Introduction to wet processing

1. Introduction to Wet
Processing

2. Why Wet Process??
Exclusively carried out under wet conditions and require
bulk quantities of water
Wet Processes
 Sizing
 Desizing
 Scouring
 Bleaching & Optical Whitening
 Mercerization
 Dyeing
 Printing
 Finishing

3. Grey ClothSize
Antistatic /
Spin Finish
Natural
Colouring
Materials
Wax, Oil &
Gum
Dyeing
Finishing
De-sizing
Scouring
Bleaching
Mercerizing
Printing
•Grey Checking
•Purching
•Burling
•mending
•Stitching
•Shearing & Cropping
Singeing

4. Preparatory process for cloth
• Loom state fabric has 3 types of impurities
– Natural
• Inherent in cotton fibre
– Added
• Sizing ingredients
• Antistatic
– In process
• Fragments of cotton seeds
• Leafy material
• Oil stains etc.

5. Perching

6. • Grey Checking
– Mending visual defects
• Stitching
– Stitched to make a lot
– Improper stitches can lead to creases in dyeing
& tearing of selvedges
• Shearing & Cropping
– To remove fibres and loose yarns from the
surface of the fabric

7. • Singeing
– To produce smooth surface finish or fabrics from staple fibres
– The presence of hairs produces a fuzzy appearance
– Removal of these hairs are done during singeing operations
– Fabrics are passed over a heated copper plate or above a gas flame
– The fibre ends burn off
– Heat sensitive fibres wouldn’t be singed due to formation of balls
– Filament yarns do not require singeing

8. • Sizing
– The process by which yarn is sized with starch or PVA (Polyvinyl
Alcohol) or CMC (Carboxy-methyl Cellulose) to give necessary
smoothness and strength for weaving
• Desizing
– The process by which the sizing components (already applied to yarn)
are removed from the grey cloth to make it suitable for
• Dyeing
• Printing
• Other Finishing processes

9. • Scouring
– The process by which the natural impurities are removed
• Greases
• Waxes
• Fats
• Other impurities
• Bleaching
– The process to remove the natural colouring materials and to render
the cloth white

10. • Mercerization
– The process to impart lustre, strength, dye affinity
– Carried out for cotton fabrics only
– Mercerization can be of two types
• With tension (lustre increases)
• Without tension (luster does not increase)
• Dyeing
– It is a process to impart colour on the fabric / yarn or fibre
– Large number of dyes are available
– Example: Direct dye, Basic dye, Acid dye, Metal Complex dye, Vat Dye
etc.

11. Fibre, dyes and dye-fibre bonds
Fibre Dye class having affinity Type of dye-fibre bonds
Cellulosic: Cotton, jute,
rayon
•Direct, vat, sulphur
•Reactive
•Vanderwals force
•Covalent bond
Protein: Wool, silk, nylon •Direct, acid, metal
complex, and basic
•Reactive
•Ionic or electrostatic
bonds
•Co-valent bond
Polyester •Disperse Vanderwals force and
hydrogen bonding
Acrylic •Basic •Electrostatic bond

12. • Printing
– It is a localized dyeing effect
– Dyes are applied as a thick paste along with
thickener
– The fabric is then treated with steam for dye fixation
on the applied areas
• Finishing
– It is the final operation carried out after dyeing or
printing
– It is done to impart some special aesthetic look or
some functionality to the fabric

13. What is finishing ??????
• Finishing is a final process given to a textile
material to
– Give a good appearance
– Desirable feel
– Impart certain durable properties
• Stiffness
• Softness
• Wash and wear finish
• Water repelling finish
• Fire proof finish etc.
– To impart some desired functional properties

14. Classification of finishing
• Classification according to the nature of finish
According to the nature of Finish
Physical or Mechanical Finish
1) Calendering
2) Sanforizing etc.
Chemical Finish
1) Mercerization
2) Easy care finish etc.

15. • Physical or Mechanical Finish
– Mechanical / Physical finishes involve specific
physical treatment to a fabric surface to cause a
change in the fabric appearance
– Also known as dry finish
• Chemical Finish
– Chemicals are used followed by curing or drying
– Also known as wet finish

16. Classification of finishing
• Classification according to degree of permanence
According to degree of permanence
Permanent Finish
Temporary Finish
Durable Finish
Semi - Durable
Finish

17. Definitions
• Permanent Finish: Usually involve a chemical change in fibre structure
and do not change or alter through out the life of the fabric
• Durable finish: Usually last through the life of the article, but
effectiveness becomes diminished after each cleaning; and near the end
of the normal use life of the article, the finish is nearly removed
• Semi-durable finish: Last through several laundering or drycleanings and
many are renewable in home laundering or drycleaning
• Temporary finish: Are removed or substantially diminished the first time
the article is laundered or drycleaned

18. Classification of finishing
• Classification according to performance
According to Performance
Aesthetic Finish– Improved / Altered
Appearance
1. Calendering
2. Fulling
3. Mercerization
Functional Finish– Improved / Altered
Performance
1. Antiseptic
2. Antistatic
3. Crease resistant
4. Durable press
5. Flame resistant
6. Mothproofed
7. Shrinkage control
8. Soil release
9. Water and stain repellent
10. Waterproof

19. • Aesthetic Finish
– These finishes modify the appearance and /
or hand or drape of fabrics
• Functional Finish
– These finishes improve the performance
properties of fabrics