Methods of Printing in Textile

What is Printing in Textile?
The word ‘printing’ is derived from Latin, meaning ‘pressing’, and implies the process in which pressure is applied during the printing process. Textile printing is one very important operation in textile manufacturing. It is normally carried out at the fabric stage and sometimes at the garment stage. Printing involves the production of multiple copies of images or designs of various complexities and commonly with a range of colors. The printing process differs from the dyeing methods of color application in that it involves the localized dyeing or pigmentation in a way dictated by the image. In dyeing, colorants are applied uniformly on the textile materials, while in printing they are applied in selected portions as per design using printing tools (block, screen, roller or inkjet printer). The exact printing parameters depend on the type of process and equipment used.

Textile printing is labor-intensive and a skillful job. It is mostly a continuous pro­cess. Due to high production, the operation needs very careful attention and prompt action. Unlike other textile production operations, textile printing demands long expe­rience and high skill of the operators.

Methods of Printing in Textile:
There are several methods for producing colored patterns on cloth, each with its own set of advantages and disadvantages. Among the commercially most important printing methods are:

1. Hand block printing
2. Engraved roller printing
3. Hand screen printing
4. Flatbed screen printing
5. Rotary screen printing
6. Transfer printing
7. Stencil printing
8. Digital textile printing
9. Burnout printing
10. Blotch printing
11. Duplex printing
12. Jet spray printing
13. Photo printing
14. Photographic printing
15. Warp printing

Each method has its own set of applications and is chosen based on factors such as production scale, design complexity, fabric type, and budget considerations. Above methods of printing are described below.

1. Hand Block Printing:
Hand block printing is a technique for printing text, images or patterns. It is the most primitive textile printing technique was that using blocks with raised printing surfaces, which were inked and then pressed on to the fabric. Used as a method of printing on textiles and later paper widely throughout East Asia, it prob­ably originated in China in antiquity. In this process, a design is drawn on, or trans­ferred to, a prepared wooden block. A separate block is required for each distinct color in the design.

Hand block printing is a traditional and artistic method of textile printing that involves carving a design onto a wooden block and using it to apply ink or dye onto fabric. This technique has been practiced for centuries in various cultures around the world.

2. Engraved Roller Printing:
Roller printing is a continuous automatic production in which the process is carried out with the aid of engraved copper rollers. Roller printing, also called cylinder printing or machine printing. A separate engraved roller is used for each color. The size of the print repeat is governed by the printing machine and the size of the roller.

The design was originally engraved on the roller by hand but this was found to be unreliable and time-consuming. Nowadays, a photographic engraving method which involves the etching of the copper rollers with chemicals (strong acids) is used to produce the engravings on the rollers.

Engraved screens are heavy copper rollers whereby the required design is etched or engraved into the copper to produce a ‘cell’ for the print paste. During printing the cell is filled with print paste, and as the screen rotates and the cell comes into contact with the textile substrate, the print paste flows out of the cell onto the substrate in the desired area of the design.

Engraved roller printing is performed by three different methods, namely:

1. By hand with a graver, which cuts the metal away;
2. By etching, in which the pattern portion is dissolved out in nitric acid;
3. By machine, in which the pattern is simply indented.

3. Hand Screen Printing:
Hand screen printing is very much useful for small scale production of garments and fabric pieces of limited length such as sari, t-shirt etc. Hand screen printing is carried out on a fat, solid table covered with a layer of resilient felt and a washable blanket (usually coated with neoprene rubber). Before printing begins, the screens must be carefully positioned on the fabric. The area printed by a screen (screen repeat) must fit exactly alongside the adjacent one. After printing, the fabric is dried by hot steam pipe fitted under the printing table or by hanging over table for air (fan) drying. This is followed by a fixation process by steam or hot air and a final wash.

4. Flatbed Screen Printing:
As the name suggests, the screens for this printing method are flat as opposed to circular as in rotary screen printing. The screen is a woven mesh, made from either polyester or polyamide. Flatbed screen printing machines are mechanized screen printing machines. Large sized screens are placed horizontally along a rubber blanket, keeping defined dis­tances between them. Under stationary condition, the screens hang above the blan­ket. During printing, all screens are brought down on the fabric lying above the blanket. In semi-automatic machines, the squeezes are moved width wise manually, while in fully automatic machines the squeezes are moved mechanically.

The quality of flatbed screen printing is normally governed by several variables, such as mesh size of the screen, the fraction of the open area (i.e., the style of the design), the squeegee angle and pressure, and the number and speed of squeegee strokes.

5. Rotary Screen Printing:
Rotary screen printing uses cylindrical screens as opposed to flat screens. Again, a separate screen is required for each color of the design being printed. More complex designs require the application of many different colors, and typical rotary screen printing machines have the capacity for up to 20 screens.

Rotary screen printing is so named because it uses cylindrical screens that rotate in fixed positions while the fat screens are raised and lowered over the same print location. This printing method, which utilizes seamless cylindrical screens made of nickel foil, combines the advantages of the high-production roller printing and flexible flatbed screen printing. It has proved very successful, especially in terms of large production at relatively lower cost than roller printing. The basic operation of rotary-screen printing is very similar to that of the fully automatic flatbed screen machine.

6. Transfer Printing:
In transfer printing, the design is first printed on to a flexible non-textile substrate (such as paper) and later transferred by a separate process to a textile material. Designs may be printed and stored on a relatively cheap and non-bulky substrate such as paper, and printed on the more expensive textile in proper time with rapid response to sales demand. The production of short-run repeat orders is much easier by transfer processes than it is by direct printing. The design may be applied to the textile with relatively low skill input and low reject rates.

Certain designs and effects can be produced only by the use of transfers (particu­larly on garments or garment panels). Many complex designs can be produced more easily and accurately on paper than on textiles.

Most transfer-printing processes enable textile printing to be carried out using simple, relatively inexpensive equipment with modest space requirements, without effluent generation and elimination of washing-off the printed fabric. Transfer printing has long been used on polyester and polyamide.

7. Stencil Printing:
Stencil printing is a technique that involves using a stencil, which is a template with openings or cutouts, to apply ink, paint, or other materials onto a surface. This method is widely used in various applications, including art, crafting, signage, and textile printing. Stencil printing is a less expensive, cleaner, and simpler alternative to screen printing. It is an easy way to print an image, or several images, repeatedly on a surface, like a poster or a t-shirt. Stencil printing was also practiced in India during the Gupta period (6th to 8th century). The stencil was placed on a fabric and the color was then brushed or sprayed in the cut-out portions, giving beautiful designs. Machine roller printing came in the latter part of the 18th century and its development could be traced to the block print­ing process. This eventually transformed the slow and costly block printing process into cheap mass production, which revolutionized the cotton print industry.

The stencil printing process led to the development of screen printing which works on the resist principle described earlier. In the early days, fine silk meshes were used as the screen. Towards the end of the 19th century, this process was well developed in Japan. Flat screen and rotary screen machines had by that time made this process very popular for printing.

8. Digital Printing:
Digital printing or Ink jet printing is a non‐contact printing system because the print head does not touch the substrate surface. This is a process of creating prints generated and designed on a computer and then printing the design on textile substrates using ink-jet technology. The use of digital technology means that a digital file can be communicated worldwide, and fabrics of identical color patterns and quality can be produced anywhere in the world. This technology reduces traditional order-to-delivery lead times. Ink-jet printing also makes it possible for firms to print images which cannot normally be produced by rotary-screen or flatbed screen printing. For instance, very fine lines and photographic imagery can be printed by ink jet, as well as an infinite number of colors and sizes.

9. Burnout printing:
Burnout printing is a method of printing to obtain a raised design on a sheer ground. The design is applied with a special chemical onto a fabric woven of pairs of threads of different fibers. One of the fibers is then destroyed locally by chemical action. Burnout printing is often used on velvet. The product of this operation is known as a burnout print.

10. Blotch printing:
Blotch printing is a process wherein the background color of a design is printed rather than dyed. The result is that the reverse side of the fabric is typically white. This is a direct printing technique where both the background color and the design are printed onto a white fabric, usually in one operation. Any methods such as block, roller or screen may be used. The ground color is transferred from the cylinder and the motif retains the original hue of the cloth.

11. Duplex printing:
Duplex printing is a method of printing a pattern on the face and the back of a fabric with equal clarity. Printing is done on both sides of the fabric either through roller printing machine in two operations or a duplex printing machine in a single operation.

12. Jet spray printing:
Jet printing is a non-contact application system originally developed for printing carpets, but now increasingly used in the textile sector. Designs are imparted to fabrics by spraying colors in a controlled manner through nozzles. Spray printing systems and first-generation jet printing methods cannot be controlled to produce a pre-specified pattern. Thus, the equipment must first be employed to produce a wide range of effects and only then can selections be made from these by the designer or marketing staff.

13. Photo printing:
In the photo printing, the fabric is coated with a chemical that is sensitive to light and then any photograph may be printed on it. The controlled light passes to the fabric through negative or a photo film, which allows the light to fall on the fabric as per the details in the photo.

14. Photographic printing:
Photographic printing is a method of printing from photoengraved rollers. The resultant design looks like a photograph. The designs may also be photographed on a silk screen which is used in screen printing.

15. Warp printing:
The printing of a design is done on the sheet of warp yarns before weaving. The filling is either white or neutral in color, and a greyed effect is produced in the areas of the design.

Conclusion:
Different methods of printing in textile, including screen printing, digital printing, block printing, and more, offer diverse options for creating intricate designs on fabrics. Each printing method has its strengths and limitations, catering to different production scales and design complexities. Traditional and artistic printing techniques like hand block printing showcase artisanal craftsmanship, while digital printing provides flexibility and precision. The choice of printing method depends on factors such as production requirements, fabric characteristics, and the desired aesthetic. The dynamic landscape of textile printing continues to evolve, with a balance between traditional methods and technological innovations shaping the industry’s future.

References:

1. Principles of Textile Printing by Asim Kumar Roy Choudhury
2. A Novel Green Treatment for Textiles: Plasma Treatment as a Sustainable Technology By Chi-wai Kan
3. An Introduction to Textile Coloration: Principles and Practice By Roger H. Wardman
4. Handbook of Value Addition Processes for Fabrics By B. Purushothama
5. Environmental Aspects of Textile Dyeing Edited by R. M. Christie

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