Textile dyeing and finishing is a complex, systematic process involving raw materials, semi-finished goods, weaving, dyeing, and final finishing. Among them, spinning, weaving, and dyeing + printing + finishing are three relatively independent sectors.

Main Processes in Spinning:

Opening and cleaning
Carding
Combing
Drawing
Roving
Ring spinning

Main Processes in Weaving:

Winding
Warping
Sizing
Drawing-in
Weaving
Fabric finishing

Dyeing and Finishing Workflow:

Fabric preparation → Stitching → Singeing → Cold pad batching → Desizing, scouring, bleaching → Mercerizing → Pre-setting → Paste preparation → Printing (flat screen or rotary screen) → Steaming → Soaping → Heat setting → Shrink-proofing → Calendering → Final inspection and packing

Process Breakdown

1. Singeing

Purpose: Remove surface fuzz to enhance fabric smoothness, gloss, and appearance. It prevents uneven dyeing and printing defects and improves anti-pilling performance, especially for synthetic fibers. The fabric becomes cleaner and crisper in hand feel.

Cold Pad Batch: After singeing, the fabric is cooled and rested for over 20 hours.

2. Desizing, Scouring, and Bleaching

(1) Desizing

Purpose: Remove sizing agents applied during weaving to improve absorbency, reduce chemical consumption, and enhance final product quality.

Methods:

Hot water desizing: Effective for fabrics sized with water-soluble materials such as sodium alginate or cellulose derivatives.
Alkaline desizing: Suitable for starch-based sizes, using 10–20 g/L sodium hydroxide solution at 60–80°C for 6–12 hours.
Enzymatic desizing: Uses α-amylase to hydrolyze starch without damaging the fibers; fast and efficient.
Oxidative desizing: Involves hydrogen peroxide or sodium perbromate; efficient but must be controlled to avoid cellulose damage.

(2) Scouring

Purpose: Remove natural impurities like pectins, waxes, and seed residues to improve wettability and whiteness.

(3) Bleaching

Purpose: Eliminate residual natural pigments to improve brightness and prepare fabric for dyeing or printing.

Common agents: Sodium hypochlorite, hydrogen peroxide, sodium chlorite.

3. Mercerization

Process: The fabric swells irreversibly when treated with strong alkali, transforming cellulose I into cellulose II.

Key Factors:

Caustic soda concentration
Temperature
Treatment time
Tension applied to fabric

Benefits:

Improved dimensional stability and reduced shrinkage
Increased dye uptake and absorbency
Enhanced luster
Modified mechanical properties (e.g., reduced tensile strength)

Types:

Dry mercerization: Performed at room temperature on dried fabric. Stable results but energy-intensive.
Wet mercerization: Performed on wet fabric; saves energy and improves evenness but requires precise moisture control.
Hot caustic mercerization: Better penetration and even alkali uptake, used for heavier fabrics.

4. Pre-setting (Pre-heat Setting)

Purpose: Thermally stabilize fabric structure, eliminate wrinkles, and improve dimensional stability and surface smoothness.

Critical Conditions:

Temperature (most important)
Treatment time
Applied tension
Use of swelling agents

Note: Sensitive shades (e.g., grey, army green, khaki) may shift color under heat and must be monitored post-setting.

5. Dyeing

Basic Steps: Dye adsorption → Diffusion → Fixation

Common Dye Types:

Dye Type	Suitable Fibers	Advantages	Disadvantages
Direct dyes	Cotton, linen, silk, wool	Simple application, low cost	Poor wash/light fastness
Reactive dyes	Cotton, linen, silk, wool	Excellent wash fastness	Moderate wet/acid fastness
Sulfur dyes	Cellulose fibers	Good wash/sunlight fastness	Poor rubbing fastness, shade variation
Disperse dyes	Polyester, nylon, acetate	Short cycle, good brightness	Sensitive to alkaline hydrolysis
Cationic dyes	Acrylic, cationic polyester	Bright shades, strong intensity	Limited depth
Vat dyes	Cotton and other cellulose	Excellent overall fastness	Expensive, some colors cause damage under light

Dyeing Methods:

Yarn dyeing: Hank dyeing, package dyeing, warp-beam dyeing
Fabric dyeing: Rope dyeing, jig dyeing, pad dyeing, continuous dyeing

Key Factors:

Time: Sufficient for diffusion and fixation
Temperature: Affects fiber swelling, dye solubility, rate and depth of dyeing
pH: Impacts dye behavior and shade accuracy
Liquor ratio: Fabric weight to water volume
Dye concentration: Measured in g/L, affects intensity and uniformity
Auxiliaries & water quality: Crucial to achieve reproducible results

Color Fastness: Grades range from 1 to 5, with 5 being the best. Fastness requirements vary by application (e.g., apparel, home textiles, etc.).

Standard Light Sources:

D65: International daylight (most widely used)
TL84: Fluorescent store light (Europe/Japan)
CWF: Cool white fluorescent (US retail/office)
UV: For optical brighteners and fluorescent detection
A: Simulated sunset light, reference only

6. Steaming and Soaping

Steaming: Used after printing (except for ice dyes and soluble vat dyes). Steaming promotes moisture absorption, dye fixation, and penetration into the fiber.

Soaping: Crucial post-steaming step. Removes unfixed dyes, prevents re-deposition, and improves colorfastness through dispersing, chelating, and suspending actions of soaping agents.

7. Shrink-Resist Finishing (Sanforizing)

Purpose: Mechanically reduce fabric shrinkage caused by internal tension during wet processing. Helps stabilize fabric width and improve dimensional accuracy.

8. Calendering, Electric Calendering, and Embossing

Calendering: Uses heat and pressure to flatten the fabric surface or create fine diagonal lines.

Flat calendering: Hard + soft rollers, results in a smooth, crisp hand feel.
Soft calendering: Two soft rollers yield a softer hand and milder sheen.

Electric Calendering: Uses heated rollers for gloss enhancement.

Embossing: Engraved metal rollers press patterns into the fabric under heat and pressure for decorative effects.

Note: Depending on the fabric type, additional processes like sueding, napping, shearing, raising, or softening may also be applied.