic dye
stuff "Mauveine" (aniline, a basic dye) while searching for a cure for
malaria and a new industry was begun.
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SEQUENCES OF WET PROCESSING
Grey Fabric inspection
Sewing / Stitching
Shearing & Cropping
Singeing
Desizing
Scouring
Bleaching
Mercerization
Coloration
Dyeing Printing
Washing
Finishing
Mechanical Chemical
Inspection
Folding & Packaging
Delivery
Grey fabric
• Grey fabric ( also known as“greige” fabric) is the raw,
unprocessed and unfinished fabric taken directly from
a loom.
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Grey Checking & Grey Testing
• Here the fabric is checked carefully that is there any deformities or not.
Here the yarn density, number of ends & number of picks per unit length,
yarn strength is also examined. Proper repairing of the fabric is also
done here.
Shearing or Cropping
• Shearing is an operation consists of cutting the loose strands of fibres
from either surface of a fabric with a sharp edged razor or scissors.
Good cropping reduces the tendency of blended fabrics to 'pill'.
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Singeing
The verb ‘singe’ literally means ‘to burn superficially’.
The aim of singeing is to burn-off the protruding fibres
and hairs from the fabric surface. This process is mainly
done by gas flame.
Desizing
• The aim of desizing is to remove the sizing materials
of the fabric which was applied at the warp yarns of
the fabric at the time of weaving.
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Scouring
The aim of scouring is to remove all the natural & added
impurities mainly the hydrophobic impurities.
Mercerization
Mercerization is a treatment of cotton with a strong caustic alkaline solution
in order to improve the luster, hard and other properties, was nameed after its
discoverer, John Mercer, and has been in use for sometime. It has been seeing
an increase in application recently.
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Bleaching
The aim of bleaching is to remove the natural colours
i.e. some yellowish colour of the fabric.
Textile Wet Processing
Textile wet processing can be thought of having three stages,
a) Pretreatment (or preparation),
b) Coloration (dyeing or printing)
c) Finishing
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Textile Wet Processing
a) Pretreatment (or preparation):
Exist to ensure that the textile has the right physical and chemical
properties to enable it to be colored or finish.
Purpose:
• To remove added and natural impurities from textile material
• Removal of impurities to the maximum extent possible with minimum effect on fibre
strength.
• To impart desirable properties to textile material
For example
• Scouring ,Bleaching ,Heat setting etc.
Preparation/Pretreatment steps
Singeing
Desizing Typically a woven
cotton fabric would be
prepared by sequence
Scouring of process as shown.
In case of knitting
Bleaching sizing step is not
Involved so desizing is
not required
Mercerization
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Textile Wet Processing
b) Coloration (dyeing or printing):
Exist to provide the textile with color either for aesthetic reasons or
for some functional purpose, determined by the end use of the product.
For example
• Dyeing
• Printing
Dyeing:
Dyeing is a chemical process which involves the migration of the colorants with a suitable vehicle(dye solution) to
the surface of the fibres in the fabric being coloured, (the diffusion of the dye through the fibres and the fixing of
the dye by chemical bonding.)
Printing:
Localized application of dyestuff or pigments on fabric according to the predetermined design is called printing.
Textile Wet Processing
c) Finishing:
Any operation (other than preparation & coloring) for improving the
appearance or usefulness of a fabric after it leaves the loom or knitting machine can be
considered finishing. Finishing give the last chance to provide the properties that
customers will value.
For example
• Flame retardant finish
• Calendaring etc.
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