Finishing (textiles)
In textile manufacturing, finishing refers to the processes that convert the woven or knitted cloth into a usable material and more specifically to any process performed after dyeing the yarn or fabric to improve the look, performance, or "hand" (feel) of the finish textile or clothing. The precise meaning depends on context. Fabric after leaving the loom or knitting machine is not readily useable. Called grey cloth at this stage, it contains natural and added impurities. Sometimes it is also processed at fiber or yarn stages of textile manufacturing. Grey fiber or yarn or fabric goes through a  series of processes such as wet processing and finishing. Finishing is a broad range of physical and chemical processes/treatments that complete one stage of textile manufacturing and may be preparing for the next step. And makes the product more receptive to the next stage of manufacturing. Finishing adds value to the product and makes it more attractive, useful, and functional for the end-user. Improving surface feel, aesthetics, and addition of advanced chemical finishes are some examples of textile finishing. Some finishing techniques such as bleaching and dyeing are applied to yarn before it is woven while others are  applied to the grey cloth directly after it is woven or knitted. Some finishing techniques, such as fulling, became outdated with the industrial revolution while others, such as mercerisation, are developments following the Industrial Revolution. Introduction. In order to impart the required functional properties to the fiber or fabric, it is customary to subject the material to different types of physical and chemical treatments. For example, wash and wear finish for a cotton fabric is necessary to make it crease-free or wrinkle-free. In a similar way, mercerising, singeing, flame retardant, water repellent, waterproof, anti-static and peach finishing  achieve various fabric properties desired by consumers. The use of 100% synthetic textiles has increased considerably since the development of textured yarns made of filaments and the growing production of knit goods. The use of open weave has enabled the production of lighter, breathable, fabrics to ensure better wearing comfort. The properties of petroleum-based synthetic fibers, most important among them being polyamide, polyester and polyacrylonitrile, are essentially different from those of natural cellulosic and protein/ wool fibers. Hence the sequence of finishing operations is likely to be different. While cellulosic fabrics require a resin finishing treatment to impart easy -care properties, synthetic fibers already exhibit these easy-care criteria and require only a heat setting operation. Finishing of cotton. Purification and preliminary processes. The grey cloth—woven cotton fabric in its loom-state—not only contains impurities, including warp size, but requires further treatment in order to develop its full textile potential. Furthermore, it may receive considerable added value by applying one or more finishing processes. Singeing. Singeing is a preparation method of textiles; it is applied more commonly to woven textiles and cotton yarns. Singeing in textiles is a mechanical treatment or finish to obtain a neat surface  of the fabric or less hairy yarn. In a singeing machine, the yarns or fabrics are exposed to direct flames to burn the protruding fibers of the textile materials. Hence, also called "gassing". Desizing. Depending on the size that has been used, the cloth may be steeped in a dilute acid and then rinsed, or enzymes may be used to break down the size. Scouring. Scouring is a chemical washing process carried out on cotton fabric to remove natural wax and non-fibrous impurities (e.g. the remains of seed fragments) from the fibres and any adventitious oil, soiling or dirt . Scouring was used to carry in iron vessels called kiers. The fabric was boiled in an alkali, which forms a soap with free fatty acids (saponification). A kier is usually enclosed, so the solution of sodium hydroxide can be boiled under pressure, excluding oxygen which would degrade the cellulose in the fibre. If the appropriate reagents are used, scouring will also remove size from the fabric although desizing often precedes scouring and is considered to be a separate process known as fabric preparation. Preparation and scouring are prerequisites to most of the other finishing processes. At this stage even the  most naturally white cotton fibres are yellowish, and bleaching, the next process, is required. Bleaching. Bleaching improves whiteness by removing natural coloration and remaining trace impurities from the cotton; the degree of bleaching necessary is determined by the required whiteness and absorbency. Cotton being a vegetable fibre will be bleached using an oxidizing agent, such as dilute sodium hypochlorite or dilute hydrogen peroxide. If the fabric is to be dyed a deep shade, then lower levels of bleaching are acceptable, for example. However, for white bed sheetings and medical applications, the highest levels of whiteness and absorbency are essential. Mercerising . A further possibility is mercerizing, during which the fabric is treated with a caustic soda solution to cause swelling of the fibres. This results in improved luster, strength, and dye affinity. Cotton is mercerized under tension, and all alkali must be washed out before the tension is released or shrinkage will take place. Mercerizing can take place directly on grey cloth, or after bleaching. Coloration. Color is a sensation caused when white light from a source such as the sun is reflected off a pigment on the surface. The pigment selectively reflects certain wavelengths of light while absorbing others. A  dye can be considered as a substance that can be fixed to a material that has these properties. The colour it reflects is defined by the structure of the molecule, and particularly the parts of the chromogen molecule called the chromophore group. There are two processes used to apply colour: Dyeing. Cotton is an absorbent fibre which responds readily to colouration processes. Dyeing is commonly carried out with an anionic direct dye by completely immersing the fabric (or yarn) in an aqueous dyebath according to a prescribed procedure. For improved fastness to washing, rubbing, and light, other dyes such as  vats and reactives are commonly used. These require more complex chemistry during processing and are thus more expensive to apply. Printing. Printing is the application of colour in the form of a paste or ink to the surface of a fabric, in a predetermined pattern. It may be considered as localised dyeing. Printing designs on to already dyed fabric is also possible. The common processes are block printing, roller printing and screen printing Finishing. Mechanical finishing. Mechanical finish refers to machine finishes such as embossing, heat setting, sanforizing, sheering, various, luster imparting, surface finishes, and glaze finishes. Raising. Another finishing  process is raising. During raising, the fabric surface is treated with sharp teeth to lift the surface fibres, thereby imparting hairiness, softness, and warmth, as in flannelette. Shearing. Shearing is a kind of mechanical finish in which the appearance of the fabric is enhanced by cutting the loops or raised surface to a uniform and even height. The machine may have a spiral blade similar to a grass cutting machine. A Shearing machine can cut the loop or the pile to a desired level. Peaching. Peaching is also a mechanical finish comparable to raising but very gentle. The peach effect  on fabrics is obtained by sanding the fabrics slightly; it imparts a protruded surface and soft feel. The peaching finish is also possible with certain chemicals or laundry abrasion. Calendering. Calendering is the third important mechanical process, in which the fabric is passed between heated rollers to generate smooth, polished or embossed effects depending on roller surface properties and relative speeds. Chemical finishing. Many other chemical treatments may be applied to cotton fabrics to produce low flammability, crease resist and other special effects. Shrinking. Mechanical shrinking (sometimes referred to as sanforizing), whereby the fabric is forced to shrink width and/or  lengthwise, creates a fabric in which any residual tendency to shrink after subsequent laundering is minimal.