In Textile Manufacturing

In textile manufacturing, finishing refers to any process performed on yarn or fabric after weaving to improve the look, performance, or "hand" (feel) of the finished textile.[1] Some finishing techniques, such as fulling, have been in use with hand-weaving for centuries; others such as mercerization are by-products of the Industrial Revolution. Type of fabric finishing include: • • • • • • • • • • •

Bleachis ng to remove color Calendaring Dyeing to add color Fulling or waulking to add weight and density Mercerizing Pressing Printing to add color and pattern Scouring (washing with detergents, alkaline solutions, or enzymes to remove foreign matter) Shearing or singeing to smooth the fabric Watering to add moiré patterns Weighting silk with metallic salts to add weight and improve hang

Textile Finishing Finishing is the final series of operations that produces finished textile fabric from greige goods. Finishing operations are predominantly wet operations requiring large amounts of thermal energy for water heating and drying. Woven greige goods require some additional steps prior to dyeing, as compared to knit goods. As the first step in finishing woven goods, singeing burns protruding fibers by passing the fabric over an open flame or heated plates to produce a cleaner fabric and enhance future operations. Hot exhaust air is produced. Sizes and other ingredients added during slashing in the weaving mill are removed in the desizing operation by washing them in a detergent solution at temperatures up to 200°F and then rinsing them with fresh water. The process produces a wastewater stream of 100 to 120°F. Scouring is another washing process using steam and detergents to remove oils and mineral material. The scouring can be done by batch in pressurized vessels known as kiers or on a continuous basis. In either case, high temperatures, to 250°F, and long retention times, up to 12 hours, are used to ensure thorough saturation and cleaning. Finally, the fabric is rinsed. A waste stream of warm, contaminated water is produced. Next, the fabric is bleached, washed, and rinsed several times to achieve uniformity and improve its ability to absorb dyestuffs later in the finishing operation. Contaminated, warm wastewater is produced.

Mercerizing is an optional step and consists of a caustic spray, tensioning, water rinse, water wash, acid dip, and final water wash, and produces a warm wastewater stream. For the drying step, conventional steam-heated drying cans arranged in sequence are most usually used. Finishing is the final wet process wherein size and/or other ingredients are applied to the fabric to provide particular characteristics, such as stiffness, water proofing, etc. The fabric is dried and finally heat cured with a direct flame on a tenter frame to bring it to its final dimensions. Large quantities of hot exhaust gas in the 200°F range are produced. The woven fabric is now ready for dyeing. Knit goods do not require desizing and bleaching. The finishing process requires only scouring to thoroughly clean the goods prior to dyeing. As with woven fabric, the step involves hot water washes and rinsing, and produces warm, contaminated waste water.

Bleach From Wikipedia, the free encyclopedia

Jump to: navigation, search This article is about the chemical whitener. For the media franchise, see Bleach (manga). For other uses, see Bleach (disambiguation).

Commercial chlorine bleach

A bleach is a chemical that removes color or whitens, often via oxidation. Common chemical bleaches include household "chlorine bleach", a solution of approximately 3-6% sodium hypochlorite (NaClO), and "oxygen bleach", which contains hydrogen peroxide or a peroxide-releasing compound such as sodium perborate or sodium percarbonate. To bleach something is to apply bleach, sometimes as a preliminary step in the process of dyeing. Bleaching powder is calcium hypochlorite. Many bleaches have strong bactericidal properties, and are used for disinfecting and sterilizing. Most bleaches are hazardous, and should be used with care. Dyeing is the process of imparting colours to a textile material in loose fibre, yarn, cloth or garment form by treatment with a dye.

Fulling or tucking or walking ("waulking" in Scotland) is a step in woollen clothmaking which involves the cleansing of cloth (particularly wool) to get rid of oils, dirt, and other impurities, and thickening it. The worker who does the job is a fuller, tucker or walker. Despite suggestions to the contrary,[1] these processes are essentially identical.

Process Fulling involves two processes - scouring and milling (thickening). These are followed by stretching the cloth on great frames known as tenters and held onto those frames by tenterhooks. It is from this process that we derive the phrase being on tenterhooks as meaning to be held in suspense. The area where the tenters were erected was known as a tenterground. Originally, this was literally pounding the cloth with the fuller's feet (whence the description of them as 'walkers'), or with his hands or a club. However, from the medieval period, it was often carried out in a water mill.

[edit] Scouring In Roman times, fulling was conducted by slaves standing ankle deep in tubs of human urine and cloth. Urine was so important to the fulling business that urine was taxed. Urine (known as 'wash') was a source of ammonium salts, and assisted in cleansing the cloth. By the medieval period, fuller's earth had been introduced. This is a soft clay-like material occurring in nature as an impure hydrous aluminium silicate. This seems to have been used in conjunction with 'wash'. More recently, soap has been used.

[edit] Thickening The second function of fulling was to thicken the cloth, by matting the fibres together to give it strength. This was vital in the case of woollens, made from short staple wool, but not worsteds made from long staple wool. At this stage, the liquid used was water, thus rinsing out the foul smelling liquor used during cleansing.

[edit] Fulling mills

A fulling mill from Georg Andreas Böckler's Theatrum Machinarum Novum, 1661 From the medieval period, the fulling of cloth was often undertaken in a water mill, known as a fulling mill (also as walk mills or tuck mills). In Wales, a fulling mill is a pandy. In these, the cloth was beaten with wooden hammers, known as fulling stocks. Fulling stocks were of two kinds, falling stocks (operating vertically), used only for scouring, and driving or hanging stocks. In both cases the machinery was operated by cams on the shaft of a waterwheel or on a tappet wheel, which lifted the hammer.

Driving stocks were pivotted so that the 'foot' (the head of the hammer) struck the cloth almost horizontally. The stock had a tub holding the liquor and cloth. This was somewhat rounded on the side away from the hammer, so that the cloth gradually turned, ensuring that all parts of it were milled evenly. However, the cloth was taken out about every two hours to undo plaits and wrinkles. The 'foot' was somewhat triangular in shape, with notches to assist the turning of the cloth. Mercerization is a treatment for cotton fabric and thread that gives fabric a lustrous appearance. The process is applied to materials like cotton or hemp. The process was devised in 1844 by John Mercer of Great Harwood, Lancashire, England, who treated cotton fibres with sodium hydroxide. The treatment caused the fibres to swell, which in Mercer's version of the process shrunk the overall fabric size and made it stronger and easier to dye. The process did not become popular, however, until H. A. Lowe improved it into its modern form in 1890. By holding the cotton during treatment to prevent it from shrinking, Lowe found that the fibre gained a lustrous appearance.[1][2]

Spool of a 2-ply mercerized cotton thread with a polyester core. Individual staples can be seen in close up view. The modern production method for mercerized cotton, also known as pearl or pearle cotton, gives cotton thread (or cotton-covered thread with a polyester core) a sodium hydroxide bath that is then neutralized with an acid bath. This treatment increases luster, strength, affinity to dye, resistance to mildew, but also increases affinity to lint. Cotton with long staple fiber lengths responds best to mercerization. Mercerized thread is commonly used to produce fine crochet, and also to sew fursuits. Textile printing is the process of applying colour to fabric in definite patterns or designs. In properly printed fabrics the colour is bonded with the fiber, so as to resist washing and friction. Textile printing is related to dyeing but, whereas in dyeing proper the whole fabric is uniformly covered with one colour, in printing one or more colours are applied to it in certain parts only, and in sharply defined patterns. In printing, wooden blocks, stencils, engraved plates, rollers, or silkscreens are used to place colours on the fabric. Colourants used in printing contain dyes thickened to prevent the colour from spreading by capillary attraction beyond the limits of the pattern or design.

Traditional textile printing techniques may be broadly categorised into four styles: •

• •

•

Direct printing, in which colourants containing dyes, thickeners, and the mordants or substances necessary for fixing the colour on the cloth are printed in the desired pattern. The printing of a mordant in the desired pattern prior to dyeing cloth; the color adheres only where the mordant was printed. Resist dyeing, in which a wax or other substance is printed onto fabric which is subsequently dyed. The waxed areas do not accept the dye, leaving uncoloured patterns against a coloured ground. Discharge printing, in which a bleaching agent is printed onto previously dyed fabrics to remove some or all of the colour.

Resist and discharge techniques were particularly fashionable in the 19th century, as were combination techniques in which indigo resist was used to create blue backgrounds prior to block-printing of other colours.[1] Most modern industrialised printing uses direct printing techniques.