STYLES OR TECHNIQUES OF PRINTING
3 Styles or Techniques of Printing are:
- DIRECT PRINTING
- DISCHARGE PRINTING
- RESIST PRINTING
Block, Stencil, Screen and Digital are methods of direct printing.
Also known as Steam Printing because printed fabric is steamed to fix the colour. Design shapes are made by applying colour paste directly on fabric to form shapes of a design. Colour is directly applied to fabric in the form of a paste containing colouring matter, thickener or binder and other required materials. After printing and drying, the colour is fixed by steaming or curing or thermo fixing or treatment with chemicals.
Most dyestuff classes can be directly printed on fabric. Mordant dyes, Vegetable dyes, Pigments and certain mineral dyes can be applied to fabric through direct printing. Printed effects of Flock, Damask, Foam and Bubble are obtained by direct printing.
Limitations of Direct Printing are:
- Coloured blotches with sharp outlines and free of specks are difficult to produce.
- Difficult to incorporate small or coloured motifs on dark ground.
- Difficult to print fine designs with sharp outlines on knitted fabrics/clothing.
- If not done properly, colours in print may overlap or get displaced.
- If not done properly, print may come-off after a few washes.
Advantages of Direct Printing
- Cost effective
A classical discharge print is obtained when a fully dyed fabric is printed with a chemical agent which removes the dyestuff from the area it is applied on, leaving white in places where the chemical agent was printed. When dyes stable to the discharging agent are added to the chemical discharge agent before printing on fabric, the base colour gets replaced by the additive leaving a coloured/illuminated surface. This technique produces very fine edges in designs. There is no displacement or overlapped colours in the design.
In discharge printing, the whole fabric is dyed fully. A paste containing a chemical discharging agent capable of attacking the dye locally is printed on the fabric as per required design/pattern. The discharge agent printed fabric is then treated (steamed or washed). It shows a white or light pattern on a coloured background. Alternately, a dye resistant to the discharging agents can be incorporated in the discharge paste. The cloth printed with additive+discharge paste yields a 2 colour pattern. The discharging agents may vary from oxidising substances like potassium dichromate to the more usual reducing agents like sodium bisulphite, stannous chloride, sodium hydrosulphite and its stabilised compounds.
- Potassium dichromate is used for discharging Indigo.
- Sodium bisulphite is used in discharging fabric with naphthalated ground.
- Sodium bisulphite+zinc dust is an effective reducing agent for discharge printing of Acid dyed silk fabric.
- Rongalite is used as a discharging agent for Azoic, Direct, Acid and Reactive dyed fabrics.
ADVATAGES OF USING DISCHARGE PRINTING
- White and coloured patterns can be produced on dyed dark coloured grounds.
- Gives the best depth, fullness and richness of colour.
- The pattern thus produced would almost be impossible to produce in the same quality with a double printing of complementary colours.
The resist style relates to the production of white and coloured patterns on variously coloured grounds by the resist applied to the fabric before it undergoes any dyeing or mordanting. Batik and Ajrakh printing are examples of this technique of printing.
In resist printing, the printed portions are so treated that dyes will not be taken in the resist printed areas, leaving behind a white pattern on a darker ground. When a pattern of 2 colours is to be printed, the resist material is first printed in admixture with a dye which withstands its action, which will give a coloured pattern. The whole fabric is then dyed with a dark background such as aniline black. The black will not ‘go’ on the printed pattern owing to the presence of ‘resist’ and after washing, a coloured pattern on a dark background will result. The resist agents may either be mechanical or chemical or both.
In the tie-dye process and Bandhni printing a portion of the hank or fabric is tied by rubber bands or cotton thread before dyeing it, to resist the bound portions(which remain white), the rubber band or the thread acts as a mechanical resist.
In Batik printing, portions of the fabric required to remain undyed are treated with wax and the whole fabric is the dyed with dyestuff which can be dyed at a temperature below the melting point of wax. In this case wax acts as a mechanical resist. Stannous chloride (tin salt) and citric acid may be cited as chemicals which are used a resist. Tin salts = Naphthol dyes, Citric acid = Reactive dyes.