Basic Knowledge of Dyes

1. What Are Dyes?

A dye is a colored organic compound that gives color to textile fibers. However, not every colored organic compound can be used as a dye.

In general, a suitable dye should meet four basic requirements.

Color Strength

A dye must produce a sufficiently strong and even color at a practical concentration.

Dyeing Ability

A dye needs to have a certain affinity for textile fibers. This allows it to attach to or combine with the fiber effectively.

Solubility

A dye should dissolve directly in water or become water-soluble through a chemical reaction.

Color Fastness

The color should remain durable after dyeing. It should resist fading or changing during washing, rubbing, light exposure, and daily use.

2. Dyes and Pigments

Some colored substances do not dissolve in water and have little or no affinity for textile fibers. Therefore, they cannot enter the fiber structure directly.

Instead, these substances rely on a binder to attach mechanically to the fabric surface. They are called pigments.

Pigments are usually combined with dispersing agents, wetting agents, water, and binders to create a pigment printing system. Unlike dyes, pigments are used more commonly in textile printing than in conventional dyeing.

3. The Development of Dyes

In 1857, British chemist W. H. Perkin industrialized the production of mauveine, also known as aniline purple. It became the first commercially produced synthetic dye.

As a result, 1857 is often considered an important dividing point in dye history:

• Before 1857: extraction and processing of natural dyes
• After 1857: production and development of synthetic dyes

According to the Colour Index, more than 7,000 synthetic dyes and organic pigments have been developed worldwide. More than 2,000 of them are still produced regularly.

Although synthetic dyes have a history of only around 160 years, they have developed rapidly and now serve many textile applications.

4. Main Dye Classification Methods

The textile industry generally classifies dyes in two main ways:

1. Chemical classification, based on molecular structure
2. Application classification, based on dyeing performance and usage

Classification by Chemical Structure

Common chemical categories include:

• Azo dyes
• Anthraquinone dyes
• Aryl methane dyes
• Indigoid dyes
• Sulfur dyes
• Phthalocyanine dyes
• Nitro dyes
• Nitroso dyes
• Methine and polymethine dyes
• Stilbene dyes
• Heterocyclic dyes

Each chemical group offers different properties, including color range, solubility, fiber affinity, and color fastness.

Classification by Application

According to their application, dyes include:

• Direct dyes
• Acid dyes
• Basic dyes
• Cationic dyes
• Reactive dyes
• Azoic dyes
• Disperse dyes
• Vat dyes
• Sulfur dyes
• Condensation dyes
• Fluorescent whitening agents
• Oxidation dyes
• Solvent dyes
• Polypropylene dyes
• Food colorants

Different dye classes work with different fibers and require different dyeing conditions. For example, reactive dyes are widely used for cotton, while disperse dyes are mainly used for polyester.

5. How Are Dyes Named?

Dyes come in many colors, types, and performance levels. Therefore, the industry uses a systematic naming method to describe their application, color, and characteristics.

China introduced a three-part dye naming system based on the Draft Naming Scheme for Dye Products, which began trial implementation in January 1965.

A dye name generally contains three parts:

1. Prefix
2. Color name
3. Suffix

The Prefix: Application Category

The prefix usually indicates the dye class or its main application.

Common prefixes include:

• Acid
• Direct
• Direct Fast
• Direct Blend
• Basic
• Cationic
• Reactive
• Vat
• Soluble Vat
• Sulfur
• Disperse
• Naphthol
• Azoic Base
• Azoic Salt
• Condensation

The prefix helps users identify which fibers and dyeing processes the product may suit.

The Color Name: Main Shade

The color name describes the shade produced on the textile material.

Instead of listing every shade separately, color names are usually grouped into several main color families:

• Yellow and gold
• Orange and red
• Pink and purple
• Blue
• Green
• Brown
• Olive
• Gray
• Black

Words such as Light, Bright, and Deep further describe the tone.

For example:

• Bright Red indicates a vivid red shade.
• Deep Blue indicates a darker blue tone.
• Light Yellow indicates a softer yellow shade.

The Suffix: Additional Information

The suffix uses letters and numbers to describe additional properties, including:

• Color tone
• Physical form
• Special performance
• Intended use
• Dye strength
• Other dyeing characteristics

6. Common Letter Codes

Codes for Color Tone

A
A code derived from a traditional dye name, such as Lake Blue A or Acid Scarlet A.

B
Indicates a blue or bluish-green shade.

G
Indicates a yellow or green shade.

R
Indicates a red shade.

F
Indicates a pure or clean color tone.

D
Indicates a deep or relatively dull shade.

These codes help distinguish dyes that share the same basic color name but have different undertones.

Codes for Properties and Applications

AS
Used for names in the azoic naphthol dye series, such as AS-D.

B
Used for certain bis-triazine reactive dyes, such as Megafix Golden Yellow BES.

C
May indicate chlorine-bleach resistance, as in Vat Blue BC for cotton. It may also refer to hydrochloride salts of azoic bases, such as Yellow Base GC.

D
May indicate dyes suitable for high-temperature dyeing of blended fibers, such as Direct Blend Yellow D-RL. It may also refer to high-temperature disperse dyes or vat dyes suitable for printing.

Because the same letter may have different meanings in different dye systems, users should always check the manufacturer’s technical documentation.

7. Dye Strength and Percentage Markings

Dye names may include strength markings such as:

• 100%
• 150%
• 200%

These figures describe the relative strength of the dye. They do not necessarily indicate the exact percentage of dye in the product.

For example, a manufacturer may define a standard product as having 100% strength. A product marked 50% would then have approximately half the strength of that standard.

However, different manufacturers may use different reference standards. Therefore, strength percentages from different suppliers cannot always be compared directly.

Manufacturers may also add fillers or processing auxiliaries, including:

• Accelerating agents
• Dispersing agents
• Solubilizers
• Extenders
• Other processing aids

For this reason, users should review the product’s technical data sheet before comparing prices or preparing dyeing recipes.

8. Example: Reactive Brilliant Red M-8B 150%

Let us take Reactive Brilliant Red M-8B 150% as an example.

• Reactive: The dye belongs to the reactive dye category.
• Brilliant Red: The dye produces a vivid red shade.
• M: Indicates the specific type or series of reactive dye.
• B: Indicates a blue undertone.
• 8B: Indicates a stronger blue undertone than the basic B shade.
• 150%: Indicates the relative dye strength compared with the manufacturer’s standard product.

This name provides information about the dye’s application category, color, undertone, product series, and strength.

Conclusion

Dyes are more than colored substances. A suitable textile dye should offer good color strength, effective fiber affinity, suitable solubility, and reliable color fastness.

Chemical classification explains the molecular structure of a dye, while application classification focuses on how the dye performs during production.

The three-part naming system also provides practical information about a dye’s category, color, tone, performance, and strength.

Once these basic rules are understood, dye names become much easier to read, compare, and apply in textile