1. TEXTILE PRINTING
Textile printing is the process of applying color to fabric in definite patterns or designs. In properly printed fabrics the color is bonded with the fiber, so as to resist washing and friction. Textile printing is related to dyeing but, whereas in dyeing the whole fabric is uniformly covered with one color, in printing one or more colors are applied to it in certain parts only, and in sharply defined patterns. In printing, wooden blocks, stencils, engraved plates, rollers, or silk screens are used to apply colors on the fabric. Colorants used in printing contain dyes or pigments thickened to prevent the color from spreading by capillary attraction beyond the limits of the pattern or design. Traditional textile printing techniques may be broadly categorized into three styles: Direct printing, in which colorants containing dyes, thickeners, and the mordant or substances necessary for fixing the color on the cloth are printed in the desired pattern. Resist dyeing, in which a wax or other substance is printed onto fabric which is subsequently dyed. The waxed areas do not accept the dye, leaving uncolored patterns against a colored ground. Discharge printing, in which a bleaching agent is printed onto previously dyed fabrics to remove some or all of the color. 1.2. COMPARISON BETWEEN DYEING AND PRINTING
Though the dyeing and printing are the coloration processes using the same classes of dyes and other chemicals, they differ in the following aspects.
Differences between Dyeing and Printing
1. Uniform application on both sides of the fabric surface with single color only. 1. Single or multicolor application on one side of the fabric at selected portions only. 2. Dyes are applied in dilute form.
2. Dyes are applied in paste form.
3. In fabric preparation, Half bleaching is enough.
3. full-bleaching with optical whitener is necessary.
4. Color penetrates through the fabric.
4. Color is applied only on the surface.
5. Fabric need not be in dry condition.
5. Fabric should be in dry state.
6. Requires single machine and the process is simple.
6. Requires complex machinery and the process is also complex. 7. Dyeing consumes more water.
7. Printing consumes less water.
1.3. FABRICS FOR PRINTING
A wide variety of base fabrics are available to print: cotton, polyester, nylon, silk, wool, rayon, and acetate. The base fiber content will determine the type of color system and type of processing to be used. Styling, end use, and economics will also be contributing factors in color selection. Pigment colors are extremely versatile in their application across a range of fiber content and fiber structures. Regardless of fiber content and structure, there are four basic forms of fabric presentation to the printer. Bleached white
No finish –may or may not caustic treated
Bleached white –prefinished
Prefinishing can include one or more of the following:
Softeners, permanent press resins, hand builders, calendaring, and sanforizing. Dyed or tinted
In addition to having a dye or tint applied, these fabric styles may have been prefinished as well. Natural
These fabric styles have been desized and/or scoured only.
They have not been bleached white, so they will retain a natural look – dingry, yellow with motes.
Some of the more common printing requirement differences are summarized as follows:
Bleached white finish – no finish
Assuming effective treatment, this is the ideal print fabric. A very basic print formula should be effective. Basic would be thickener, binder, and color. In some cases, the fabric construction or fiber content may require the addition of an auxiliary to achieve a smooth print appearance. Prefinished bleach white, dyed or tinted, and natural grounds Typically, these styles will require the addition of one or more print auxiliaries. The possible auxiliary is an emulsifier which would equalize...
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