1. Incoming goods inspection ,Qc  shade seggreation & Lot/Batch preparation

• Visual & physical inspection of rolls/sheets: check for damage, stains, oil, prior finishes, size type (starch, PVA, resin), GSM, and composition labels.

• Sampling: take laboratory swatches for small-scale trials if the fabric or previous processing is unknown.

• Weighing & batching: determine batch size (kg) and prepare batch sheets.

• Chemical & utility check: verify inventory for enzymes, peroxide, acids, surfactants, sequestering agents, softeners, and availability of hot water/steam, compressed air, effluent system ready.

• Health & safety: ensure PPE, MSDS accessible, and staff briefed.

Reason: misidentifying sizing (e.g., PVA vs starch) or previous treatments results in failed desizing or fiber damage downstream.

2. Desizing — purpose and method

Purpose: Remove film-forming sizing materials (starch, carboxymethylcellulose (CMC), PVA, waxes) used in weaving/warping. Proper desizing restores absorbency and preps fibre for bleaching/dyeing.

Process choices:

• Enzymatic desizing (α-amylase for starch): widely used, effective at moderate temperatures and pH. Eco-friendly.

• Chemical desizing (caustic / alkaline): used for PVA and stubborn sizing; requires higher temperatures / alkali and sometimes special PVA-degrading agents.

• Oxidative or hydrolytic treatments for specific sizing chemistries.

Typical operating window (starch):

• Temperature: 60–70 °C

• pH: 6.5–8.5 (enzyme-specific)

• Enzyme dose: 0.1–0.5 g/L (or according to supplier)

• Time: 20–30 minutes

• Liquor ratio (L:R): 1:5 to 1:10 for continuous padded or jet wash lower L:R can be used.

Key control checks:

• Iodine test for residual starch.

• Absorbency test (drop test).

• Monitor bath conductivity and pH.

Notes for PVA: PVA requires specific alkali/heat or PVA-degrading enzymes—confirm sizing type before selecting method.

3. Enzyme treatment (Stone Enzyme /bio-scouring / bio-polishing)

Purpose: Remove residual natural impurities (pectins, proteins, waxes) and fibrils to improve absorbency, whiteness, smoothness and reduce pilling.

Enzyme types & uses:

• Pectinases: remove pectins in cotton blends.

• Proteases: for proteinaceous contaminants (wool blends or silks).

• Cellulases (bio-polishing): remove microfibrils to give softer hand, reduce pilling (low concentrations, tightly controlled).

• α-Amylase: overlaps with desizing for starch removal.

Operating guidelines:

• Temperature: 40–60 °C (depends on enzyme, cellulases tend to work at lower temp around 45 °C)

• pH: 4.5–8.5 (enzyme specific; cellulases prefer mildly acidic to neutral)

• Time: 20–60 minutes

• Enzyme dose: supplier specified — often 0.1–1 g/L

• Liquor ratio and gentle mechanical action to avoid surface damage.

Critical controls:

• Don’t expose active enzyme bath to high alkalinity or temperature that denatures it.

• After enzyme treatment, perform a thorough wash to stop enzyme action (alkaline or hot water can deactivate, but controlled neutralization/rinse is preferred).

Benefits: Lower chemical consumption, better whiteness, reduced energy use vs aggressive chemical scouring.

4. Bleaching (oxidative whitening)

Purpose: Remove natural color impurities to prepare a white/base substrate for dyeing or tinting. Hydrogen peroxide (H₂O₂) is the industrial standard for cellulosic fibers.

Key chemicals:

• Hydrogen peroxide (stabilized solutions)

• Alkalis (soda ash, caustic in controlled small amounts)

• Stabilizers / activators (sodium silicate, sodium stannate or commercially formulated stabilizers)

• Sequestering agents / chelants (EDTA types or safer alternatives) to bind metal ions which catalyze peroxide decomposition.

Operating window (typical):

• Temperature: 60–70°C (often 60–70 °C)

• Time: 30–90 minutes

• H₂O₂ concentration: 2–6 g/L (depending on whiteness target and fabric)

• pH: 9–10.5 during bleaching (alkaline medium makes peroxide more reactive)

• Liquor ratio: 1:5–1:10 (continuous lines lower)

Process notes:

• Control of metal ions is crucial; trace iron/copper accelerate peroxide decomposition and cause uneven bleaching or fabric damage.

• Peroxide stability: avoid sudden temperature rise or addition of incompatible chemicals.

• Follow supplier’s recommendations for stabilizer selection and dose.

Quality metrics:

• Whiteness index or reflectance measured by spectrophotometer.

• Tensile strength tests before/after bleaching to detect over-oxidation.

5. Neutralization (post-bleach)

Purpose: Remove residual peroxide and bring fabric pH to a safe level before further chemistry; prevents fiber damage and prepares for detergents/dyes.

Chemistries used:

• Acids: acetic acid, citric acid in diluted form to lower pH.

• Reducing agents (if needed to destroy residual oxidant): sodium bisulfite or sodium thiosulfate (used cautiously as they can affect subsequent dyeing).

Operating notes:

• Target pH after neutralization: approx 5.0–6.5 (depends on next step; dyeing often needs specific pH)

• Add acid slowly while continuously stirring and monitoring pH to avoid localized over-acidification.

• If residual H₂O₂ is measured, a short reducing step may be applied but must be followed by thorough rinsing.

Controls:

• Continuous pH monitoring; do not overshoot.

• Test strips or pH meter in pad/exhaust are used.

6. Clean / Detergent wash

Purpose: Remove emulsified oils, surfactant-soluble contaminants, and residues from previous steps—ensures a clean substrate for even tinting/dyeing.

Chemicals:

• Non-ionic surfactants (excellent wetting and emulsification)

• Low foaming detergents for high-mechanical washers

• Builders/sequesterants to aid soil removal

Operating parameters:

• Temperature: 40–60 °C

• Time: 10–30 minutes

• Detergent dose per supplier guidelines (commonly 1–5 g/L depending on machine type)

Notes:

• Avoid high foaming systems in continuous lines.

• Final conductance and turbidity of rinse indicate cleanliness.

7. Rinse (counter-current recommended)

Purpose: Remove soluble chemicals and reaction by-products after each major step to avoid carryover and interference.

Best practices:

• Counter-current rinsing saves water: final rinse water is cleanest and flows to earlier rinse step.

• Typical sequence: 2–4 rinses with rising water quality.

• Measure conductivity, pH, and turbidity to determine adequacy of rinses.

Parameters:

• Ambient to slightly warm depending on carryover chemical solubility.

• Each rinse 5–15 minutes in batch systems; continuous systems sized accordingly.

Water management: Reuse and recovery (e.g., treat first rinse for reuse) lowers effluent load.

8. Tinting (light shade application)

Purpose: Apply a pale shade or shade correction to get consistent appearance or achieve a desired pastel tone on bleached substrate.

Dye selection:

• Use reactive dyes for cellulose (cotton), disperse for synthetics, acid dyes for protein fibres. For tinting on bleached cotton, low-strength reactive dyes are common.

• Choose auxiliary salts (sodium sulfate) and alkali (soda ash) based on dye class.

Application systems:

• Padding: fabric passes through pad box with dye liquor and squeezed to an uptake level.

• Exhaust (vat/jet): low-shade dyeing at controlled temperature.

• Pad-batch: pad then hold for fixation at ambient or mild temperature.

Controls:

• Bath exhaustion monitoring and even pick-up (pickup % in padding).

• Shade reproducibility checks with spectrophotometer.

Important: If tinting is barely perceptible, ensure fixation does not cause uneven blotching; pilot trials on lab scale recommended.

9. Fixing (dye fixation / after-treatment)

Purpose: Ensure that the applied tint/dye is securely bonded to the fibre and that unfixed dye is removed/stabilized to achieve wash-fastness and minimize skew or bleeding.

Fixation methods (depending on dye type):

• Reactive dyes (cellulosic): alkali addition (soda ash) to form covalent bond; temperature/time control critical.

• Disperse dyes (synthetics): heat fixation (thermosol or high-temperature exhaust).

• Acid dyes (protein): fixation via pH and time at moderate temperatures.

• Fixing auxiliaries: polymeric fixatives, leveling agents, or cold pad-batch fixing (allows fixation at room temperature over hours).

Example (reactive dyes):

• After dye exhaustion, add sodium carbonate (soda ash) to reach pH ~10–11 for reactive fixation, hold at 40–60 °C for the required time, then wash out hydrolyzed/unfixed dye in a soaping step (detergent + hot water).

Follow-up steps:

• Soaping or hot detergent wash to remove hydrolyzed/unreacted dyes.

• Thorough rinsing to reduce unfixed dye in effluent.

Quality tests:

• Wash fastness (ISO tests), rubbing/crocking tests, and spectral checks.

10. pH control — continuous monitoring

Purpose: Ensure correct pH at each handover point; many dyeing chemistries and finishing agents require specific pH ranges to work properly and to avoid damage.

Common set points:

• Post-bleach neutral: pH 5–6

• Pre-reactive dye fixation (if alkaline fixation required): pH 9.5–11

• Softener application: often pH ~5–6 for cationic softeners

• Final pH for dispatch: industry often targets pH 5–7 depending on fabric and end use.

Control methods:

• Inline dosing pumps controlled by pH sensors for continuous lines.

• Manual titration with acetic/citric acid or soda ash in batch processes.

Checks: Use both pH meter and pH strips for confirmation; calibrate meters frequently.

11. Softener application (hand feel improvement)

Purpose: Improve tactile properties—softness, drape, anti-static behavior. Softener selection affects durability and other properties (e.g., oil repellency).

Types:

• Cationic softeners: bond well to negatively charged cellulosic fibres.

• Silicone softeners: excellent hand, durable feel; often used in blends.

• Non-ionic emulsions: milder, less yellowing tendency.

Process:

• Bath application (pad or exhaust) followed by mild rinse or direct hydro-extract and dry depending on formulation.

• Typical doses: 3–12 g/L (or specified on supplier data).

• Temperature: 25–40 °C for pad/exhaust application.

Effects to monitor:

• Yellowing potential (especially with some cationics).

• Effect on dye fastness (some softeners can reduce crock/wet fastness).

12. Hydro-extraction

Purpose: Remove bulk water prior to drying—reduces drying time and energy consumption.

Equipment: Centrifugal hydro-extractors, continuous squeeze rollers, or high-speed scroll extractors.

Targets:

• Residual moisture: 30–50% retained depending on downstream dryer; high-speed extraction can reduce to <30% for tumble dryer.

• RPM and G-force selected based on fabric strength and machine capacity.

Precautions:

• Balance loads to avoid mechanical damage; delicate garments require lower G-force.

13. Drying

Purpose: Bring fabric to specified final moisture content for shipment or next processing step while avoiding thermal damage or shrinkage.

Dryer types: Tumble (batch), continuous conveyor/through-feed, stenter frames (with heat-setting for synthetic blends), infrared or air-impingement dryers.

Parameters:

• Temperature: depends on composition — cotton can tolerate higher temperatures (up to 120–140 °C air temp in stenter), polyester blends require controlled heat to prevent melting/thermal set.

• Time/airflow: adjusted to achieve target moisture content (2–6% final for fully dry product or higher if further finishing required).

• Tensioning in stenter for width control and heat setting.

Control points:

• Avoid over-drying (loss of tensile strength, surface yellowing).

• Use inline moisture sensors for endpoint control.

14. Final inspection, testing & packing

QC checklist:

• Visual check for shades, stains, uniformity.

• Whiteness / shade measured with spectrophotometer against standard.

• Fastness tests (wash, rub, light) for dyed/tinted batches.

• Dimensional checks (shrinkage), GSM validation.

• Record batch sheet, parameters, and attach QC tags.

Packing: Use moisture barrier if hydroscopic; avoid stacking while hot or humid to prevent mildew.

15. Environmental management & effluent treatment

Main concerns: COD/BOD from detergents & organics, peroxide residues, salts (from dyeing), color from unfixed dyes, high/low pH.

Key elements:

• Primary treatment: screening, equalization tanks.

• Chemical treatment: pH neutralization, coagulation/flocculation to remove suspended solids and dye aggregates where applicable.

• Biological treatment: activated sludge for biodegradable organics (detergents) after chemical pre-treatment.

• Tertiary treatment: filtration, activated carbon, membrane filtration (RO) where water reuse is targeted.

• Sludge handling: safe disposal or drying & disposal per regulation.

Water saving: Counter-current rinsing, reuse of rinse water after filtration, and optimized liquor ratios.

16. Safety, storage & handling

• Hydrogen peroxide: oxidizer—store in cool, ventilated area away from organics and metals; use PPE and splash goggles.

• Alkalis / acids: corrosive—have eyewash stations, spill kits.

• Enzymes: potential respiratory sensitizers—use masks and avoid aerosolization.

• Training: SOPs for chemical spills, first aid, and machine safety.

• Fire & lint control: dryers generate lint—frequent cleaning and spark arrestors.

17. Troubleshooting (common problems & fixes)

• Uneven desizing: misidentified sizing — verify and adjust enzyme/chemical type or mechanical action.

• Patchy bleaching / yellowing: metal ion contamination or peroxide degradation — add chelants, check peroxide quality, adjust stabilizers; neutralize residual peroxide properly.

• Poor dye fixation (tint fading in wash): insufficient alkali for reactive dye fixation or improper time/temperature — reprocess small batch to test re-fixation if possible.

• High COD in effluent: overuse of detergents or poor biodegradability — switch to biodegradable surfactants and optimize dosing.

• Excessive shrinkage or strength loss: over-bleaching/over-exposure to oxidants or high drying temperatures — reduce peroxide concentration/time or lower dryer temperature.

18. Process optimization & automation suggestions

• PLC & SCADA automation: pH, temperature, dosing, and timing automated for repeatability and logging.

• Counter-current rinsing & water recovery: reduces water use and effluent.

• Enzyme optimization: lower temp enzyme systems can reduce energy consumption and fiber damage.

• Inline sensors: conductivity, turbidity, moisture for real-time control.

• Batch records & KPI tracking: keep logs of chemical use/kg, water L/kg, energy kWh/kg, and rework % to measure improvement.

19. Example batch recipes (illustrative — lab-trial before scale)

Assumptions: 100 kg cotton greige in a jet or jigger style batch line. Adjust proportionally.

1. Desize (enzymatic):

   • α-Amylase: 0.3 g/L (lab determine)

   • Non-ionic wetting agent: 1.0 g/L

   • Temp: 55 °C

   • Time: 45 min

   • Liquor ratio: 1:6

2. Rinse: 2 × 10 min cold/warm

3. Bleach (H₂O₂):

   • H₂O₂: 4.0 g/L

   • Sodium silicate (stabilizer/buffer): 1.5 g/L

   • Chelant (sequestering agent): 1.0 g/L

   • Alkali (if required to reach pH 10): adjust with soda ash carefully

   • Temp: 60–70 °C

   • Time: 20 min

4. Neutralize:

   • Acetic acid to pH 5.5

   • If residual peroxide detected → small dose sodium bisulfite per titration

5. Detergent wash:

   • Non-ionic detergent 2 g/L, 40–50 °C, 20 min

6. Rinse until conductivity/pH acceptable

7. Tinting (optional low shade reactive):

   • Reactive dye: 0.2–0.5% owf (on weight of fabric)

   • Salt (exhaust): 20–50 g/L depending on exhaust method

   • Temperature profile and alkali addition as per dye supplier (pad-batch or exhaust method)

8. Fixing (reactive):

   • Soda ash: to target pH 10–11

   • Hold 30–60 min at 40–60 °C

   • Soaping: hot detergent wash to remove hydrolyzed dye

9. Softener:

   • Silicone softener: 6–8 g/L, 30–40 °C, 10–15 min

10. Hydro & Dry: target residual moisture and dry to spec.

Important: These numbers are starting points. Always validate on a lab or pilot scale and consult chemical suppliers for exact dosing and compatibility.

20. Suggested SOP template (for a single batch)

1. Pre-check: fabric weight/GSM, machine status, chemicals & PPE.

2. Desize: load, set temp/pH/time, add enzyme at specified time, monitor.

3. Rinse: perform two rinses, check conductivity.

4. Bleach: prepare peroxide bath, add stabilizer/chelants, ramp temp, monitor peroxide residual.

5. Neutralize: slowly add acid to target pH, measure.

6. Clean/soaping: add detergent, maintain temp/time.

7. Rinse: measure final pH & conductivity.

8. Tinting: prepare dye bath, apply/pad, exhaust/fix as required.

9. Fixing: apply alkali or heat, hold, then soaping.

10. pH adjust: to final spec.

11. Softener: apply & rinse if required.

12. Hydro-extract & Dry.

13. QC: shade, whiteness, fastness, shrinkage tests.

14. Log all parameter readings in batch sheet.

Closing notes

This document provides a robust, practical blueprint of a wet-washing line using the steps you specified. The single most important themes for success are:

• Know your substrate (fiber content, sizing type, prior finishes).

• Control pH, temperature, and time precisely at every step.

• Test on small scale before implementing full production changes.

• Monitor effluent & operate within environmental laws; invest in ETP and water reuse where viable.

• Keep detailed batch records for traceability and continual improvement.

• Wet Process Recipe For Bulk