Transfer Printing Process | Advantages/Disadvantages of TransferPrinting

Transfer printing is the term used to describe textile and related printing processes in which the design is first printed on to a flexible nontextile substrate and later transferred by a separate process to a textile. It may be asked why this devious route should be chosen instead of directly printing the fabric. The reasons are largely commercial but, on occasion, technical as well and are based on the following considerations.

1. Designs may be printed and stored on a relatively cheap and nonbulky substrate such as paper, and printed on to the more expensive textile with rapid response to sales demand.

2. The production of short-run repeat orders is much easier by transfer processes than it is by direct printing.

3. The design may be applied to the textile with relatively low skill input and low reject rates.

4. Stock volume and storage costs are lower when designs are held on paper rather than on printed textiles.

5. Certain designs and effects can be produced only by the use of transfers (particularly on garments or garment panels).

6. Many complex designs can be produced more easily and accurately on paper than on textiles.

7. Most transfer-printing processes enable textile printing to be carried out using simple, relatively inexpensive equipment with modest space requirements, without effluent production or any need for washing-off.

Against these advantages may be set the relative lack of flexibility inherent in transfer printing: no single transfer-printing method is universally applicable to a wide range of textile fibres. While a printer with a conventional rotary-screen printing set-up can proceed to print cotton, polyester, blends and so forth without doing a great deal beyond changing the printing ink used, the transfer printer hoping to have the same flexibility would need to have available a range of equipment suited to the variety of systems that have to be used for different dyes and substrates using transfer technology. 

Transfer Printing Process

In addition factors such as stock costs, response time and so on do not always apply and unlike dyers, most printers are able to operate without steaming or washing by using pigment-printing methods. Thus a balance exists which not only permits but even requires the coexistence of direct and transfer printing. The relative importance of the two methods consequently varies with fluctuations of the market, fashion and fibre preference.

A great many methods of producing textile transfer prints have been described in the literature. Many of them exist only in patent specifications but several have been developed to production potential. They may be summarised most conveniently as below.

Sublimation Transfer
This method depends on the use of a volatile dye in the printed design. When the paper is heated the dye is preferentially adsorbed from the vapour phase by the textile material with which the heated paper is held in contact. This is commercially the most important of the transfer-printing methods.

Melt Transfer
This method has been used since the 19th century to transfer embroidery designs to fabric. The design is printed on paper using a waxy ink, and a hot iron applied to its reverse face presses the paper against the fabric. The ink melts on to the fabric in contact with it. This was the basis of the first commercially successful transfer process, known as Star printing, developed in Italy in the late 1940s. It is used in the so-called ‘hot-split’ transfer papers extensively used today in garment decoration.

Film Release
This method is similar to melt transfer with the difference that the design is held in an ink layer which is transferred completely to the textile from a release paper using heat and pressure. Adhesion forces are developed between the film and the textile which are stronger than those between the film and the paper. The method has been developed for the printing of both continuous web and garment panel units, but is used almost exclusively for the latter purpose. In commercial importance it is comparable with sublimation transfer printing.

Wet Transfer
Water-soluble dyes are incorporated into a printing ink which is used to produce a design on paper. The design is transferred to a moistened textile using carefully regulated contact pressure. The dye transfers by diffusion through the aqueous medium. The method is not used to any significant extent at the present time.

These different methods are considered separately in this chapter since they introduce different scientific and technical factors, and their use is best discussed in the context of the rather different commercial environments.

Block Printing Style | Procedure of Block Printing on Fabric | AfterTreatment of Block Printing

Block Printing

The printing of fabric by hand, using carved wooden or linoleum blocks, as distinguished from printing by screens or roller is called block printing. Block printing is a special form of printing first developed in China. The earliest known example with an actual date is a copy of the Diamond Sutra from 868 A.D (currently in the British Museum), though the practice of block printing is probably about two thousand years old.

Procedure of Block Printing 

The fabric to be printed is washed free of starch and soft bleached if the natural gray of the fabric is not desired. If dyeing is required as in the case of saris where borders or the body is tied and dyed it is done before printing. The fabric is again washed to remove excess dye and dried thoroughly. The fabric is stretched over the printing table and fastened with small pins. This is an important stage as there should be a uniform tension in the fabric and no ripples. Color is mixed separately in another room. Usually pigment dyes are used for cotton.

The first step in block printing is the production of the original document. This is laid on a large, smooth wooden block and fixed into place, reversed. Next, craftsmen of various skill levels, ranging from master carvers for the fine work to less talented artisans for cheaper blocks or less important sections, carve the original painted, drawn or written image into the block of wood. The block can now be covered with ink and used in a press to create duplicates of the original. 

Color paste must be applied to the block surface in a controlled manner, and this was achieved by using a ‘sieve’. A small tub was nearly filled with a starch paste and a waterproof fabric, stretched on a frame, rested on the paste. A piece of woolen fabric was stretched on a slightly smaller frame and fastened to make the sieve. The sieve as saturated with color paste and placed on the waterproof fabric. For each impression, the ‘tiered’ (a boy) spread the color paste on the top surface of the woolen sieve with a large brush and the printer charged the block by pressing it on the wool. The block was then carefully positioned on the fabric, using the pitch pins as guides, and struck with a mallet. After printing a table length with the first block, the second was printed and then any others required to complete the design. 

After Treatment of Block Printing
The fabric, after printing is dried out in the sun. This is part of the fixing process or aftertreatment of printing. It is then rolled in wads of newspapers to prevent the dye from adhering to other layers and steamed in boilers constructed for the purpose. Silks are also steamed this way after printing. After steaming, the material is washed thoroughly in large quantities of water and dried in the sun, after which it is finished by ironing out single layers, which fix the color permanently.

Engrave Roller Printing | Working Procdure of Roller Printing |Advantages/Disadvantages of Engrave Roller Printing Machine

Engrave Roller Printing
Roller Printing also called engrave roller printing. It is a modern continuous printing technique. In this method, a heavy copper cylinder (roller) is engraved with the print design by carving the design into the copper. Copper is soft, so once the design is engraved, the roller is electroplated with chrome for durability. This printing technique developed in the late 19th and early 20th centuries. Until the development of rotary screen printing; it was the only continuous technique. Designs with up to 16 colors present no problem in Roller Printing.

Main parts of Roller Printing

1.  Color doctor
2.  Lint doctor
3.  Blankets
4.  Back grey
5.  Furnishers
6. Color box / tray
7.  Color unit

Roller Printing Machine

Working Process of Roller Printing:

This machine has a main cylinder that is fitted with a large gear.In this printing, the print paste is supplied from reservoirs to rotating copper rollers, which are engraved with the desired design. These rollers contact a main cylinder roller that transports the fabric. By contacting the rollers and the fabric the design is transferred to the fabric. As many as 16 rollers can be available per print machine, each roller imprints one repeat of the design. As the roller spins, a doctor blade in continuous mode scrapes the excess of paste back to the colour trough. At the end of each batch the paste reservoirs are manually emptied into appropriate printing paste batch containers and squeezed out. The belt and the printing gear (roller brushes or doctor blades, squeegees and ladles) are cleaned up with water.

The Defects in the Engrave Roller Printing

1.  Scratches
2.  Snappers
3.  Lifts
4.  Streaks
5.  Scumming
6.  Lobbing

Advantages of Engrave Roller Printing Machine

1.  Higher production without rotary screen printing machine.
2.  14 colors can be used for printing.
3.  Medium design can be produced.
4.  Can be used for printing any style.
5.  Any color is used for printing without higher alkali or conc. acid.
6.  Repeats do not exist as printing is continuous.
7.  Higher production by using single color.
8.  Complex design is possible.

Disadvantages of Engrave Roller Printing Machine

1.  Large design is not possible.
2.  Generally, shedding fault is found.
3.  Higher coloring effect is not possible as like block printing.
4.  Lower production by using more than one color.
5.  Changing time is high. 
6.  Engraving the printing roller is expensive Operation

Difference between Rotary screen printing and Copper screen printing