Sunday, January 13, 2013

PRINTING

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Textile Printing
Printing has often been described as dyeing in a localized area to create patterned design. Creating design interest in fabrics can be accomplished in several ways, including yarn variation (novelty yarns). Weave variation (dobby and jacquard), and color effects in weaving. An additional color design can be created through the process of printing design shapes onto previously woven, knitted, or non-woven fabrics. 

Textile printing uses the same dyes or pigments applied to produce dyed fabric. The same principles of specific dye classes having select fiber affinities and the general fastness characteristics apply equally to printing and dyeing. 

The designs for printed fabrics are an important element of the printed fabrics industry. A continuous supply of new designs are required for this highly fashion oriented segment of the textile industry. 

Dyes or pigments used in dyeing are usually in a water bath solution. When the same dyes or pigments are used for printing, they must be thickened with gums or starches to prevent the wicking or flowing of the print design. The thickened solution, about the consistency of heavy buttermilk, is called the print paste. Some dyes cannot be used in printing pastes for reasons such as insufficient solubility and low color yield. 

The application of a pattern to fabric by the use of dyes, pigments, or other colored substances may be effected by a variety of hand or machine processes. Freehand painting of designs on fabrics is probably the oldest technique for applying ornament, but hand painting is a time-consuming procedure. Furthermore, it does not always result in a uniform repeat of a motif that is to be used more than once. If a design is transferred to a Bat surface that can be coated with a dye and then stamped onto the fabric, the same design can be repeated many times over simply by pressing the decorated surface against the fabric. This process is known as printing. Over many centuries a variety of techniques for printing designs have evolved. Printing can be applied to warp yarns, to fabrics, or to apparel pieces-for example, slogans or pictures on T-shirts. 

In general, printing is a cheaper way of creating designs on fabric than weaving or knitting with different colored yarns. Printing can be done with dyes or pigments. For pigments it is necessary to use an adhesive to bind the colored substance to the fabric. Different methods for applying designs can be combined with a number of printing tools or machines to provide the printer with a variety of processes. 

Methods of Printing 
There are three basic approaches to printing a color on a fabric. Direct, Discharge and Resist. 


Direct Printing 

The principle of direct printing is creation of a colored design by applying a dye or pigment directly onto a textile substrate (yarn or fabric). Discharge Printing. Another approach for applying a color pattern is discharge printing. The fabric is dyed in the piece and then printed with a chemical that will destroy the color in designed areas. 


Batik 

Batik cloth is made by a wax-resist process. The name batik originates in the Indonesian Archipelago, where resist printing has become an important art form. Wax is applied to the areas that the printer does not want to dye. 




Methods Of Direct Printing 
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 


Roller Printing 

Roller printing is the machine method of printing designs on cloth by engraved rollers. It turns out color-designed fabrics in vast quantities at the rate of 1000 to 4000 yards (914-3658 m) an hour. This method of producing attractive designs is relatively inexpensive when compared with any hand method. 


Rotary Printing 

A printing machine that utilizes seamless cylindrical screens made of metal foil was originally developed in Holland. This process is called rotary screen-printing. 


Screen Printing

Originally, this technique was referred to as silk-screen printing because the screens were made of fine, strong silk threads. Today, they are also made of nylon, polyester and metal. Screen printing is done with the use of either flat or cylindrical screens. 


Heat Transfer Roller Printing 

Like traditional roller printing, heat transfer printing is done by passing the fabric around a central drum or cylinder where it contacts a roller for transferring the design. The roller is followed by a heating zone to effect the sublimation of the dye. Since all colors are applied to the fabric at the same time, 


Other Printing Techniques 
Photographic Printing 

Photographic printing is done in a manner similar to the photochemical preparation of screens for screen printing. A photosensitive dye is coated on the fabric, a negative is placed over the fabric, light is applied, and a photographic type of printing takes place. 


Electrostatic Printing 

Electrostatic printing is an experimental process in which a plate with an electrostatic charge is placed behind the fabric. A stencil in the form of the pattern is placed over the fabric. Special powdered inks that can be attracted by the electrostatic charge are passed over the surface fabric, and the inks are attracted into and color the fabric in the open areas of the stencil. 


Flock Printing 

By imprinting an adhesive material on the surface of a fabric in the desired pattern, and then sprinkling short fibers over the hesive, a flocked print may be created.
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