Unit Operations


Is the preliminary process in spun yarn manufacture. The fibres are separated, distributed, equalized, and formed into a thin web and condensed into a continuous, untwisted strand of fibres called a sliver. This process also removes impurities and a certain amount of short, broken or immature fibres.


Is the process of making yarn from fibres by a combined drawing out and twisting operation or from filament tow by the combination of cutting/breaking with drafting and twisting in a single series of operations.

Slashing (Sizing)

The yarn is run through a size solution and then dried so that it has the strength and stiffness required to withstand the abrasion and friction generated in the weaving operation.


Is the process of interlacing two yarns of similar materials so that they cross each other at right angles to produce woven fabric.


Is the process of constructing fabric by an interlocking series of loops of one or more yarns.


Is the process of making carpets and involves a wide multiple-machine needle process that sews pile yarns to a broad fabric backing.


Removes the sizing compounds applied to yarns to impart tensile strength. The starch sizing compounds are solubilized with alkali, acid or enzyme, and the fabric is washed thoroughly. Alkaline desizing utilizes a weak alkaline solution to facilitate size removal, while acid desizing employs a dilute acid solution to hydrolyze the size and render it water soluble. Enzyme desizing utilizes enzymes to decompose size. After solubilizing the size, the fabric is rinsed clean.


Removes natural and acquired impurities from fibres and fabric. Synthetic fibres require less scouring than does cotton or wool. Scouring agents include detergents, soaps, and various assisting agents, such as alkalis, wetting agents, defoamers, and lubricants. After scouring, the goods are thoroughly rinsed (or washed) to remove excess agents.

Wool Carbonizing

Removes burrs and other vegetable matter from loose wool or woven fabric goods. The process consists of acid impregnation, baking and mechanical agitation. A dilute solution of sulfuric acid is used to degrade cellulosic impurities to hydrocellulose without damaging the wool. The excess acid is squeezed from the wool and the wool is baked to oxidize the contaminants to gases and a solid carbon residue. The material then passes through pressure rollers to crush the solid residue and into a mechanical agitator to shake loose the crushed material. The acid content in the material remains high after agitation, requiring neutralization and rinsing before further processing.


Fulling involves mechanical working in a bath of detergent and water and imparts a felt quality to the wool.


Bleaching is performed to whiten (remove coloring) the fabric to a high degree. It is a common process used to whiten cotton, wool and some synthetic fibres by removing the natural coloring. It is usually performed after scouring and prior to dyeing or printing. Bleaching chemicals include sodium hypochlorite, hydrogen peroxide, and sodium perborate, as well as optical brighteners. Batch bleaching is done in dyers (continuous processes use J-boxes) where fabric is tacked for a given period to allow the chemical to work before goods are withdrawn from the bottom of the box. Bleaching is followed by thorough rinsing.


Mercerizing is only applied to 100% cotton fabrics and sewing threads. It is used to improve strength, luster and dye affinity, albeit at the expense of extensibility. It is accomplished by the application of a cold solution of sodium hydroxide, causing the fibres to swell and adopt a circular cross-section. The alkali is then removed by an acid wash.


Can be performed in the stock, yarn or fabric state, and single or multiple-fibre types can be dyed. Multiple-fibre may require multiple or sequential steps.

Stock dyeing is performed before the fibre is converted to the yarn state and can be a batch or continuous process. Yarn dyeing is performed on yarns used for woven goods, knit goods, and carpets. Usual methods include skein, package, and space dyeing.

Fabric dyeing is the most common method in use today because it can be continuous or semicontinuous, as well as a batch process. Methods employed include becks (winch), jet, jig, beam, and continuous range.

The various types of dyes used are classified according to the method of application. A listing of the more prominent dyes follows:


Printing is similar to dyeing, except that print color is applied to specific areas of the cloth. Dyes and auxiliaries are similar to those used in fabric dyeing; however, the color application techniques are quite different. Textiles are usually wet-printed by roller, rotary screen or flatbed screen printing methods.


The primary purpose of the finishing process is to alter properties affecting the care, comfort, durability, environmental resistance, aesthetic value, and human safety associated with the fabric. Finishes can be applied, for example, to make a fabric wrinkle resistant, crease retentive, water repellant, flame resistant, mothproof, mildew resistant, and/or stain resistant. Finishes include a very large and diverse group of chemicals ranging from antistatic to shrink-resistant finishes. In wet-finishing, the sequence of steps typically includes chemical finish application together with mechanical techniques, the advantages of the latter being improved feel, strength and abrasion resistance and lower chemical consumption and waste [2]. Finishing is usually a continuous process that produces little or no wastewater [6].