Lesson 1Pretreatment steps for 100% cotton: desizing, scouring, bleaching and typical process rangesOutlines pretreatment of 100% cotton, including desizing, scouring, and bleaching. Discusses process ranges, key parameters, and how uniform pretreatment supports level dyeing and steady shade on cotton.
Desizing methods and enzyme versus oxidative routesScouring chemistry, alkali dosage and temperatureBleaching systems, stabilizers and whiteness targetsRinsing and neutralization after pretreatmentImpact of pretreatment quality on dyeing behaviorLesson 2Batch sequencing, dye lot scheduling and best practices to minimize re-dyeing and contaminationCovers planning of dye lots, batch sequencing, and scheduling to cut re-dyeing, contamination, and shade changes. Stresses machine loading, colour grouping, and talk between planning and dye house.
Lot size, fabric grouping and machine loadingDark-to-light and sensitive shade sequencingHandling re-dye lots and partial batch correctionsCommunication between planning and dye houseDocumentation and traceability of each dye lotLesson 3Dyeing methods: batch dyeing (jet, jigger), continuous dyeing, and pad-steam; process choices for knit and woven fabricsCompares batch and continuous dyeing methods for knits and wovens, including jet, jigger, pad-dry, and pad-steam. Discusses process choice, output, shade control, and fabric quality needs.
Jet dyeing principles and settings for knitsJigger dyeing control for woven fabricsPad-dry and pad-steam continuous dyeing linesProcess selection for fabric type and shade depthEnergy, water use and productivity comparisonLesson 4Reactive dye chemistry fundamentals and common recipes for cotton dyeingIntroduces reactive dye chemistry on cotton, including dye–fibre bonding, hydrolysis, and fixation. Shows common dye types, reaction ways, and standard recipes for light, medium, and dark shades on 100% cotton.
Reactive dye classes and functional groupsCellulose structure and reactive dye bondingHydrolysis, fixation and unfixed dye behaviorStandard light, medium and dark shade recipesAlkali selection for cold and hot brand dyesLesson 5Key process parameters to control: liquour ratio, pH, temperature profiles, time, salt and alkali dosingLooks at critical wet processing parameters and how liquor ratio, pH, temperature path, time, and salt or alkali dosing work to control dye uptake, levelness, and steadiness in cotton dyeing.
Effect of liquor ratio on dye uptake and levelnesspH control for reactive dye fixation and stabilityTemperature profiles and heating rate optimizationTime control, holding periods and migration balanceSalt and alkali dosing curves and addition methodsLesson 6Dye bath management and recipe control to prevent lot-to-lot shade variationExplains how to set up, charge, and watch dye baths to avoid shade changes. Focuses on recipe checks, addition order, bath reuse, and in-bath fixes to keep steady shades between lots.
Recipe sheet verification and raw material checksSalt and alkali addition sequence and timingBath reuse, topping up and correction limitsIn-bath shade checks and on-line adjustmentsCleaning protocols to avoid cross contaminationLesson 7Auxiliaries affecting shade and pilling (sequesterants, levelling agents, dispersing agents, softeners)Covers roles of sequestering, levelling, dispersing agents, and softeners in controlling shade and pilling. Discusses choice criteria, dosage, and fit with reactive dyes and pretreatment remains in cotton processing.
Sequestering agents and water hardness controlLeveling agents for uniform dye distributionDispersing agents to prevent particle aggregationCationic and silicone softeners and handle effectsAuxiliary compatibility and foaming considerationsLesson 8Washing cycles and aftertreatments that influence color fastness and pillingDetails washing-off stages and aftertreatments that remove loose dye, boost colour fastness, and cut pilling. Stresses sequence design, water quality, and chemical choice for lasting, low-pilling dyed cotton fabrics.
Soaping stages for reactive dye washing-offRinsing efficiency, water quality and temperatureSoaping agents and chelants for unfixed dye removalAftertreatments to improve wet and rubbing fastnessMechanical and chemical approaches to reduce pillingLesson 9Sampling and spectrophotometric shade evaluation: delta E, standard illuminants, illuminant/observer settings, and tolerance limitsDescribes sampling steps and spectrophotometric shade checks. Covers delta E calculations, standard illuminants, observer settings, and tolerance limits used to pass or fail production dye lots.
Bulk and lab sampling procedures for dye lotsInstrument calibration and standardization stepsCIELAB coordinates and delta E calculationsChoice of illuminant and observer combinationsSetting and managing commercial shade tolerancesLesson 10Common causes of shade variation (uneven dye exhaustion, bad liquor distribution, temperature gradients, mismatched recipe or water quality)Looks at usual causes of shade changes, including uneven exhaustion, liquor spread issues, temperature shifts, recipe errors, and water quality. Gives diagnostic ways and fixes for mills.
Uneven dye exhaustion and migration problemsPoor liquor circulation and fabric loading issuesTemperature gradients and sensor inaccuraciesRecipe, weighing and dispensing mistakesWater quality, hardness and contaminant effects
