DESIZING PROCESS & IT'S OVERVIEW

Complete Guide to Desizing Process in Textile Industry

Definition

Desizing is the process of removing the sizing materials (usually starch-based) applied on warp yarns before weaving. This is done to prepare the fabric for further wet processing like scouring, bleaching, dyeing, or printing.

Objective of Desizing

- Remove size coatings (starch, PVA, CMC, etc.)
- Improve fabric absorbency and wetting properties
- Enhance dye penetration and evenness
- Reduce risk of patchy dyeing or uneven printing
- Clean the surface for smooth further processing

Process Flow Chart

Grey Fabric → Desizing → Washing → Scouring → Bleaching → Mercerizing → Dyeing/Printing

Desizing Parameters

- Water temperature: 60–100°C (depending on size type)
- Time: 15–30 minutes
- Enzyme concentration: 1–3 g/L (for enzymatic method)
- Wetting agent concentration: 0.5–1 g/L
- Fabric speed in machine: 10–50 m/min (continuous process)

Chemicals Used & Their Purpose

Amylase Enzyme: Breaks down starch molecules used as size.
Oxidizing Agents (e.g., H2O2): Used in oxidative desizing for synthetic sizes.
Acids (Dilute HCl or H2SO4): Used in acidic desizing for water-soluble sizes.
Wetting Agents: Help penetrate water into the fabric and improve desizing efficiency.
Detergents: Help in removing loosened size and surface impurities.

Types of Fabrics Used

- 100% Cotton woven fabrics
- Blended fabrics with high cotton content
- Viscose and linen fabrics (depending on size used)

Properties Achieved After Desizing

- Increased hydrophilicity
- Cleaner and more uniform fabric surface
- Better dye affinity
- Enhanced softness and brightness

Desizing Machines

- Pad-Steam Range: Fabric is padded with desizing solution, stored in a J-box for reaction, and washed.
- Continuous Washing Range: Includes application zone, dwell zone, and washing compartments for continuous operation.

Temperature and chemical control is automated in modern machines for quality consistency.

Changes Occur During Desizing

- Size layer is broken and washed away
- Fabric becomes soft and hydrophilic
- Surface is ready for uniform chemical penetration in next stages
- Reduces chances of uneven coloration or chemical patching

Examples

- Desized cotton sheeting for uniform reactive dyeing
- White cotton shirting post-desizing used in scouring and bleaching
- High-quality mercerized fabric begins with enzymatic desizing