UPMSP Intermediate Dyeing Art key terms

The part of a dye molecule responsible for colour by absorbing certain wavelengths of visible light and reflecting others. It usually contains conjugated double bonds or aromatic rings that create the colour-producing electronic structure.

A chemical group attached to a chromophore that intensifies colour and helps the dye bind to fibres. Common auxochromes include hydroxyl (-OH), amino (-NH2), and sulfonic acid (-SO3H) groups, which also improve water solubility.

The attraction between a dye and a fibre that allows the dye to be absorbed directly from the dye bath without a mordant. High substantivity means the dye migrates readily onto the fibre and stays there.

The thermodynamic tendency of a dye to leave the dye liquor and enter the fibre phase. It is measured as the standard affinity and indicates how strongly the dye prefers the fibre over the solution.

The proportion of dye originally in the dye bath that has transferred onto the fibre at any given time, usually expressed as a percentage. Complete exhaustion means all dye has left the bath and fixed to the material.

The process by which dye molecules become permanently trapped within or chemically bonded to the fibre so they resist washing. Fixation follows exhaustion and may require steam, heat, or a chemical after-treatment.

The attribute of colour that distinguishes red from yellow, green, blue, and so on, independent of lightness or saturation. It is the name we give to the pure colour family on the colour wheel.

The lightness or darkness of a colour, ranging from black through grey to white. In dyeing, value is controlled by the concentration of dye and the amount of light the dyed fibre reflects.

The purity or intensity of a colour, showing how free it is from grey or white. A highly saturated dye produces a vivid shade, while a desaturated one appears muted or dull.

Two colours positioned opposite each other on the colour wheel, such as red and green or blue and orange. When mixed they neutralise each other to produce grey or brown, a principle used for shading and correction in dyeing.

A fibre composed of polymerised glucose units, such as cotton, linen, and viscose. Cellulose fibres are hydrophilic, burn like paper, and are dyed mainly with direct, reactive, vat, and azoic dyes.

A fibre made of amino acid chains, including wool and silk. Protein fibres contain amino and carboxyl groups that attract acid dyes and react with reactive dyes, and they are damaged by strong alkalis.

A manufactured fibre produced by dissolving a natural polymer and extruding it into filaments, for example viscose rayon from wood pulp. Its dyeing behaviour resembles cotton but it is weaker when wet.

A fibre made from petrochemical polymers, such as polyester, nylon, and acrylic. Synthetic fibres are hydrophobic, thermoplastic, and usually dyed with disperse dyes under high temperature or carrier conditions.

An anionic dye that dyes cellulose fibres directly from an aqueous bath with the help of electrolyte, without a mordant. Direct dyes are simple to apply but generally have moderate wash fastness unless after-treated.

A dye containing a reactive group that forms a covalent chemical bond with hydroxyl or amino groups in the fibre. This bond gives excellent wash fastness, but unfixed dye must be removed thoroughly to avoid poor fastness.

An insoluble dye that is reduced in an alkaline vat to a soluble leuco form, applied to the fibre, then oxidised back to its insoluble coloured form inside the fibre. Vat dyes give very high fastness, especially to washing and light.

An anionic dye applied to protein fibres such as wool and silk in an acidic bath. The acid protonates amino groups in the fibre, attracting the dye and forming ionic bonds that provide good colour fastness.

A cationic dye that bonds to anionic sites in fibres such as acrylic, wool, and silk. Basic dyes give bright, intense shades but generally have poor light fastness on cellulosic fibres unless mordanted.

A finely dispersed, water-insoluble dye used mainly for hydrophobic synthetic fibres like polyester. It dissolves into the fibre structure under heat, often with a carrier or at high temperature and pressure.

A dye formed inside the fibre by coupling a diazonium salt with a naphthol. The two components are applied separately, producing bright, deep shades with good wash fastness, especially on cotton.

The chemical reaction in which a primary aromatic amine is treated with nitrous acid to form a diazonium salt. In azoic dyeing, this salt is the reactive component that couples with naphthol inside the fibre to form the dye.

The reaction between a diazonium salt and a naphthol or other coupling component to form an azo dye. In azoic dyeing, coupling takes place within the fibre after the naphthol has been applied and the fabric is passed through the diazonium bath.

A metal salt, such as alum or iron sulphate, that binds to both fibre and dye, forming an insoluble colour lake inside the fibre. Mordants improve fastness and can shift the hue of natural and some synthetic dyes.

A chemical additive that promotes even distribution of dye across the fibre by slowing dye uptake or helping dye migrate. It reduces patchiness and is especially important in wool and nylon dyeing.

An assistant that slows the rate of dye absorption so the dye can penetrate evenly before fixing. Retarders are used in basic dyeing of acrylic and in some direct dye applications to prevent rapid, uneven strike.

A salt such as sodium chloride or sodium sulphate added to a dye bath to promote dye exhaustion onto cellulose fibres. It reduces the negative charge barrier between the anionic dye and the fibre surface.

A chemical that binds metal ions such as calcium, magnesium, and iron in hard water, preventing them from interfering with dyeing. It improves shade reproducibility and avoids metal-dye complexes that cause dulling or spotting.

A surfactant that lowers the surface tension of water so the dye liquor penetrates the fibre quickly and uniformly. Good wetting is essential for level dyeing, especially on tightly woven or naturally water-repellent fabrics.

A traditional Indian tie-dye technique in which small sections of cloth are pinched and tied tightly with thread before dyeing. The tied areas resist the dye and form patterns of small dots, often in bright colours.

A resist dyeing method in which melted wax is applied to cloth to block dye penetration. The wax is cracked or drawn to create patterns, and the process may be repeated with different colours before the wax is removed.

Any dyeing process in which parts of the fabric are protected from dye by a physical barrier such as wax, thread, or paste. The barrier is removed after dyeing to reveal the undyed or previously dyed pattern.

A resist technique where fabric is folded, twisted, or gathered and bound with string before dyeing. The bound areas resist dye and create circular, striped, or spiral patterns when the fabric is opened.

A hand printing method in which a carved wooden block is dipped in dye or pigment paste and stamped onto fabric. Repeated impressions build up a pattern, and registration must be accurate for multicolour designs.

The resistance of a dyed material to colour loss or transfer during washing, light exposure, rubbing, perspiration, and other conditions. It is graded against standard grey scales, with higher grades indicating better performance.

The ability of a dyed textile to retain its colour when washed, assessed by changes in shade and staining of adjacent fabrics. It depends on dye fixation and the strength of dye-fibre bonding.

The resistance of a dye to fading when exposed to sunlight or artificial light. It is tested by comparing the sample with blue wool standards and is important for apparel and furnishing fabrics.

A standard series of grey chips used to assess colour change and staining in fastness testing. The contrast between the tested sample and the original or adjacent fabric is matched to a numerical grade.

A dyeing machine in which fabric is passed repeatedly through a dye liquor between two rollers, with the batch wound onto one roller and then the other. It is used for open-width woven fabric and allows good penetration with low liquor ratio.

A rope dyeing machine in which fabric is circulated in rope form through a dye bath by a rotating winch reel. It is suitable for delicate fabrics and small batches but can cause creasing and rope marks.

A yarn dyeing method in which yarn is hung in loose loops (hanks) on sticks and immersed in the dye bath. It gives soft, lofty yarns and is common for wool and hand-knitting yarns.

A yarn dyeing method where yarn is wound onto perforated packages and dye liquor is forced through the package under pressure. It gives uniform penetration and is efficient for large batches of yarn.

A continuous dyeing method in which fabric is passed through a dye liquor and then squeezed between rollers to give a uniform pickup. The fabric is then fixed by steam, heat, or chemical treatment.

A measure of the acidity or alkalinity of a solution on a scale from 0 to 14. In dyeing, pH controls dye ionisation, fibre charge, and reaction rates, so it must be adjusted for each dye class.

A chemical system that resists changes in pH when acid or alkali is added. Buffers are used in dye baths to keep the pH stable so that dye uptake and shade reproducibility remain consistent.

A chemical such as sodium hydrosulphite that donates electrons and converts vat dyes to their soluble leuco form. It is essential in vat dyeing and must be controlled to avoid over-reduction or poor colour yield.

The process of converting the soluble leuco form of a vat dye back to its insoluble coloured form inside the fibre. It is usually carried out in air, water, or a chemical oxidising bath after dye application.

A printing method in which insoluble pigment particles are fixed to the fabric surface with a binder rather than absorbed into the fibre. It works on all fibre types and gives good light fastness but stiffer handle.

A film-forming polymer used in pigment printing to adhere pigment particles to the fabric surface. It must be flexible, wash-fast, and compatible with the thickener and other print paste ingredients.

A substance such as sodium alginate or starch that increases the viscosity of a print paste so it stays in place on the fabric. It controls sharpness of print and prevents colour bleeding during steaming.