STYLES OF PRINTING

TEXTILE PRINTING

• Textile printing is the process of applying colour to fabric in definite patterns or designs.

• In properly printed fabrics the colour is bonded with the fibre, so as to resist washing and friction.

• In printing, wooden blocks, stencils , engraved plates, rollers, or silk screens can be used to place colours on the fabric.

• Colorants used in printing contain dyes thickened to prevent the colour from spreading by capillary attraction beyond the limits of the pattern or design.

• For cotton printing vat and reactive dyes are generally used.

• Silk is usually printed with acid colours.

• Wool is printed with acid or chrome dyes but before printing it is treated with chlorine to make it more receptive to colours.

• Manmade fibres are generally printed with disperse and cationic dyes.

ALL STYLES OF PRINTING

•Direct printing• Resist printing• Heat-transfer printing •Discharge printing •Mordant printing

DIRECT PRINTING

• It is the most common approach to apply a colour pattern on fabric.

• It can be done on white or a coloured fabric.

• If done on coloured fabric, it is known as overprinting.

• The desired pattern is produced by imprinting dye on the fabric in a paste form.

• To prepare the print paste, a thickening agent is added to a limited amount of water and dye is dissolved in it.

• Earlier corn starch was preferred as a thickening agent for cotton printing.

• Nowadays gums or alginates derived from seaweed are preferred because they are easier to wash out, do not themselves absorb any colour and allow better penetration of colour.

• Most pigment printing is done without thickeners as the mixing up of resins, solvents and water itself produces thickening.

RESIST PRINTING

• In this technique, a resist paste is imprinted on the fabric and then it is dyed.

• The dye affects only those parts that are not covered by the resist paste.

• After dyeing, the resist paste is removed leaving a pattern on a dark background.

HEAT -TRANSFER PRINTING

• The design on a paper is transferred to a fabric by vaporization.

• There are two main processes for this- Dry Heat Transfer Printing and Wet Heat Transfer Printing.

• In Conventional Heat Transfer Printing, an electrically heated cylinder is used that presses a fabric against a printed paper placed on a heat resistant blanket.

• In Infrared Heat Vacuum Transfer Printing, the transfer paper and fabric are passed between infrared heaters and a perforated cylinder which are protected from excessive heat by a shield.

• The Wet Heat Transfer Printing uses heat in a wet atmosphere for vaporizing the dye pattern from paper to fabric.

DISCHARGE PRINTING

• In this approach, the fabric is dyed in piece and then it is printed with a chemical that destroys the colour in the designed areas.

• Sometimes, the base colour is removed and another colour is printed in its place.

• The printed fabric is steamed and then thoroughly washed.

• This approach is on decline these days.

MORDANT PRINTING

• A mordant is a substance used to set dyes on fabrics or tissue sections by forming a coordination complex with the dye which then attaches to the fabric or tissue.

• It may be used for dyeing fabrics, or for intensifying stains in cell or tissue preparations.