Scouring (textiles)

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Women washing clothes Splendor Solis - Traite d'Alchimie - Femmes lavant le linge.jpg
Women washing clothes

Scouring is a preparatory treatment of certain textile materials. Scouring removes soluble and insoluble impurities found in textiles as natural, added and adventitious impurities, for example, oils, waxes, fats, vegetable matter, as well as dirt. Removing these contaminants through scouring prepares the textiles for subsequent processes such as bleaching and dyeing. [1] : 74–75  Though a general term, "scouring" is most often used for wool. In cotton, it is synonymously called "boiling out", and in silk, and "boiling off". [2] : 1  [3] [4] [5] : 78 

Contents

Purpose of scouring

Scouring is an essential pre-treatment for the subsequent finishing stages that include bleaching, dyeing, and printing. [6] : 399  Raw and unfinished textiles contain a significant amount of impurities, both natural and foreign. It is necessary to eliminate these impurities to make the products ready for later steps in textile manufacturing. [2] : 1  For instance, fatty substances and waxy matters are the major barriers in the hydrophilicity of the natural fibers. Absorbency helps the penetration of chemicals in the stages such as dyeing and printing or finishing of the textiles. [7] These fats and waxy substances are converted into soluble salts with the help of alkali. [8] This treatment is called Saponification. [9]

Impurities

Foreign matter in addition to fiber is known as impurities. Textile fibers contain many types of impurities. e.g.:

The impurities in different natural fibers
Fiber typeImpurities in %ageSource
Wool 40-50 [5] : 78 
Cotton 10 [13]
Silk 22-30 [14]

Etymology, and history

Detail of engraving showing Scotswomen singing a waulking song while walking or fulling cloth, 1772 (from Pennant's Tour). Waulking 18th century engraving.jpg
Detail of engraving showing Scotswomen singing a waulking song while walking or fulling cloth, 1772 (from Pennant's Tour).

Etymology

The term "scouring" refers to the "act of cleaning with a rubbing action". [15]

History

Textile manufacturing was once an everyday household activity. [16] In Europe, women were often involved in textile manufacturing. They used to spin, weave, process, and finish the products they needed at home. [17] [18] [19] [ relevant? ] In the pre-industrial era, scouring (wool scouring) was a part of the fulling process of cloth making, in which the cloths were cleaned, and then milled (a thickening process). Fulling used to be done by pounding the woolen cloth with a club, or by the fuller's feet or hands. This process was associated with waulking songs, which were sung by women in the Scottish Gaelic tradition to set the pace. [20] [21] [22] [23]

Earliest scouring agents

Scouring agents are the cleaning agents that remove the impurities from the textiles during the scouring process. While these are now industrially-produced, scouring agents were once produced locally; lant or stale urine and lixivium, a solution of alkaline salts extracted from wood ashes, were among the earliest scouring agents. Lant, which contains ammonium carbonate, was used to scour the wool. [24] [2] : 9 

Wool scouring

Wool, before and after scouring CSIRO ScienceImage 11160 Siroscour.jpg
Wool, before and after scouring

The removal of lanolin, vegetable materials and other wool contaminants before use is an example of wool scouring. [25] [26] Wool scouring is the next process after the woollen fleece of a sheep is cut off. [27] Raw wool is also known as ''Greasy wool.''

"Grease" or "yolk'' is a combined form of dried sweat, oil and fatty matter. [28] Lanolin is the major component (5-25%) of raw wool which is a waxy substance secreted by the sebaceous glands of wool-bearing animals. [29] Greasy matter varies by breed. [2] : 13  Following the cleaning process, the wool fibers possess a chemical composition of keratin. [30] [5] : 1 

Impurities in wool

The impurities in wool [5] : 6 
Type of impurityIn Merino, %ageIn Crossbreed, in %age
Dirt or soil198
Grease1611
Suint68

Process

Three steps comprise the complete cleaning process for wool: steeping, scouring, and rinsing. [31]

Steeping

Potash and wool fat are two beneficial substances among the contaminants in wool, necessitating the development of specific cleaning techniques capable of recovering these compounds. Steeping is an alternative scouring process, In steeping system, scouring entails in parts. Wool steeping is carried out in stages such as immersing it in lukewarm water for many hours. [32] [33] When the wool includes only a little amount of yolk, the steeping method for recovering the yolk can be skipped. [34]

Scouring treatment

Scouring is the process of cleaning wool that makes it free from grease, perspiration residue ( "suint"), dead skin and dirt and vegetable matter present as impurities in the wool. It may consist of a simple boiling of wool in water or an industrial process of treating wool with alkalis and detergents (or soap and Sodium carbonate.) [35] [2] : 1  [36] Bath temperature is maintained (at 65 degree Celsius) to melt wool grease. [37] (Lanolin melts at a temperature of 38-44 °C.) [38]

The next treatment is carbonization, a treatment with strong acids that convert vegetable matter into carbon. [39]

Rinsing

Rinsing is the process of thoroughly washing the cleaned wool.

Alternative method

The alternative method is solvent scouring. [2] : 61 

Solvent method

Solvent scouring of wool replaces soap, detergent, and alkalies with a solvent liquid such as carbon tetrachloride, ether, petroleum naphtha, Chloroform, benzene, or carbon disulfide, etc. These liquids are capable of dissolving impurities but highly volatile and flammable. Hence, they need extra care in handling. [2] : 62 

Cotton scouring

High Pressure Blow-through Kier was used for Scouring EB1911 Bleaching - Fig. 4. --High Pressure Blow-through Kier.jpg
High Pressure Blow-through Kier was used for Scouring

In cotton, non-cellulosic substances such as waxes, lipids, pectic substances, organic acids contribute to around ten percent of the weight. [13] Cotton, in particular, has fewer impurities than wool. [5] : 102  Cotton scouring refers to removing impurities such as natural wax, pectins, and non-fibrous matter with a wetting agent and caustic soda. [8] : 25  [4] In comparison, alkaline boiling has no effect on cellulose. [5] : 102 

Impurities in cotton

Cotton Pectins, waxes, proteins, mineral compounds, and ash, etc.

The major impurities in cotton [10]
Type of impurity%age
Pectins 0.4-1.2
Wax 0.4-1.2
Others1.7

Methods

Continuous scouring

A continuous method takes place in an arrangement of J box. [3] : 19  [4]

Discontinuous scouring

In discontinuous method certain machines are used such as dyeing vessels, winches, jiggers and Kier. [3] : 19, 20  [8] : 51  [4]

Kier boiling

Kier is a large cylindrical vessel, upright, with egg shaped ends made of boilerplate that has a capacity of treating one to three tonnes of material at a time. [40]

Kier boiling and ''Boiling off'' is the scouring process that involves boiling the materials with the caustic solution in the Kier, which is an enclosed vessel, so that the fabric can boil under pressure. [41] [42] [43] Open kiers were also used with temperatures below 100 °C (at atmospheric pressure). [5] : 102 

Biotechnology

Biotechnology in textiles is the advanced way of processing, textiles, it contributes to numerous treatments of cellulosic materials such as desizing, denim washing, biopolishing, and scouring, etc. [44]

Scouring with enzymes

Enzymes are helpful in bio-singeing, bio-scouring and removing impurities from cotton, which is more environmentally friendly. [45] Biopolishing is an alternative method that is an enzymetic treatment to clean the surface of cellulosic fabrics or yarns. It is also named ''Biosingeing.'' [46] [47] Pectinase enzymes, breaks down pectin, a polysaccharide found in cellulosic materials such as cotton. [48]

Silk scouring

Silk is an animal fiber it consists 70–80% fibroin and 20–30% sericin (the gum coating the fibres). It carries impurities like dirt, oils, fats and sericin. The purpose of silk scouring is to remove the coloring matter and the gum that is a sticky substance which envelops the silk yarn. The process is also called ''degumming''. The gum contributes nearly 30 percent of the weight of unscoured silk threads. Silk is called ''boiled off'' when the gum is removed. The process includes the boiling the silk in a soap solution and rinsing it out. [49] [14]

Manmade material Scouring

Oil and dirt are the impurities in Synthetic materials. Certain oils and waxes are applied as lubricants during spinning or fabric manufacturing stages such as knitting or weaving. Mild detergents can remove the impurities effectively. [5] : 116 

Effluent of scouring

Effluent is waste water that is thrown away in the water bodies. Industrial wastewater contaminated with scouring residues is heavily contaminated and extremely polluted. [50] [5] : 78 

See also

Related Research Articles

<span class="mw-page-title-main">Wool</span> Textile fiber from the hair of sheep or other mammals

Wool is the textile fiber obtained from sheep and other mammals, especially goats, rabbits, and camelids. The term may also refer to inorganic materials, such as mineral wool and glass wool, that have properties similar to animal wool.

<span class="mw-page-title-main">Textile</span> Various fiber-based materials

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<span class="mw-page-title-main">Cellulose acetate</span> Organic compounds which are acetate esters of cellulose

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<span class="mw-page-title-main">Flannel</span> Soft woven fabric with a lightly napped surface

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<span class="mw-page-title-main">Mercerisation</span> Chemical treatment for cellulosic yarns

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<span class="mw-page-title-main">Textile manufacturing</span> The industry which produces textiles

Textile manufacturing is a major industry. It is largely based on the conversion of fibre into yarn, then yarn into fabric. These are then dyed or printed, fabricated into cloth which is then converted into useful goods such as clothing, household items, upholstery and various industrial products.

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The manufacture of textiles is one of the oldest of human technologies. To make textiles, the first requirement is a source of fiber from which a yarn can be made, primarily by spinning. The yarn is processed by knitting or weaving, which turns yarn into cloth. The machine used for weaving is the loom. For decoration, the process of colouring yarn or the finished material is dyeing. For more information of the various steps, see textile manufacturing.

<span class="mw-page-title-main">Textile bleaching</span> Textile wet process that improves whiteness by removing natural color

The textile bleaching is one of the steps in the textile manufacturing process. The objective of bleaching is to remove the natural color for the following steps such as dyeing or printing or to achieve full white. All raw textile materials, when they are in natural form, are known as 'greige' material. They have their natural color, odor and impurities that are not suited to clothing materials. Not only the natural impurities will remain in the greige material, but also the add-ons that were made during its cultivation, growth and manufacture in the form of pesticides, fungicides, worm killers, sizes, lubricants, etc. The removal of these natural coloring matters and add-ons during the previous state of manufacturing is called scouring and bleaching.

<span class="mw-page-title-main">Alpaca fiber</span> Natural fiber

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<span class="mw-page-title-main">Finishing (textiles)</span> Manufacturing process

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.

Textile manufacturing is one of the oldest human activities. The oldest known textiles date back to about 5000 B.C. In order to make textiles, the first requirement is a source of fibre from which a yarn can be made, primarily by spinning. The yarn is processed by knitting or weaving to create cloth. The machine used for weaving is the loom. Cloth is finished by what are described as wet process to become fabric. The fabric may be dyed, printed or decorated by embroidering with coloured yarns.

<span class="mw-page-title-main">Kier (industrial)</span> Rotating boiler or vat used in bleaching or scouring cotton fabric

A kier or keeve is a large circular boiler or vat used in bleaching or scouring cotton fabric. They were also used for processing paper pulp.

Wet Processing Engineering is one of the major streams in Textile Engineering or Textile manufacturing which refers to the engineering of textile chemical processes and associated applied science. The other three streams in textile engineering are yarn engineering, fabric engineering, and apparel engineering. The processes of this stream are involved or carried out in an aqueous stage. Hence, it is called a wet process which usually covers pre-treatment, dyeing, printing, and finishing.

Bourette is a silk fabric with bumps often blended with other yarns made of Bourette fibers. The name "Bourette" is from its constituting fiber. It has a rough surface incorporating multicolored threads and knots of spun silk. The fabric is made with silk bourette and wool or cotton yarn. Bourette is a lightweight single cloth with a rough, knotty, and uneven surface.

<span class="mw-page-title-main">Greige goods</span> Woven or knitted fabrics which are not yet dyed or finished.

Greige goods are loom state woven fabrics, or unprocessed knitted fabrics. Greige goods undergo many subsequent processes, for instance, dyeing, printing, bleaching, and finishing, prior to further converting to finished goods such as clothing, or other textile products. "Grey fabrics" is another term to refer to unfinished woven or knitted fabrics.

<span class="mw-page-title-main">Hand feel</span> Feel of the fabrics to the skin or hand

Hand feel is the property of fabrics related to the touch that expresses sensory comfort. It refers to the way fabrics feel against the skin or in the hand and conveys information about the cloth's softness and smoothness. Hand feel is an estimated and subjective property of different fabrics, but nowadays, hand feel could be measured and assessed statistically.

Singeing is a preparation method of textiles; it is applied more commonly to woven textiles and cotton yarns where a clean surface is essential. 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 or to the heated plates to burn the protruding fibers. It is also called "gassing."

<span class="mw-page-title-main">Grassing (textiles)</span> Old method of bleaching

Grassing is one of the oldest methods of bleaching textile goods. The grassing method has been long been used in Europe to bleach linen and cotton based fabrics.

A blend is a mixture of two or more fibers. In yarn spinning, different compositions, lengths, diameters, or colors may be combined to create a blend. Blended textiles are fabrics or yarns produced with a combination of two or more types of different fibers, or yarns to obtain desired traits and aesthetics. Blending is possible at various stages of textile manufacturing. The term, blend, refers to spun fibers or a fabric composed of such fibers. There are several synonymous terms: a combination yarn is made up of two strands of different fibers twisted together to form a ply; a mixture or mixed cloth refers to blended cloths in which different types of yarns are used in warp and weft sides.

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