Viscose Dyeing Process: Step-by-Step Guide

Viscose fabric, known for its silk-like feel and versatility, demands a precise dyeing process to maintain color consistency, durability, and softness. Whether you’re working with 100% viscose or a blend with Lycra, understanding the dyeing process ensures vibrant and long-lasting results.

Recipe:
Shaiful Alam 
Assistant General Manager 
(Fabric Dyeing, Finishing & Quality)

This guide breaks down the viscose dyeing process, covering every crucial step—from fabric preparation to final finishing.

Viscose Fabric and Its Dyeing Challenges

What is Viscose?

Viscose, a semi-synthetic fiber derived from wood pulp, shares properties with both natural and synthetic fibers. It is:

• Highly absorbent
• Breathable
• Soft and smooth
• Prone to shrinkage and creasing

Why is Viscose Dyeing Unique?

Unlike cotton or polyester, viscose has a high water-retention capacity.

It makes dye absorption more unpredictable. Common dyeing challenges include:

• Uneven dye uptake
• Fabric strength reduction in wet conditions
• Sensitivity to high temperatures

Step-by-Step Viscose Dyeing Process

Table: 100% Viscose or 95% Viscose & 5% Lycra Dyeing Process

Pre-Treatment Process

Before dyeing, viscose fabric undergoes pre-treatment to remove impurities and improve dye uptake.

Scouring

• Removes natural oils, waxes, and dirt
• Uses a mild alkali solution at 50°C–60°C
• Improves uniform dye penetration

Bleaching

• Enhances brightness and whiteness
• Uses hydrogen peroxide (H₂O₂) at 80°C
• Maintains fabric strength while removing natural color

Dyeing Stage

Selecting the Right Dye

Common dyes for viscose:

• Reactive Dyes: Offer excellent color fastness and bright shades.
• Direct Dyes: Cost-effective but prone to fading.
• Vat Dyes: Superior wash and light fastness.

Preparing the Dye Bath

• Water Temperature: 40°C–50°C for reactive dyes
• Dye-to-water Ratio: 1:10 for uniform absorption
• pH Level: Maintained between 6.5 and 7 for stability

Dyeing Process

Chemical Addition:

• Salt (30–50 g/L) for dye fixation
• Soda ash (5–15 g/L) for pH control

Gradual Heating:

• Raise temperature to 80°C–90°C
• Hold for 30–60 minutes

Cooling and Rinsing:

• Gradual cooling to 50°C to prevent fiber damage
• Multiple rinses to remove unfixed dye

H2: Post-Dyeing Treatment

After dyeing, finishing processes ensure durability and softness.

Neutralization

• Uses acetic acid (1 g/L) to remove alkali residues
• Prevents yellowing and improves color retention

Soaping

• Removes unfixed dyes
• Uses non-ionic detergents at 60°C

Softening

• Cationic softeners improve hand feel
• Silicone-based softeners enhance smoothness

Quality Control and Final Finishing

Ensuring consistent quality involves several tests:

• Color Fastness Test: Checks resistance to washing and sunlight
• Shrinkage Test: Ensures dimensional stability
• pH Test: Confirms skin-friendliness (ideal range: 6.5–7.5)

The final finishing steps include:

• Calendering: Enhances fabric sheen
• Sanforization: Controls shrinkage
• Packing: Protects against contamination

Conclusion

Mastering the viscose dyeing process is crucial for achieving vibrant, long-lasting colors. By following each stage—from pre-treatment to post-finishing—you can ensure high-quality dyeing with excellent durability.

Understanding the right temperature, pH levels, and chemical combinations plays a significant role in successful dyeing. With the right approach, you can make viscose fabrics look stunning while maintaining their softness and breathability.

FAQ

By following these steps, you can achieve perfectly dyed viscose fabric with a rich, even color and a luxurious feel!