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A newly constructed fabric as it comes from the mill is known as greige goods or gray goods. This does not imply that the fabric is gray in colour; it simply denotes any unfinished fabric. The goods must pass through various finishing processes to make it suitable for its intended end use. Finishes may change the appearance of the fabric, its texture , its serviceability and its durability.
The basic finishes are further classified into two classes,
Finishes that appeal to the eye
Finishes that appeal to the touch
Bleaching : If the cloth is to be finished as white or to be given surface ornamentation, all natural colours must be removed by bleaching. This is also necessary if discoloration or stains have occurred during the previous manufacturing process. Bleaching can be done in the yarn stage as well as in the constructed fabric. Suitable bleaching agents are used to remove the colour from the fabric namely oxidizing or reducing bleaches. Bleaching is done for the cotton, woolen and silk. Man-made fabrics do not need bleaching, as they are naturally white. The kind of chemical to be used depends upon the kind of textile fiber of which the fabrics is composed.
Mercerizing : Mercerizing is an important preparatory process for cotton fabric. It is also used in the finishing of linen. The process consists of holding the fabric in tension while treating it with a strong solution of sodium hydroxide at a temperature of 70 to 80 F. Mercerizing causes the flat, twisted, ribbon like cotton fiber to swell into a round shape and to contract in length. The fiber becomes much more lustrous than the original fiber, and its strength increased by 20%. Mercerizing is done to improve the dye pick up.
Shearing : Pile-weave fabrics and fabrics that have been napped are usually sheared to give an attractive smooth surface to the cloth. Shearing levels all surface irregularities caused by the plucking action in the napping process. On the other hand, patterns may also be cut into the pile fabrics by shearing to give a 'sculptured effect' of a design having high and low surface levels. Shearing is done by a machine which has rotating cylinders and helical blades. Its action resembles that of a lawn mover. After shearing, the fabric is automatically brushed to remove the sheared ends of the yarns.
Singeing : Singeing is one of the first essential preparatory processes that impart smooth finish to fabric. Singeing burns off lint, threads, fuzz and fiber ends and leave an even surface before the fabric passes through other finishing processes or a printing operation. Singeing is accomplished by passing a gray goods rapidly over gas flame, usually two burners to a side, at a speed of 100 to 250 yards (90-225m) per minute. After the cloth leaves the burners it is pulled through water and then it is dried.
Beetling : Beetling is a common finishing process for linen. The yarns are flattened by the impact of wooden mallets. This hammering actually closes the weave and gives the cloth a firm, flattened, lustrous appearance. All table linens under go this process, but dress linens are never beetled. Beetling differs from calendering.
Tentering : This process is applied at various stages of finishing. Usually, the fabric is wet when it is run into a tender. Drying and evening of the fabric width are the primary purpose of the tendering. The tender frame consists of two endless chains carried in rugged rails with a distance between them that can be adjusted. The chains are equipped with clips or pins, which grip the selvage of the fabric and carry into the heated housing where a blast of hot air removes any moisture. Pin frames are mostly used on woollen or knitted goods; clip frames are favored for cotton. The tiny holes or marks are sometimes noticeable in the selvages.
Calendering : Calendering is essentially an ironing process that adds sheen to the fabric. The method varies according to the type of finish desired. Calenders are heavy machines made up of at least two rolls. One is usually of chilled steel; the other, a softer material like wood, paper, cotton fiber, corn husks or combinations of cotton and corn husk. The rolls are supported in vertical frames. Plain rolling calenders may have as many as seven rolls, four steel rolls and three horn husk or cotton rolls. The steel rolls may be equipped to be heated by gas or steam. The textile material is passed through the calendering machine rapidly between the gap formed by the rollers. This is done at an average rate of 150 yards (135m) per minute, and under pressure of 40 to 60 tons (550-827 MPa); the goods are then wound up on the back of the machine.
Moire finishes : Attractive, lustrous wavy designs known as moir� can be produced by a process of minute surface embossing or pressing of a fabric with crenellated, or ridged, rollers. The best moir� results are obtained on fabrics that have rib effects in the filling. The pattern is imprinted on the raised filling yarns by rollers. The luster is formed by the divergent reflection of light on the impressed lines of the design.
Pressing : Mostly pressing method is used for wool fabrics to remove short hair fibers present on the surface of the fabric. This pressing method is similar to calendering.
Embossing : The process of producing raised figures or designs in relief on the surface of the fabrics by passing the cloth between heated engraved rollers is known as embossing. The process can be applied to the fabrics made of all types of fibers except the wool. To preserve the embossed finish of such fabrics, they should be washed in lukewarm water with a mild soap, never be bleached, and ironed on the wrong side while damp.
Crepe and Crinkled effect : Permanent crepe effects are obtained by using hard twisted yarns in the weaving process. Another method imprints a crinkled effect by means of engraved rollers, but the finish disappears in repeated washing. In another finishing method, caustic soda is impressed on the cotton fabric in the form of figures or stripes and the fabric is then washed. The part imprinted with the caustic soda shrinks, and the other part puckers.
A permanent crinkle may be obtained on a fabric that can melt, such as nylon. The fabric is put through a hot roller on which there are raised figurations. The contact of the fabric against the raised hot surface helps it to melt and pucker at these points.
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