Fabric Finishing Process

Main Fabric Finishing Techniques

It is the process of burning off protuding fibres from fabric to give a smooth surface. All mostall cotton and spun rayon fabrics are singed. Singeing burns of all fuzz and fibre ends leavingand uneven surface before the fabrics passes through other finishing processes or printing operation.There are 2 methods for singeing. It is done by gas technique (infrared) or by plate technique (the fabric is passed over a heated plate)Fabrics that have been napped (nap is the raised surface on certain kinds of cloth such as velvet) are usually sheared to give an attractive smooth surface. Shearing levels all surface irregularity carvedby the plucking action in the napping process. Shearing is done by a machine with rotating cylinderhaving blades (its action resembles that of a lawn mover). After shearing the fabric is automatically brushed in order to remove the sheared ends of the yarns.It is a cleaning process in which the fabric is treated with hot alkali that removescotton waxes, coloured impurities and other non-cellulosic substance (such as leafand seed coat). Therefore it is a process to make fibre or fabric hydrophilic(water absorbant) to facilitate dyeing and printing process.If a cloth is to be finished while or is to be given surface ornamentation all natural colors must be removed by bleaching. This is also necessary if discoloration or stain have occured during the previous manufacturing process. Bleaching can be donein the yarn stage as well as in the fabric stage.Bleaching agent - Diluted hydrogen peroxide and diluted sodium hypochlorite.Merecrising is an improtant process for cotton fabric. It is also used in the finishinglinen. Merecrising causes the flat twisted ribbon like cotton fibre into a round shape.The fabric becomes much more lustrous than the original fibre and its strength is increasedby 20 percent.Mechanical shrinking is done to minimize shrinking while laundering.Teflon fabric protection provides superior soil and stain resistance for fabrics suitable for apparels for children.Magnisium chloride is used as cross linking agent.Controls the growth of odour causing bacteria.The process of removing the sizing agent.
Natural sizing agents - Starch, Glue, Gelatinete
Synthetic sizing agents - Polyacrylatis, Polyvinyl, alchohols etc) applied to the warp threads to facilitate weaving is desizing.

Different Fabric Dyeing Techniques

Dyeing is a process of colouring fibres, yarns, fabric or garments. Dyeing is of two types

• Chemical
• Natural

Dyeing of textiles is possible at any stage of textile process (fibre to fabric) by different methods.It refers to the dyeing of fibres before it is spun into yarns. It is done by putting loose, unspunfibres into large vats containing dye solutions which are then heated to proper temperature.The term Top refers to fibre of wool from which short fibres have been removed.Dyeing of yarns before they have been woven or knitted into fabrics. The main reason of yarndyeing is for production of multicolored designs such as Plaids, Stripes and Checks. Skein dyeing, package dyeing and beam dyeing are main methods of yarn dyeing.

• Skein Dyeing
  The yarns are loosely arranged in skeins or coils. These are then hung over a rung and immersed in a dyebath in a large container.
• Package Dyeing
  The yarns are wound on spools or cones and are stacked on perforated rods in a rack and then immersed in a tank.
• Beam Dyeing
  It is similar to package dyeing but more economical. Here the yarn is wound on to a perforated warp beam and then immersed in a tank for dyeing.

The dyeing of cloth after it had been woven or knitted is known as piece dyeing. It is mose common method of dyeing used. The various methods used for this type of dyeing includesBeck Dyeing, Jig Dyeing, Pad Dyeing and Jet Dyeing.

• Beck Dyeing
  It is used for dyeing long yards of fabric. The fabric is passed in rope form through the dyebath. This rope of the fabric moves over a rail onto a reel which immerses it into the dye and then draws the fabric up and forward and brings it to the front of the machine. This process is repeated many times until the desired color intensity is obtained.
• Jig Dyeing
  It is similar to the process of beck dyeing with a slight variation. The fabric in Jig dyeing is held on rollers at full width rather than in rope form as it is passed through the dyebath.
• Pad Dyeing
  Padding is also done while holding the fabric at full width. The fabric is passed through a trough having dye in it. Then it is passed between two heavy rollers which force the dye into the cloth and squeeze out the excess dye. Then is is passed through a heat chamber for letting th dye to set. After that it is passed through washer, rinser and dryer for completing the process.
• Jet Dyeing
  Fabric is placed in a heated tube where jets of dye solution are forced through it at high pressures. The fabric too moves along the tube. The solution moves faster than the cloth while coloring it throughly.

Garment dyeing is the dyeing of completed garments. The types of apparel that can be dyed are mostlynontailored such as sweaters, hosiery, denim jackets etc. Tailored items such as suits or dressescannot be dyed as garments because the difference in shrinkage of the various components and linings mishape the art etc.

Different Fabric Printing Techniques

Printing is the process of applying color to the surface of the fabric in definite pattern or design.It is a form of decoration to the fabric.

• Resist Printing
  Some historians consider resist printing to be one of the oldest methods of applying design to the cloth. Early Japanese art of Batik and Stencil printing are examples of resist printing. The basic principles of resist printing is to protect the area of the fabric that are not to be coloured. The basic protection may be paper or metal covering or wax coating.
  Eg: Tie & Dye, Batik
  • Tie & Dye
    The dye is resisted by knots that are tied in cloth before it is immersed in the dyebath. The outside of the knotted portion is dyed but inside is protected. If the knot is firmly tied partial penetration. If the knot is firmly tied partial penetration occurs. When the knot is not tight it causes irregularities of color that produce distinct but attractive designs.
  • Batik Dyeing
    The resist printing method where designs are made with wax or a fabric which is immersed in a dye bath. The main feature of this method is the designed area is resisted by wax and the resisted area does not get colored and printing effect happens.
• Stencil Printing
  In stencil printing the design must first be cut in cardboard, wood or metal. A stencil design is usually limited to the application of only one color and is generally used for narrow width of fabric.
• Screen Printing
  Originally this technique was referred to silk screen printing because the screens were made of fine strong silk threads. Today screen printing is done with the use of either flat or cylindrical screens.
• Block Printing
  The oldest method of printing designs on fabric is block printing by hand. It is not commercially important today because it is too slow. To make block prints the design must first be carved on a wooden or metal block. The dye stuff is in paste form, applied to the design on the face of the block. The block is pressed down firmly by hand on selected portions of the surface of the fabric as many times as desired.