Introduction
Textile printing is a familiar part of fabric production, whether the aim is a simple single-colour motif or a more complex multicoloured pattern. It is often described as a localised dyeing process, and it uses the same dyes or pigments with similar principles of application and colour fastness properties as textile dyeing. In practice, the colourant, print paste, and fixation route all influence the final result. Even when the printing style changes, the basic sequence usually stays the same.
Colourants Used in Textile Printing
Among the colourants available in dyeing, pigment is the most commonly used. Its advantages are easy to see. It is economical because it needs lower machine investment, gives good reproducibility, allows less difficulty in washing off, supports quick sampling, and offers a high production rate. It can also be applied on all fibres and their blends, provides a complete colour range, and is especially suitable for colour-resistant and discharge printing because of its inert chemical nature.
Pigment printing does have drawbacks. Its washing, rubbing, and dry-cleaning fastness properties are inferior, and the finished fabric usually has a harsh, hardened hand feel. Because of this, other dye classes are sometimes used to overcome the weakness of pigment. Still, not every dye class can be used in printing, since some have solubility difficulty, low colour yield, or poor print-paste stability. The suitable dye classes for different fibre types are reactive dyes for cotton and other cellulosic fibres, rayon, wool and other animal fibres, and silk; acid dyes for wool and other animal fibres, and silk; disperse dyes for polyester and acetate; and basic dyes for acrylic.
Typical Textile Printing Process
In spite of the different methods and styles of printing, the typical textile printing procedure usually follows six stages: preparation of ground colour, preparation of print paste, printing, drying, fixation, and washing off.
Preparation of Ground Colour
The printing process can be carried out on a bleached white ground or overprinted on a coloured ground. In the first case, the fabric needs a series of wet-processing steps such as desizing, scouring, and bleaching of the grey fabric. In the second case, the coloured ground may be produced by either a dyeing or printing process.
Preparation of Print Paste
Before printing can begin, the print paste of the required colour must be prepared. The basic components of print paste are dye or pigment, water, thickening agent, and suitable chemicals. Water is used to dissolve or disperse the dye, pigments, and chemicals, and it also helps regulate the overall viscosity of the print paste. The thickening agent is used to give the paste the desired viscosity so that the printed patterns have good sharpness and definition.
The most common thickening agents are starch and gum products, but they tend to form a hard gel after drying and should be removed afterwards to avoid a stiff handle. Emulsion thickener, a cream-like product made by high-speed stirring of a mixture of water and petroleum oil, may be used as a substitute or mixed with starch and gum to give a softer handle. Other thickening agents that may sometimes be used on particular occasions include starch derivatives, cellulose derivatives, alginates, and synthetic polymer thickeners. The function of adding chemicals is to assist dye solubility or pigment dispersion, dye fixation, and print paste stability.
Printing
The methods of printing can mainly be classified as roller printing, rotary-screen printing, and flatbed screen printing. For each production method, various techniques or types of prints can be applied.
Drying
After printing, the fabric may need to be dried to prevent smudging, or marking off, of the wet print. Drying may not be necessary if a dry-heat, hot-air baking fixation is applied immediately after printing.
Fixation
Fixation is normally done by either dry heat above 100°C or steaming. It is an important step that allows the absorbed dye or pigment molecules to penetrate and fix to the fibres. This stage is often underestimated in practice, yet it has a direct effect on the final print quality.
Washing Off
A washing-off process, with soaping and enough cold and hot water rinsing, is used to remove the unfixed dye, thickening agent, and residue chemicals. Special care, such as controlling the washing temperature and adding a suitable detergent, is taken during the process to prevent staining of the unprinted areas by unfixed dye in the wash liquid.
Conclusion
Textile printing process brings together the right colourant, the right paste, and the right finishing sequence to produce clear and durable patterns on fabric. Pigments remain popular because they are economical, versatile, and easy to handle, even though their fastness and hand feel can be weaker. Other dye classes are used where fibre type and print performance call for a better match. When ground preparation, paste preparation, printing, drying, fixation, and washing off are carried out in the correct order, the process becomes far more reliable. That is why careful control at every stage still matters so much in textile printing.
