Printing Method | Method of Printing | Printing Processes | Different Types of Printing Method | Block Printing | Roller Printing | Screen Printing | Transfer Printing | Heat Transfer Printing | Ink-Jet Printing | Carpet Printing | Warp Printing | Resist Printing | Photographic Printing | Pigment Printing | Blotch Printing | Burn-Out Printing | Direct Printing | Discharge Printing | Duplex Printing

Printing Processes:There are five main methods of printing a fabric, these being the block, roller, screen, heat transfer and ink-jet methods. The heat transfer method differs from the others in that it involves the transfer of color from the design printed on paper through the vapour phase into the fibres of the fabric. With the other methods the dye or pigment is applied to the fabric surface through a print paste medium. The ink jet printing process however is a comparatively recent innovation and is referred to as a ‘non-impact’ method, because the print paste is fired on to the textile from a jet which is not actually in contact with the fabric.

DIFFERENT TYPES OF PRINTING METHOD

Block Printing :

The blocks are usually made of wood and the design is hand carved, so that it stands out in relief against the background surface. The print paste is applied to the design surface on the block and the block then pressed against the fabric. The process is repeated with different designs and colours until the pattern is complete. 

Block printing is a slow, laborious process and is not suitable for high volume commercial use. It is a method still practised in the oriental countries where markets exist for the types of printed fabrics produced.

Roller Printing:

Roller printing has traditionally been preferred for long production runs because of the very high speeds possible. It is also a versatile technique since up to a dozen different colours can be printed simultaneously. The basic roller printing equipment, shown in Fig. 7.1, consists of a number of copper faced rollers in which the design is etched. There is a separate printing roller for each colour being printed. Each of the rollers rotates over the fabric under pressure against an iron pressure roller. A blanket and backing cloth rotate over the pressure roller under the fabric and provide a flexible support for the fabric being printed. A colour doctor blade removes paste or fibres adhering to the roller after contact with the fabric. After the impression stage the fabric passes to the drying and steaming stages.

Screen Printing :

This type of printing has increased enormously in its use in recent years because of its versatility and the development of rotary screen printing machines which are capable of very high rates of production. An additional significant advantage is that heavy depths of shade can be produced by screen printing, a feature which has always been a limitation of roller printing because of the restriction to the amount of print paste which can be held in the shallow depth of the engraving on the print roller. Worldwide, some 61% of all printed textile fabric is produced by the rotary screen method and 23% by flat screen printing. 

There are two basic types of screen printing process, the flat screen and the rotary screen methods. 

Heat Transfer Printing :

Transfer printing techniques involve the transfer of a design from one medium to another. The most common form used is heat transfer printing in which the design is printed initially on to a special paper, using conventional printing machinery. The paper is then placed in close contact with the fabric and heated, when the dyes sublime and transfer to the fabric through the vapor phase.

Ink-Jet Printing :

There has been considerable interest in the technology surrounding non-impact printing, mainly for the graphic market, but the potential benefits of reductions in the time scale from original design to final production has led to much activity in developing this technology for textile and carpet printing processes. The types of machines developed fall into two classes, drop-on-demand (DOD) and continuous stream (CS).

Carpet Printing :

The printing of carpets only really achieved importance after the introduction of tufted carpets in the late 1950s. Until then the market was dominated by the woven Wilton carpets and Axminster designs were well established, but by the 1980s tufted carpet production accounted for some 80% (by area) of UK production. Much of this carpet production was printed because the range of patterns possible to produce using tufting machines was limited and there was a desire to produce a greater flexibility of design for these types of carpet

Warp Printing: 

The printing of a design on the sheet of warp yarns before weaving. The fillingis either white or a neutral color, and a grayed effect is produced in the areas of the design.

Resist Printing:

A printing method in which the design can be produced: (1) by applying a resistagent in the desired 

design, then dyeing the fabric, in which case, the design remains whitealthough the rest of the fabric is dyed; or (2) by including a resist agent and a dye in the pastewhich is applied for the design, in which case, the color of the design is not affected bysubsequent dyeing of the fabric background.

Photographic Printing:

A method of printing from photoengraved rollers. The resultant designlooks like a photograph. The designs may also be photographed on a silk screen which is used inscreen printing.

Pigment Printing:

Printing by the use of pigments instead of dyes. The pigments do notpenetrate the fiber but are affixed to the surface of the fabric by means of synthetic resins whichare cured after application to make them insoluble. The pigments are insoluble, and application isin the form of water-in-oil or oil-in-water emulsions of pigment pastes and resins. The colorsproduced are bright and generally fat except to crocking.

Blotch Printing: 

A process wherein the background color of a design is printed rather than dyed.

Burn-Out Printing: 

A method of printing to obtain a raised design on a sheer ground. Thedesign is applied with a special chemical onto a fabric woven of pairs of threads of differentfibers. One of the fibers is then destroyed locally by chemical action. Burn-out printing is oftenused on velvet. The product of this operation is known as a burnt-out print.

Direct Printing: 

A process wherein the colors for the desired designs are applied directly to thewhite or dyed cloth, as distinguished from discharge printing and resist printing.

Discharge Printing: 

In “white” discharge printing, the fabric is piece dyed, then printed with apaste containing a chemical that reduces the dye and hence removes the color where the whitedesigns are desired. In “colored” discharge printing, a color is added to the discharge paste inorder to replace the discharged color with another shade.

Duplex Printing: 

A method of printing a pattern on the face and the back of a fabric with equalclarity. 

Printing Style | Style of Printing | Different Types of Printing Style | Direct Printing Style | Discharge Printing Style | Resist Printing Style

A process for producing a pattern on yarns, warp, fabric, or carpet by any of a largenumber of printing methods. The color or other treating material, usually in the form of a paste, is deposited onto the fabric which is then usually treated with steam, heat, or chemicals for fixation. 

There are three different printing 'styles' used to produce patterned effects on textiles, these being termed direct, discharge and resist. Each of these will be described in turn.

Direct Printing Style

This method involves the direct application of the colour design to the fabric and is the most common method of textile printing. The dyes used for direct printing are those which would normally be used for a conventional dyeing of the fabric type concerned.

Discharge Printing Style

In this method the fabric is pre-dyed to a solid shade by a traditional dyeing process and the colour is then destroyed locally, by chemicals incorporated in the print paste especially for that purpose. The result is a white patterned discharge on a coloured ground. In “white” discharge printing, the fabric is piece dyed, then printed with a paste containing a chemical that reduces the dye and hence removes the color where the white designs are desired. In “colored” discharge printing, a color is added to the discharge paste in order to replace the discharged color with another shade.

Resist Printing Style

In this method of printing the fabric is first printed with a substance called a ‘resist’ which will prevent the dye from being taken up in a subsequent dyeing process. The resist functions by either mechanically preventing the

dye from reaching local areas of the fabric or by chemically reacting with the dye or the fibre, to prevent adsorption. 

A printing method in which the design can be produced: (1) by applying a resistagent in the desired design, then dyeing the fabric, in which case, the design remains whitealthough the rest of the fabric is dyed; or (2) by including a resist agent and a dye in the pastewhich is applied for the design, in which case, the color of the design is not affected bysubsequent dyeing of the fabric background

Washing Fastness Test | Wash Fastness | Description of Washing Fastness | Types of Washing Fastness

Color Fastness:

Color fastness is the ability of fabrics to retain the dyes used to color them. Some fabrics hold dye within their fibers extremely well - like denim - while others do not (mostly synthetic or artificial non-natural fabrics) and tend to “bleed” when they are washed. The denim would therefore be more “color fast” than the other fabric.

The resistance of a material to change in any of its color characteristics, when subjected to washing is called color fasntess to washing.

General Principle:
A specimen of the textile to be tested, with the adjacent fabric attached is subjected to washing under specifiend conditions. Te extent of any change in color and that of the staining of the adjacent fabric are assessed and the rating is expressed in fastness numbers.

There are two types of adjacent fabrics; (1) single fibre fabric and multiple fibre fabric. In the case of multifiber fabric only one specimen is required and in the of single fiber fabric two adjacent faabric are required.

There are various colorfastness tests. Details of washing fastness tests are given below.

Fastness to Washing:
In the test, change in color of the textile and also staining of color on the adjacent fabric are assessed. A 10 x 4 cm swatch of the coloured fabric is taken and is sandwitched between two adjacent fabric and stitched, The sample and the adjacent fabric are washed together. FIve different types of washing are specified as different washing mthods.

Fastness to Wash
Sr.No	Method	Washing severity	Soap+Soda in grams/liter	Time in minutes	Temperature	Steel balls
1	IS:687:79	Very mild like hand wash	5	30	40+/- 2	Nil
2	IS:3361:79	5 times severe than method 1	5	45	50+/- 2	Nil
3	IS:764:79	Mild washing	5 + 2	30	60+/-2	Nil
4	IS:765:79	Severe washing	5 + 2	30	95+/-2	10
5	IS:3417:79	Severe washing	5 + 2	4 hrs	95+/-2	10

 

The solution for washing should be prepared to the required temperature of washing. The liquor material ratio is 50:1 . After soaping treatment, remove the speciment, rinse twice in cold water and then in running cold water under a tap. Squeeze it and air dry at a temperture not exceeding 60°C. The change in color and staining is evaluated with the help of grey scales.

Discharge Style Printing Process | Discharging Agents

Discharge Style Printing:

Discharge means removal and discharging system means the process which can produce a white or colored effect on a previously dyed ground.

This discharging of color from previously dyed ground is carried out by a discharging agent which is actually a oxidizing and reducing agent capable of destroying color by oxidation and reduction.

Discharge Style of Printing

Discharge styles have been important since the earliest days of textile printing..With any industrial process there must be sound technical and commercial reasons for its conception and continuation. In the case of discharge printing, the following considerations determine the usefulness of the process compared with other printing techniques.

1. Printed materials with large areas of ground colour can be produced, the depth, levelness and penetration of which would be difficult, if not impossible, to obtain by a direct printing process.

2. Delicate colours and intricate patterns can be reproduced on grounds of any depth, with a clarity and sharpness that have become the hallmarks of this style. Intricate white patterns lose their crispness if left as unprinted areas in a direct, blotch print, because the print paste spreads unequally in different directions. In addition, a coloured motif fitted into a blotch print either leaves unprinted white margins or forms a third colour where fall-on occurs. In some cases such effects are acceptable, but they can be eliminated by using the discharge technique.

3. The extra processes required and the additional costs of discharge pastes mean that production costs are higher, but the aesthetically superior results give the product a higher value and enable profit margins to be maintained or even improved. The higher costs of discharge printing are often offset when applied to long-lasting designs used for scarves, ties, cravats and dressing gowns. As already indicated, in discharge styles the pattern is produced by the chemical destruction of the original dye in the printed areas. The discharging agents used can be oxidising or reducing agents, acids, alkalis and various salts. An early and, one might say, classical example is the discharge printing of cotton dyed with indigo, the characteristic colour of which can be destroyed either by oxidation or reduction.

Sequence of Discharge Printing Process:
Discharge printing is done as the following way.

Fabric preparation

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Table preparation

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Fabric plaited on the table

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Apply printing paste with the help of screen

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Curing at 190ºc (belt speed 3m/min)

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Delivery

Discharging Agents:
Clearly, the most important methods of discharging are based on reduction. This general method can be varied and adapted to give discharges with most classes of dye in use and on most types of fibre. Indeed, to many printers the terms ‘reducing agent’ and ‘discharging agent’ are synonymous. The most widely used reducing agents are the formaldehyde sulphoxylates. The stability of these compounds is such that only limited losses of sulphoxylate occur during printing and prior to steaming. The use of sodium formaldehyde sulphoxylate (CI Reducing Agent 2, sold as Formosul or Rongalite C) was established as long ago as 1905, when it was recognised that methods based on this reducing agent offered many advantages.

Advantages:

• Large areas of ground of ground color are possible.
• Delicate colors and intricate patterns possible on deep ground color, excellent depth and clarity possible.
• Higher production cost but long lasting unique styles.

Disadvantages:

• It is an expensive process.
• Two stage application involved in dyeing or padding and discharge printing.
• Limited choice of ground and motif colours. Requires rigid process care that any default will lead to damages