Lesson 1Pretreatment steps for 100% cotton: desizing, scouring, bleaching and typical process rangesOutlines prep of pure cotton, including size removal, cleaning, and bleaching. Discusses process ranges, main settings, and how even prep supports level dyeing and steady colour 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 dye batches, order, and timing to cut re-dyeing, dirt, and colour shifts. Stresses machine load, colour groups, and talk between planning and dye area.
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 steady dyeing for knits and wovens, like jet, jigger, pad-dry, pad-steam. Discusses choice, output, colour control, and fabric quality points.
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 basics on cotton, like dye-fibre bond, hydrolysis, fixation. Shows usual dye types, reactions, and standard mixes for light, medium, dark on pure 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 key wet process settings and how liquor ratio, pH, temp path, time, salt or alkali add work to control dye take, evenness, 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, fill, and watch dye baths to avoid colour shifts. Focuses on recipe check, add order, bath reuse, and bath fixes for steady colours across batches.
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 helpers, and softeners in colour and pilling control. Discusses choice, dose, and fit with reactive dyes and prep remains in cotton work.
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 wash stages and aftertreats that remove loose dye, boost colour fastness, cut pilling. Stresses order design, water quality, chemical choice for lasting, low-pill dyed cotton.
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 sample ways and colour check with spectrophotometer. Covers delta E math, standard lights, observer settings, and limit points to pass or fail dye batches.
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 colour shift causes, like uneven dye use, liquor spread issues, temp differences, recipe errors, water quality. Gives check 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
