Monday, February 2, 2015

Resist and Carpet Printing

Resist printing

     Resist printing offers a way of producing an effect similar to that of discharge printing. It also uses dyes that can withstand discharge process, so that high fastness standards are possible.
     The principle of resist printing depends on preventing dye from reaching, or becoming fixed on, defined areas of fabric. Both mechanical and chemical techniques are adopted to provide the resist. Inert compounds such as waxes, resins, fats, china clay, zinc and titanium oxides, and salt of lead and barium all act as mechanical resist for dye.
     Chemical resists, on the other hand, act to prevent the fixation mechanism from operating. Consequently their use requires an awareness of the chemical reactions involved in dyeing the ground shade. A nonvolatile acid, for example, will prevent the alkaline fixation of reactive dyes on cellulosic fibres, an oxidizing agent will prevent the reduction of vat dyes, and so on.
     “Burnt-out” printing techniques have also been developed in which part of the fibres themselves is chemically removed to produce a clear-cut, shaped space in the fabric. Effective results are obtained in this way with polyester/cotton blends, with areas in which the cotton fibres have been “burned away” leaving the colored polyester threads behind. The effects produced depend on the original colors of the two types of fibre and they are achieved without undue loss of fabric strength.
     There are many other possible printing styles are available, notably those producing African prints, some of which have evolved from tie dyeing or the mechanical wax-resist ‘batik’ style.

Carpet printing

     The introduction of carpet printing was stimulated by the desire to expand the possibilities for producing patterned tufted carpets. Various machines have been designed, similar in principle to those used for printing fabric.

Carpet printing
     The above figure shows one type of roller, in which a sponge rubber or nylon flock fibre design caps the cut-out pattern in the rubber surface of the roller. The face of the carpet is pressed successively on to the upper surface of each of four rollers arranged one above the other in a line at 450 to the horizontal. The principle has proved popular but its application is restricted by the relatively poor resolution of detail that it can achieve.
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