Introduction to Chemical Processing Notes
Subject Overview
Introduction to Chemical Processing familiarises students with the role chemical processing plays in the design and production of textiles — the preparatory, dyeing and printing stages every fabric passes through before it reaches a designer's hands. You'll study grey fabric inspection and impurities, the preparatory processes for cotton, wool and silk (scouring, bleaching, mercerisation), the classification and application of dyes, and close with dyeing stages/
Subject at a glance
5
Units
21
Topics
2
Credits
5
Infographics
Unit-wise Syllabus
5 units — open any unit for detailed topic-wise notes, diagrams and important exam questions
Grey fabric inspection, characteristics and classification of impurities
Natural
Wax, pectins, seed husks, colour
Added
Size (starch), spinning oils
Accidental
Dirt, stains, rust
Study guide
This unit begins with grey fabric inspection and the types of impurity in grey fabric. Understanding impurities explains why each later process is needed.
- Preparatory process for cotton — stitching
- singeing
- desizing
- scouring
- bleaching and mercerisation
- preparatory process for wool and silk
- preparation of blends
- 1Singeing
Burn off surface fibres
- 2Desizing
Remove starch size
- 3Scouring
Remove wax and oils
- 4Bleaching
Remove natural colour
- 5Mercerisation
Caustic soda: lustre, strength, dye uptake
Study guide
You study the preparatory processes for cotton (stitching, singeing, desizing, scouring, bleaching, mercerisation) and for wool and silk and blends. Learn the order of the processes and the purpose of each.
- Definition of colour
- dyes and pigments
- classification of dyes
- application of dyes on textiles
Reactive
Cotton, viscose
Bright, fast: bonds chemically
Vat
Cotton
Excellent fastness: denim indigo
Acid
Wool, silk, nylon
Applied in an acid bath
Disperse
Polyester
High temperature dyeing
Basic
Acrylic
Very bright colours
Study guide
You study colour, dyes and pigments, dye classification and the application of dyes on textiles. Match each dye class with the fibre it suits.
- Stages of dyeing
- dyeing machinery
- dyeing of blends
- dyeing defects
Jigger
Open-width woven fabric
Cotton fabrics
Winch
Fabric in rope form
Knits and delicate fabrics
Jet
Fabric in rope, high pressure
Polyester
Package dyeing
Yarn on perforated packages
Yarn for coloured weaves
Study guide
You study the stages of dyeing, dyeing machinery, dyeing of blends and dyeing defects. Learn the common defects and their causes.
- Methods of printing
- styles of printing
- special prints
- printing defects
Direct
Colour printed onto the fabric
Most printed cotton
Discharge
Print removes dyed ground colour
White pattern on dark ground
Resist
Paste blocks dye from areas
Batik, Bagru dabu
Special prints
Effects added to fabric
Flock, foil, burn-out
Study guide
You study printing methods and styles, special prints and printing defects. Compare direct, discharge and resist styles with examples.
Why Introduction to Chemical Processing Matters
Colour and finishing decide how fabric looks and sells. Chemical processing knowledge is central to roles in processing houses, quality control and textile design.
How to Prepare for Introduction to Chemical Processing
- Make a flowchart of cotton preparatory processes.
- Prepare a table of dye classes, fibres and fastness properties.
- Visit a dyeing or printing unit if possible.
Introduction to Chemical Processing: Frequently Asked Questions
What is mercerisation?
Mercerisation treats cotton with strong caustic soda under tension to increase lustre, strength and dye affinity.
What is the difference between dyeing and printing?
Dyeing colours the whole fabric uniformly, while printing applies colour in patterns to selected areas.