Sizing Operation in Textiles: Principles, Processes, Materials, and Industrial Practice

Sizing is one of the most critical preparatory operations in textile manufacturing, particularly in weaving. It plays a decisive role in determining weaving efficiency, fabric quality, loom productivity, and overall manufacturing cost. Despite being a temporary treatment, sizing has a long-lasting influence on yarn behavior during weaving and subsequent processing stages.

This article provides a comprehensive and technically detailed explanation of sizing in textile manufacturing, covering its objectives, working principles, materials used, process steps, machinery, and quality considerations from an industrial perspective.

Introduction to Sizing in Textile Manufacturing

Sizing in textile refers to the application of a protective adhesive coating on warp yarns before weaving. Warp yarns are subjected to continuous friction, tension, bending, and abrasion during weaving. Without adequate protection, yarn breakage becomes frequent, leading to lower loom efficiency and inferior fabric quality.

The sizing process creates a thin film over the yarn surface, binding loose fibers, improving yarn strength, reducing hairiness, and enhancing resistance to mechanical stress. This treatment is mainly applied to spun yarns such as cotton, viscose, and blended yarns, though filament yarns may also be sized under specific conditions.

Objectives of the Sizing Process

The primary goal of the sizing process is to improve warp yarn performance during weaving. However, its objectives extend beyond simple strength enhancement.

Key objectives include:

• Increasing tensile strength of warp yarns

• Reducing yarn hairiness and lint formation

• Improving abrasion resistance

• Enhancing yarn smoothness for easy shedding

• Reducing end breakage on the loom

• Improving weaving efficiency and fabric uniformity

• Ensuring consistent yarn behavior throughout the weaving cycle

An effective sizing operation balances strength improvement with flexibility, ensuring the yarn does not become brittle or stiff.

Importance of Sizing in Textile Production

In modern high-speed weaving machines such as air-jet and rapier looms, yarns are subjected to significantly higher mechanical stresses compared to conventional looms. This makes sizing in textile production even more essential.

Without proper sizing:

• Warp breakages increase dramatically

• Loom stoppages rise, reducing productivity

• Fabric defects such as broken ends and streaks appear

• Subsequent processes like desizing and dyeing become problematic

Thus, the sizing process in textile manufacturing is not merely a preparatory step but a productivity-enhancing and quality-assuring operation.

Sizing Materials Used in Textiles

Sizing materials, also known as size agents, are selected based on yarn type, fabric end-use, weaving method, and desizing requirements. These materials are broadly classified into natural, modified natural, and synthetic sizes.

Natural Sizing Materials

• Starch (maize, potato, tapioca)

• Wheat starch
  Natural sizes are economical and biodegradable but have limitations such as brittleness and poor flexibility.

Modified Natural Sizes

• Oxidized starch

• Etherified starch

• Enzyme-modified starch
  These offer improved film-forming properties, flexibility, and easier desizing.

Synthetic Sizing Materials

• Polyvinyl alcohol (PVA)

• Polyacrylates

• Carboxymethyl cellulose (CMC)

Synthetic sizes provide excellent abrasion resistance and flexibility but are more expensive and pose environmental concerns if not properly recovered.

Additives in Size Paste

To improve performance, several additives are incorporated:

• Softeners to improve flexibility

• Lubricants to reduce friction

• Antistatic agents to control static electricity

• Preservatives to prevent microbial growth

Classification of Sizing Based on Yarn Type

Sizing of Cotton Yarns

Cotton yarns require sizing due to their short staple length and high hairiness. Starch-based or blended size recipes are commonly used.

Sizing of Blended Yarns

Blended yarns such as polyester-cotton require careful formulation to balance adhesion and flexibility.

Sizing of Filament Yarns

Filament yarns generally require minimal sizing, mainly to reduce static charge and friction.

Steps Involved in the Sizing Process in Textile Industry

The sizing process in textile production involves several sequential steps, each contributing to the final yarn quality.

1. Preparation of Size Paste

The size paste is prepared by cooking the sizing materials in water at controlled temperature and agitation to ensure uniform viscosity and dispersion.

2. Yarn Sheet Formation

Warp yarns from the warper beam are separated and arranged into a sheet to allow uniform penetration of size liquor.

3. Size Application

The yarn sheet passes through a size box containing the prepared size solution. Proper immersion ensures uniform coating.

4. Squeezing

Excess size liquor is removed using squeezing rollers. This step controls size pick-up percentage and uniformity.

5. Drying

Sized yarns are dried using steam-heated cylinders or hot air chambers to form a continuous protective film.

6. Winding onto Weavers Beam

After drying, the sized yarn sheet is wound onto a weaver’s beam, ready for loom insertion.

Sizing Machinery Used in Industry

Conventional Slasher Sizing Machine

Used for cotton and blended yarns with multiple drying cylinders and size boxes.

Multi-Cylinder Sizing Machine

Provides controlled drying and uniform size distribution.

Single-End Sizing Machine

Used for technical textiles and special yarns requiring precise control.

Modern Automatic Sizing Machines

Equipped with:

• Online viscosity control

• Automatic moisture regulation

• Digital tension control

• Energy-efficient drying systems

Key Parameters Affecting Sizing Quality

Several technical parameters determine the success of sizing in textile processing:

• Size concentration and viscosity

• Size pick-up percentage

• Yarn tension during sizing

• Drying temperature and duration

• Moisture content of sized yarn

• Uniformity of size application

Incorrect control of these parameters can lead to brittle yarns, excessive stiffness, poor desizing, and weaving problems.

Advantages of Proper Sizing

• Significant reduction in warp breakage

• Improved loom efficiency

• Higher fabric quality

• Better control over weaving defects

• Reduced production downtime

• Enhanced consistency in large-scale manufacturing

Limitations and Challenges of Sizing

Despite its advantages, the sizing process also presents challenges:

• Increased processing cost

• Requirement of desizing before dyeing and finishing

• Environmental impact of synthetic size agents

• Risk of uneven sizing if poorly controlled

Modern textile mills address these challenges through optimized formulations, size recovery systems, and eco-friendly sizing materials.

Desizing: A Necessary Follow-Up Process

Since sizing materials are temporary, they must be removed after weaving. Desizing is essential to ensure proper dye penetration and fabric softness.

Common desizing methods include:

• Enzymatic desizing

• Oxidative desizing

• Acid desizing

• Hot water washing

The choice of method depends on the type of size used during the sizing process in textile manufacturing.

Conclusion

Sizing in textile manufacturing is a technically sophisticated and economically vital operation that directly influences weaving performance and fabric quality. A well-designed sizing process enhances yarn strength, reduces breakage, improves loom efficiency, and ensures smooth downstream processing.

With advancements in sizing materials, machinery automation, and sustainability-focused practices, modern sizing operations are becoming more efficient, precise, and environmentally responsible. For textile students, technicians, and industry professionals, understanding the fundamentals and industrial practices of the sizing process in textile production is essential for achieving consistent and high-quality woven fabrics.