Solving Severe Turquoise Shade Spotting on Viscose Fabric

— A Technical Case Study by Our Company’s Engineer in Indonesia

In textile dyeing, turquoise shades are widely recognized as one of the most sensitive and high-risk colors. Even minor process deviations or hidden contamination can be dramatically amplified, eventually appearing as shade spots or color unevenness on the fabric surface.

Recently, at the request of the Managing Director of an Indonesian textile company, our company’s engineer traveled on-site to investigate and resolve a long-standing issue: persistent shade spotting on viscose (rayon) jersey fabric dyed with G-133 Turquoise, for which the root cause could not be identified locally.

This article documents the full investigation, root-cause analysis, and preventive solutions.

1. Problem Identification: When Production Abnormalities Signal a Deeper Issue

1.1 Phenomenon Description

After dyeing viscose jersey fabric in turquoise shade, the fabric surface showed numerous irregular spots of varying sizes:

• When viewed normally, the spots appeared darker and more vivid than the surrounding fabric

• Under transmitted light, the spotted areas were clearly deeper in shade

• The spots were randomly distributed and severely affected visual uniformity

As a result, the entire batch was classified as unacceptable for shipment.

The main dye used was G-133 Turquoise.

1.2 Initial Judgement and Failed Corrective Attempts

Because the color difference was obvious and could not be eliminated by normal reprocessing (strip and redye trials still showed spots), the local technical team initially concluded that the problem originated from pretreatment contamination.

Corrective actions attempted:

• Increased dosage of scouring and degreasing agents

• Strengthened scouring conditions

However, no improvement was observed.
To reduce losses, the company eventually decided to overdye the fabric to black.

1.3 Key Findings by Our Engineer

Upon taking over the case, our engineer started from the greige fabric, rather than adjusting dyeing parameters.

a) Transmitted Light Inspection

Using a fabric inspection machine with backlighting, faint but irregular dark patches could already be observed on the greige fabric.

b) Water Drop Test (Critical Evidence)

• Normal areas: water droplets spread and penetrated quickly (good hydrophilicity)

• Suspected areas: water formed beads or penetrated very slowly (hydrophobic behavior)

A classic indication of silicone oil contamination

c) Laboratory Reproduction

Lab dyeing using the same recipe reproduced the same spotting phenomenon, excluding dye batch issues.

d) Root Cause Localization

Production records and on-site inspection finally pointed to the pre-setting process.

Investigation revealed that:

• The previous batch required silicone softener application

• The padding trough and rollers were not thoroughly cleaned according to SOP

• Visible silicone oil residues remained in the padding system

After thorough cleaning, subsequent viscose turquoise dyeing showed no recurrence of the problem.

2. Root Cause Analysis: Why Silicone Oil Causes Dark Turquoise Spots

This issue is not a simple “poor dye uptake” problem, but a dynamic and complex abnormal dye accumulation process.

2.1 Nature of the Contamination: Silicone Oil Characteristics

• Silicone softeners are inherently:

• Highly hydrophobic

• High-molecular-weight polymers

• Designed to form smooth, water-repellent films on fiber surfaces

• Under pre-setting heat, residual silicone oil can partially fix and penetrate into the fabric structure

Once thermally set, such residues are difficult to remove by conventional scouring.

2.2 Affected Substrate: Dyeing Sensitivity of Viscose Fiber

Viscose (regenerated cellulose fiber) features:

• High hydrophilicity

• Porous internal structure

• Large specific surface area

Advantages:

• Fast dye uptake

• High color yield

Disadvantage:

Extremely sensitive to surface cleanliness and uniform chemical conditions

Any localized loss of hydrophilicity directly leads to dyeing unevenness.

2.3 Color Sensitivity Amplifier: Turquoise Reactive Dyes

Turquoise shades are typically produced using dyes such as:

• Reactive Turquoise KN-G

• G-133 Turquoise

These dyes are characterized by:

• Large molecular size

• High substantivity

• Poor diffusion ability

• High sensitivity to minor process variations

They are widely recognized as one of the most difficult shades to dye evenly.

2.4 Mechanism of Dark Spot Formation (Key Process)

Normal Areas

• Clean, hydrophilic fibers absorb dye evenly

• Proper fixation with alkali

• Unfixed dye is removed during washing
  Uniform and stable shade

Silicone-Contaminated Areas

1️⃣ Initial Blocking Stage
Silicone film prevents proper wetting and dye penetration, resulting in lower initial dye uptake.

2️⃣ Partial Film Breakdown
High temperature, mechanical agitation, and fabric friction partially damage the silicone layer.

3️⃣ Abnormal Delayed Dye Uptake
At this stage, normal areas have largely completed fixation, while contaminated spots begin absorbing dye under abnormal conditions.

4️⃣ Secondary Floating Dye Accumulation

• Fixation efficiency in these spots is low

• Large amounts of unfixed dye migrate and accumulate

• Silicone’s strong affinity traps these floating dyes, making them resistant to soaping

After washing, the contaminated areas appear darker than the normal fabric.

✅ Conclusion

This is not a case of “insufficient dyeing,”
but a typical “initial blocking followed by abnormal dye enrichment” phenomenon caused by silicone oil contamination.

3. Solutions: From Emergency Correction to Long-Term Prevention

A. Immediate Corrective Actions (For the Affected Batch)

1. Damage Assessment and Decision
   Turquoise shade cannot mask defects. Overdyeing to dark shades (black or navy) is the most economical solution.

2. Special Cleaning Before Redyeing

• High-temperature alkaline washing with emulsifiers

• Use of dedicated silicone oil removal agents

• Intensive rinsing to restore fabric hydrophilicity

1. Careful Redyeing

• Select dyes with high build-up and coverage

• Strict control of dyeing parameters to minimize secondary risks

B. Long-Term Preventive Measures (Core Value)

1. Strengthen Equipment Cleaning SOP

• Clear cleaning triggers (shade change, process change, silicone use)

• Standardized cleaning sequence

• White fabric confirmation and signed responsibility records

2. Optimize Production Scheduling

• Dye from light to dark shades

• Schedule bright and sensitive colors immediately after equipment cleaning

• Group silicone-based finishing orders to reduce changeovers

3. Establish Key Control Points

• Mandatory water drop hydrophilicity test before dyeing

• Clear equipment status labeling: “Cleaned / To Be Cleaned”

4. Enhance Technical Awareness

Pretreatment is not an auxiliary step — it is the foundation of dyeing quality.

Final Remarks

Turquoise shade spotting may appear to be a dyeing issue on the surface,
but fundamentally it reflects equipment management, process continuity, and quality awareness.

Through systematic investigation and mechanism-based analysis, our company’s engineer not only resolved the immediate production issue, but also helped the customer establish a repeatable and preventive quality control framework, transforming firefighting into long-term risk prevention.