In the dyeing and finishing of textiles, many factors affect the final results throughout the process. Therefore, various quality problems often occur in actual mass production, among which color-related issues are the most frequent, and color difference ranks first. This article explains the causes of color difference and dyeing defects and how to solve them.

Color difference can be classified as follows:

a. Lab-to-bulk color difference (difference between lab dip and bulk production);

b. Batch color difference, including inter-batch color difference, within-batch bath-to-batch color difference, and within-bath tube-to-tube color difference;

c. Other types of color difference, such as head-tail color difference, left-center-right color difference, and color change after post-treatment and finishing.

At present, dyeing and finishing are mostly carried out according to the color specified by customers, who often have very high, even strict, requirements for color matching.

Lab-to-bulk color difference refers to the color deviation between lab samples and bulk production. It is the first problem that must be faced and solved in mass production.

It can be seen that the more consistent the dyeing method between the lab and bulk machine, the smaller the lab-to-bulk color difference. However, in practice, high consistency is rarely achieved; usually only a certain similarity can be reached. For some processes such as jig dyeing, the difference can be quite large.

Therefore, successful lab testing does not guarantee successful bulk production, especially in the development and trial of new products, new materials, and new processes. Lab procedures cannot always be directly copied to the workshop.

For this reason, besides using suitable and advanced lab dyeing equipment, a middle-scale trial on one piece of fabric or 1–2 cones before bulk production is highly recommended. Middle-scale trials are much closer to actual production than lab tests.

One-shot lab-to-bulk matching has long been a technical goal and is fundamental to preventing bath-to-batch color difference. It depends not only on advanced testing equipment but also on technical and management levels. It is one of the key technologies for dyeing and printing enterprises and a prerequisite for the widely promoted “Right-First-Time Dyeing”.

The shift from traditional “adjustment after production” to “prediction and control before production” is the premise of achieving one-shot matching. Meanwhile, mastering the color change rule throughout the production process requires detailed and systematic basic work.

Batch color difference includes differences between different production batches and within the same batch. It has long been a persistent problem in dyeing production involving many factors, and its prevention requires a systematic approach.

The main causes are summarized into four aspects:

a. Different origins, batches, and lots of fiber raw materials lead to different dye uptake rates;

b. Different origins, batches, and lots of dyestuffs, auxiliaries, and chemicals result in differences in active ingredient content;

c. Unreasonable machine allocation and scheduling (different dyeing machines have inherent shade differences, and improper arrangement causes inter-batch and bath-to-batch variations);

d. Non-standard execution of process conditions (determined by staff quality and management level), covering not only dyeing but also pretreatment and finishing.

Any problem in the above four aspects can cause batch color difference. If both technology and management are insufficient, multiple factors may occur simultaneously, making root-cause analysis very difficult.

Bath-to-batch color difference is another common issue in batch dyeing.

Reasonable grouping of grey fabrics in pretreatment is the premise. The biggest influence comes from the operational discipline of frontline workers: whether processes are strictly followed and consistently implemented across operators, machines, and shifts.

Accurate weighing and dosing of dyes and chemicals are essential. However, errors often occur in warehouses, so double-checking systems are necessary. Even with automatic weighing and feeding systems, failures or human errors may occur after long-term operation. Lack of maintenance and inspection can lead to large batch quality issues.

In addition, lab dipping is closely related. If color correction relies heavily on repeated dye additions, bath-to-batch color difference will only worsen.

Tube-to-tube color difference occurs in multi-tube parallel jet or overflow dyeing machines.

Such high-capacity machines are designed to reduce or eliminate bath-to-batch difference but may introduce tube-to-tube variation due to their operating mechanism. More parallel tubes increase single-bath capacity but also raise the risk of tube difference. Excessive parallel connection is not advisable.

Prevention starts with uniform grey fabric grouping in pretreatment. Maintaining stable machine performance is even more critical than for single-tube machines, together with strict operation and real-time monitoring.

Inspection, identification, and correction of tube-to-tube difference are far more complicated than bath-to-batch difference, especially for blended fabrics such as polyester-acrylic, polyester-cotton, and viscose-nylon, where tube difference may reoccur during overdyeing. Late detection leads to high rework costs.

Head-tail color difference often occurs in continuous padding and jig dyeing due to the machine structure.

It is less common in loose batch dyeing, but can still happen if operators rush production by adding dyes and raising temperature too quickly.

In addition, insufficient cleaning of sublimed dyestuff in polyester heat-setting machines can cause sublimation staining on subsequent fabrics, especially when changing from dark to light shades. Residual dyestuff being gradually washed off also results in head-tail color variation.

This mainly occurs in padding and jig dyeing, mostly caused by mechanical factors.

In padding: uneven pressure or misalignment of padding rollers leads to asymmetric pick-up; malfunction of the padding liquor replenishment system causes left-right concentration difference.

In jig dyeing: deformed or poorly maintained cloth expanding rollers result in uneven squeezing across the width.

Thinner, less absorbent fabrics and sensitive three-primary-color shades are more prone to left-center-right difference. Non-standard chemical feeding and improper tension control for thin fabrics also cause uneven dye distribution.

For loose dyeing, left-center-right difference should not occur in theory. However, edge-center color difference often appears in knitted fabrics due to severe edge curling that cannot open in the dyeing machine. This is a material-related issue requiring solutions in weaving and dyeing processes.

Some dyes exhibit thermo-chromism, so proper dye selection is essential.

Post-treatment and finishing auxiliaries—including fixing agents, crosslinking agents, softeners, water and oil repellents, and coating agents—inevitably affect the final shade. Longer processes, higher temperatures, and more auxiliaries increase color change risk.

Even mechanical finishes such as napping and sanding, which are chemically independent, change surface light reflection and cause apparent color difference—a visual effect rather than chemical change. Hue remains stable, but depth and brightness vary. Such physical color changes still require pre-control.

In a comprehensive sense, dyeing is truly completed only after all finishing, full cooling, and stable color for subsequent sewing.

It is unrealistic to expect zero color change from finishing auxiliaries. This issue belongs to the scope of lab-to-bulk matching and also faces lab-bulk deviations. Therefore, lab dipping must simulate real production conditions and be verified in middle and bulk trials.

Note that finishing auxiliaries mainly improve fastness, handle, and functional properties. Dyestuffs remain the dominant factor in shade adjustment.

Mastering color evolution rules and focusing on pre-control are the fundamental solutions.

A special mention is the yellowing of amino silicone softeners.

They are widely used for excellent handle and durability, but higher amino content improves softness while increasing yellowing. Higher temperature and longer finishing time aggravate oxidative yellowing.

Despite chemical modification, contradictions remain. Extra-white and bright light shades (especially violet) require careful selection, sometimes sacrificing some softness to maintain whiteness.

Continuous technical innovation drives industry development. However, new achievements in technology, chemicals, and equipment have a limited valid period.

To maximize efficiency and profit, rational and efficient use of raw materials, energy, and water is essential. Right-First-Time Dyeing is the practical expression of this principle.

Right-First-Time means no unplanned rework or redyeing throughout production. Achieving it requires a comprehensive system including technology, management, equipment, and workforce quality.

It greatly improves productivity, saves resources, reduces energy consumption and emissions, and enhances enterprise profitability.

Traditional quality management relies on final inspection and grading, when defects are already fixed. The medical model of epidemic prevention provides inspiration: prevention over cure is highly effective in controlling dyeing defects and minimizing costs.

“Prevention over cure” is the philosophy of modern quality management: taking proactive measures from the source, based on production records, and preventing defects at every potential stage. By perfecting each process, the final result is guaranteed. Thus, prevention over cure is the ideological foundation of Right-First-Time production.

Color difference arises from many factors: variations in fibers, grey fabrics, dyes, and chemicals; machine conditions; processes, technology, management, and personnel.

Every stage from pre-preparation, pretreatment, dyeing, post-treatment to finishing can cause color difference, making it the most frequent and top-three critical problem in dyeing production.

Although color correction, rework, and redyeing are sometimes unavoidable, they are passive remedies. Some textiles do not allow rework at all.

Therefore, prevention-oriented strategies for all potential causes should be the leading principle in production, technical, and quality management of dyeing and finishing.