Textile Printing

The TAK Printing System

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It can still be found in the carpet industry. With this technique irregular patterns can be produced. The carpet, previously dyed with a ground shade, is provided with coloured spots through dripping. The size and the frequency of the coloured spots can be varied by adjusting the overflow groove placed along the carpet width.

Ink-Jet Printing

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This is another digital printing technique with its origins in paper printing technology that is now also increasingly used in the textile industry. In ink-jet printing, color is applied to the surface of the substrate without variation in firing time, pressure or velocity. For this reason it can only be applied for flat light fabrics, especially silk

Jet Printing

2011-05-01T22:57:00.000-07:00

Jet printing is a non-contact application system originally developed for printing carpets, but now increasingly used in the textile sector.

The first commercial jet printing machine for carpets was the Elektrocolor, followed by the first Millitron machine. In the Millitron printing system, the injection of the dye into the substrate is accomplished by switching on and off a dye jet by means of a controlled air stream. As the carpet moves along, no parts of the machine are in contact with the face of the substrate. Air streams are used to keep continuously flowing dye jets, deflected into a catcher or drain tray. This dye is drained back to the surge tank, filtered and re-circulated. When a jet is requested to fire, the air jet is momentarily switched off, allowing the correct amount of dye to be injected into thetextile substrate. The dye is supplied in continuous mode to the main storage tank to compensate for the amount of dye consumed

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.

An early improvement was made by the first digital carpet printers (Chromotronic and Titan by Zimmer and Tybar Engineering, respectively). These machines are based on the so-called «drop on demand principle», namely the use of switchable electromagnetic valves placed in the dye liquor feed tubes to allow the jetting of discrete drops of dye liquor in a predetermined sequence according to the desired pattern.

In these machines, although the amount of dye applied can be digitally controlled at each point of the substrate, further penetration of the dye into the substrate is still dependent on capillary action of the fiber and fiber surface wetting forces. This can lead to problems of reproducibility (e.g. when the substrate is too wet) and means that it is still necessary to use thickeners to control the rheology of the dye liquor.

The latest improvement in jet printing of carpet and bulky fabrics is now represented by machines in which the color is injected with surgical precision deep into the face ofthe fabric without any machine parts touching the substrate. Here, the control of the quantity of liquor applied to the substrate (which may vary for example from lightweight articles to heavy quality fabrics) is achieved by varying not only the firing time but also the
pumping pressure.

This system can be likened to an injection dyeing process. The name «injection dyeing» is used as a commercial name to define the technology applied on the latest Milliken's Millitron machine. Another digital jetprinting machine commercially available is Zimmer's Chromojet. In the Chromojet system, the printing head is equipped with 512 nozzles. These are magnetically controlled and can open and close up to 400 times a second.

The carpet is accumulated into a J-box, and is then steamed and brushed. When it reaches the printing table it is stopped. The jets are mounted on a sliding frame that can itself be moved in the direction of the warp while the carpet remains stationary during the printing process.

Roller Printing

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In roller 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 color 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.

Rotary-Screen Printing

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Rotary-screen printing machines use the same principle described earlier, but instead of flat screens, the color is transferred to the fabric through lightweight metal foil screens, which are made in the form of cylinder rollers. The fabric moves along in continuous mode under a set of cylinder screens while at each position the print paste is automatically fed to the inside of the screen from a tank and is then pressed through ontothe fabric. A separate cylinder roller is required for each color in the design.

A suction pipe leads from the paste vat to a pump, from where a printing hose leads to the squeegee (dye pipe with squeegee). From here the paste is directed inside the cylinder roller. The fill volume of this so-called printing paste input system is quite high and as a consequence the amount of paste residue that has to be removed at each color change is also fairly significant. Various systems have been introduced in order to lower the volume configuration of this equipment, which also reduces the amount of such wastes. Another possibility, which has also already been implemented in some companies, is to recover and re-use these residues for making up new recipes.

Rotary-screen printing machines are equipped with both gluing and washing devices analogous to those described earlier for flat-screen printing. The belt is washed in order to remove the residues of paste and adhesive. Not only the belt, but also the screens and the paste input systems (hoses, pipes, pumps, squeegees, etc.) have to be cleaned up at each color change

Heat Transfer Printing

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Approximately 7% of printed goods are printed using Heat Transfer Printing

Advantages of Transfer Printing

High quality prints

Fewer seconds

Economical for short runs

Practically pollution free

Disadvantages of Transfer Printing

Slow

Primarily only for polyester

Flat-Screen Printing

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Flat-screen and rotary-screen printing are both characterized by the fact that the printing paste is transferred to the fabric through openings in specially designed screens. The openings on each screen correspond to a pattern and when the printing paste is forced through by means of a squeegee, the desired pattern is reproduced onthe fabric. A separate screen is made for each color in the pattern.

Flat-screen printing machines can be manual, semi-automatic or completely automatic. One type of machine, which is still commonly found in printing houses, can be described as follows.The fabric is first glued to a moving endless belt. A stationary screen at the front of the machine, is lowered onto the area that has to be printed and the printing paste is wiped with a squeegee. Afterwards the belt, withthe fabric glued on it, is advanced to the pattern-repeat point and the screen is lowered again. The printed fabric moves forward step by step and passes through a dryer. The machine prints only one color at a time. When the first color is printed on the whole length ofthe fabric, the dried fabric is ready for the second cycle and so on until the pattern is completed.

In other fully mechanized machines all the colors are printed at the same time. A number of stationary screens (from 8 to 12, but some machines are equipped with up to 24 different screens) are placed along the printing machine. The screens are simultaneously lifted, while the textile, which is glued to a moving endless rubber belt, is advanced to the pattern-repeat point. Then the screens are lowered again and the paste is squeezed through the screens ontothe fabric. The printed material moves forward one frame at each application and as it leaves the last frame it is finally dried and it is ready for fixation.

In both machines the continuous rubber belt, after pulling away the fabric, is moved downward in continuous mode over a guide roller and washed with water and rotating brushes to remove the printing paste residues and the glue, if necessary. After this, the belt is sent back to the gluing device. In some cases the glue is applied in liquid form by a squeegee, while in other machines the belts are pre-coated with thermoplastic glues. In this case thetextile is heated and then it is squeezed by a roller or simply pressed against the rubber-coated belt, causing the glue to soften and instantly adhere.

After printing, the screens and the application system are washed out. It is common practice to squeeze the color from the screens back into the printing paste mixing containers before washing them

Tie and Dye

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Patan Patola of Gujarat is the most extraordinary woven sarees anywhere in the world. It is only in Bali, Indonesia that this type of weave is created. The technique involved is that both the warp and the weft threads are tied in areas where the original is to be retained and then dyed. They continue to tie the threads from the lighter color to the darker color until the final patter is dyed on to the un-woven thread. After this both tied and dyed weft and warp threads are woven and the design emerges. This is known as patola. Internationally this technique is known as ikat, an Indonesian word. The finest example of ikat known in the world is the patola of Patan, which is the double ikat, where the warp and weft are tied and dyed before they are woven. The pattern emerges as the warp is laid out and then gets brilliantly delineated when the weft is thrown across.

Tenganan in Bali is the only other centre where double ikat is still practiced. Salvi communities, who weave the patola in Patan, have perfected this technique into a fine art.

The warp for the border and the body are prepared separately. The warp is then stretched in a narrow long street using rods to stretch the threads. The pattern to be created is marked by using powdered charcoal mixed in water. The weft is prepared by wrapping it around two rods, which are inserted in to a beam stretched according to the required width. Inserting thick twisted cotton threads between them separates the groups of weft. The pattern is then tied. First those sections, which are remaining white, are tied, since the design is outline in the base color. The main pattern color emerges during this process. The final dye bath is the main background color, which more often than not, is red. Each color requires that the tied sections are untied and threads to be protected are tied and then dyed. This process is painstaking and great precision is required from the very beginning, when the warp and the weft are prepared, and when the warp threads are laid.

The dyed warp threads are once again stretched to their entire length, which is normally 20 yards, needed for these sarees. The warp for the borders is attached at this stage and the entire warp of the saree is then tied to the rods, rolled and stored ready for weaving. This is then mounted on the simple single harness loom and the weft threads are reeled into the shuttle bobbins. The beam is placed at an angle with one side raised higher. The weft is thrown across and is carefully adjusted often with the use of a long needle so that the patterns synchronize and solid color emerges. So the patterns are based on a square grid, the lines are never distinct, causing a slight haziness, giving the impression of viewing the pattern through flowing water.

Patan used to export patolas from ancient times to the Far East. In Cambodia, Thailand and Indonesia the patola played an important part in rituals and ceremonies and became an integral part of their lives. A large scarf or kerchief with the line motif was a popular item, which was sent out from Multan to Java. Since Cambay, todays Khambhat, was another port from which patolas were exported, the name Cambay became associated with them. Some of the motifs drawn from the repertoire of these countries were absorbed into the designs woven on the sarees for local use.

The sarees have patterns like the pan bhat, leaf pattern, the nari-kunjar-jhar, lady, elephant, enclosed in a border or a jal, trellis work pattern. Chhabadi bhat, basket design, chowkdi bhat, square or lozenges, pattern with flowers in each corner, ratan chowk bhat, the jewelled square, raas bhat, the circular dance design, vohra gaji bhat, the design woven for the Vohra community, and many others.
Today only three families of Salvis continue this tradition in Patan. As a result of a training centre started by the Khadi and Village Industries Board in the late fifties, single ikat sarees are being woven in Rajkot also.

Ikat weaving is done in Andhra Pradesh and Orissa. In Pochampalli, Andhra Pradesh, it is known as pagdu bandha baddabhasi or chilka. The finer tie and dye patterns earlier woven in Chirala were woven in geometric patterns, known as telia-rumal. The origin of this style is not known; some trace it to Gujarat, others to Orissa. Yet another possibility is that it might have been developed in Jalna, since the fishermen of the coast used the rumals. In rural areas people still use the rumal as turban and as an upper cloth called baddabhasi. The telia rumal used to be exported to Aden in large quantities in the early 19th century and were then distributed to the Gulf countries and Africa.

Pochampalli began the production of these rumals as late as the beginning of the last century and began to export them to Iran and the Gulf. The Second World War disrupted the trade causing difficulties to the weavers. In 1955-56, Pochampalli was a poor isolated village with not even a road. Kamaladevi Chattopadhyay, who was the Chairman of the All India Handicrafts Board, went by jeep to Pochampalli. She persuaded the weavers to weave the first cotton saree of 60 counts, which proved to be very popular and the weaver seized the opportunity to begin producing sarees. Later the Board sent two weavers to Varanasi to study silk weaving and this resulted in the production of ikat work silk sarees, for which the demand has been growing steadily. Today Pochampalli is a prosperous village and a few master weavers are also copying the Patan patola.

The weaving of ikat furnishing is now done in the entire Nalgonda district and involves nearly 18,000 looms. Orissa has a distinctive style of ikat known as bandha. In this tradition the single ikat is worked in the warp and the borders are prepared separately. The Sambalpur Vachitraouri sarees has an extra warp pattern on the body and a Hand-Printed, Dyed and Painted Fabrics extra warp pattern on the pallu, while the shkarpara designs of squares of different colors-white, red and black- are in double ikat. The famous silk ikat sarees of Navapatan combine woven patterns on the border and pallu. They also wove calligraphic ikat shawls with verses from Geeta Govinda, which were offered to Lord Jagannath at Puri.

Discharge Printing

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Discharge Printing is also called Extract Printing. This is a method of applying a design to dyed fabric by printing a color-destroying agent, such as chlorine or hydrosulfite, to bleach out a white or light pattern on the darker coloured ground. In color-discharge printing, a dye impervious to the bleaching agent is combined with it, producing a colored design instead of white on the dyed ground.

Discharge printing has been around for decades. But only in the past 7-8 years screen printers in the industry have recognized it seriously. In the early years of discharge printing, the finished discharge print needed to be steamed during the drying process. This discouraged the use of discharge systems in the finished garment arena. The newly developed discharge ink systems are chemically reactive and dont need to be steam-neutralized. This advancement opened the door to discharge printing for the average screen printer.

Discharge printing has the ability to make bright, opaque colors on dark fabrics with a soft hand. Years ago the idea of opaque colors on dark fabrics and soft hand couldnt co-exist.

Successful light-on-dark printing with plastisol relies on increased pigment loads, fillers and other additives to block out the color of the garment. Discharge inks modify the garment color by removing the garment color and replacing it with the new ink color. In simple terms, the discharge ink "bleaches" out the dye in the garment, thus allowing the pigment in the ink to absorb into the shirt fibers.
The real magic of discharge printing can be witnessed when printing four-color process on black 100% cotton shirts. The print before curing appears very transparent. One can barely see the print until the garment exits the oven chamber, where the results can be quite remarkable: bright, vivid colors with a soft hand.

The graphics on the casino gaming tables are printed with discharge inks to avoid the interference of the printed line with the roll of the dice. If the ink on these tables were printed with plastisol, the ink film (because it is a surface print) would change the speed and direction of the dice, thus changing the way the dice land. Discharge ink, on the other hand, provides a dyed-in-the-fabric result, keeping the playing surface smooth. The decrease in the production time is the biggest bonus of all. The fact that you can skip flash curing completely saves hours of production time and eliminates registration problems between the designs colors and the white printer under base used in normal printing on blacks.

However, flash curing can be used in conjunction with discharge printing when printing discharge as an under base.Cleaner and more transparent inks can also be printed onto dark garments with the help of discharge additives. Early discharge additives were designed only for water base inks, but plastisol additives are available.

Characteristics that indicate a Garment will work with Discharge Ink

The garment has to be made of natural fibers (100% cotton)

The dye used in the garment must be dischargeable. The best results are achieved with garments that are 100% cotton and dyed with a reactive dye.

The garment should not have been over dyed (when fabric is re-dyed to another color). This often happens because of a shortage of a certain fabric color or, in many cases, because quality control rejected the fabric color. These rejected colors are then over dyed with a black dye, which will bring nightmares to life when trying to use discharge inks. The discharge ink might discharge the black dye - only to reveal a phantom color underneath

Always test your garment to see if it is suitable for discharge printing. If you are a major printer doing large-volume printing, be aware that the shirts you order from the mill are tracked by lot numbers and it is possible that a completely different dye may be used from one lot to the next. Let your sales representative know that you are doing discharge printing and mention in writing that you need a dischargeable garment

Points to be Noted

Do not to overlap your separations if you want to print clean spot colors. Butt-to-butt separations are ideal for most discharge printing.

Work with a negative background and allow the dark background of the garment to show through. If you choose to overlap the color separations, overlap the primary colors - red, blue and yellow - to achieve secondary and tertiary colors within the design.

To create the screen for under-basing with discharge ink, sandwich all the color separations together (make a contact sheet or a mask) to allow the discharge ink to be printed under all subsequent colors. (Suitable plastisols can be printed over clear discharge bases. Consult your ink manufacturer for compatibility with plastisol.)

Discharge printing is frequently used for all-over prints because of its soft hand.

Batik

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The term "Batik" is an Indonesian-Malay word
Batik has come to be used as a generic term which refers to the process of dyeing fabric by making use of a resist technique; covering areas of cloth with a dye-resistant substance to prevent them absorbing colors. The technique is thought to be over a thousand years old and historical evidence demonstrates that cloth decorated with this resist technique was in use in the early centuries AD in Africa, the Middle East and in several places in Asia. Although there is no sure explanation as to where batik first was "invented", many observers believe that it was brought to Asia by travelers from the Indian subcontinent.

Despite the fact that batik may have originated elsewhere, most observers believe that batik has reached its highest artistic expression in Indonesia, particularly in Java. The art of Batik was later spread to the rest of the Indonesian archipelago and to the Malay Peninsula where the popularity of the cloth led to the establishment of many other production centers. Batik has become a very central means of artistic expression for many of the areas of Asia and a deeply integrated facet of Asian culture.

Much of the popularity of Batik can be tied to the fact that the batik technique offers immense possibilities for artistic freedom as patterns are applied by actual drawing rather than by weaving with thread.

Another factor in its popularity is the fact that it is so durable. The colors in Batik are much more resistant to wear than those of painted or printed fabrics because the cloth is completely immersed in dye and the areas not protected by resist are allowed to absorb hues to the extent that the colors will not easily fade.

Because of the popularity of batik designs, many batik patterns are used in a wide variety of fabrics. Many fabrics are called batik although they were not made in the resist method. Most purists believe that such cloth has a batik like design but is not true batik which is confined to fabrics made through the application of the originally conceived Javanese methods of resist dyeing.

Modern designers in Indonesia, Malaysia and to a lesser extent Thailand, the Philippines and elsewhere often use batik design elements and often the actual batik clothe in their clothing and accessories. Although most batik fabric is now decorated and tailored by machine, there still remains a considerable market for high-quality, hand-made batik.

Kalamkari Printing

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The kalamkari, handpainted cloths of Sri Kalahasti, Andra Pradesh, works of art drawn entirely by hand, were originally created predominantly for the temples as narrative murals.

These murals tell the stories of the great Hindu epics in picture form. Earlier this century, Christian missionaries commissioned artists to create murals telling the story of Christ.In addition to the epic murals, the Tree of Life theme is very popular and comes in many forms. Artists are also branching out and using the medium for their purpose.

Kalamkari is an exquisite ancient craft of painted and printed fabrics. It derives its name from Kalam meaning Pen, and Kari meaning work, literally Pen-work. It includes hand painting as well as block printing with vegetable dyes. Kalamkari art has evolved through trial and error over the last 3000 years. Techniques of craftsmanship in Kalamkari were handed down within the families from generation to generation.The Kalamkari art of painting undergoes a laborious, slow process of resist - dyeing and hand printing. Many stages have to be undergone before the final results are achieved. Unlike other styles of painting, Kalamkari painting demands a lot of treatment before and after the painting is completed on the cotton fabric. Depending on the treatment of cloth, or quality of the mordant, the colors change accordingly. Every step from soaking of the cloth, to sketching the outlines to washing and drying the cloth, is done carefully and correctly. The world over, people are turning away from dangerous chemical dyes. The harmless, naturally dyed fabrics is used for Kalamkari paintings. The artists believe in using natural dyes, extracted from bark, flower and root. One would be stunned to know that the colour red is obtained by using the Indian madder root, yellow from the pomegranate seed or even mango bark, and black from myrobalam fruit. No chemical dyes are used is producing kalamkari colours. The process used for both schools of Kalamkari painting is more or less the same. The only major difference is that Srikalahasti paintings depend entirely on the brush-like pen whereas the Masulipatnam style uses block-printing procedures. The process done in Srikalahasti is more tedious. The cloth is treated and washed twice, and is painted with alum for two to three times.

Stages

Whitening the cloth by immersing in a solution of goat or cow dung and letting it dry in the Sun for a few days.

The cloth is then treated in Myrobalan solution. Ripe fruits are used in Masulipatnam, raw ones in Srikalahasti. Milk is then added to the solution to prevent the colour from spreading in the next step.

Then iron acetate solution is filled in, either for solid spaces or as outlines, with a brush-pen in Srikalahasti, and wooden blocks in Masulipatnam.

All the areas meant to be red are painted or printed over with the alum solution as a mordant. Mordant is a substance that fixes the natural dye on the material.

After applying alum, the cloth is kept for at least 24 hours. Then the excess mordant is removed by washing the cloth under flowing water.

The dyeing is done for the red colour by boiling with the red coloring materials.

All the portions that are not to be blue are covered with wax.

The waxed cloth is immersed in indigo solution. In Srikalahasti, the blue is painted with the kalam. Then the wax is removed by boiling the cloth in water.

The yellow is painted on to produce yellow and green.

The cloth is finally washed again and dried before the final colours emerge

Screen Printing

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Screen-printing is the most flexible printing process. It can be used to print on a wide variety of substrates, including paper, paperboard, plastics, glass, metals, fabrics, and many other materials including paper, plastics, glass, metals, nylon and cotton. Some common products from the screen-printing industry include posters, labels, decals, signage, and all types of textiles and electronic circuit boards. The advantage of screen-printing over other print processes is that the press can print on substrates of any shape, thickness and size.

An important characteristic of screen-printing is that a greater thickness of ink can be applied to the substrate as compared to the other printing techniques. This allows for various interesting effects that cannot be achieved through the other printing methods. Because of the simplicity of the application process, a wider range of inks and dyes are available for use in screen-printing than for use in any other printing process.

Utilization of screen printing presses has begun to increase because production rates have improved. This has been a result of the development of the automated and rotaryscreen printing press, improved dryers, and U.V. curable ink. The major chemicals used in screen-printing include screen emulsions, inks, and solvents, surfactants, caustics and oxidizers used in screen reclamation
Overview of the Screen Printing Process Screen-printing consists of three elements

The screen which is the image carrier

The squeegee

The screen printing process uses a porous mesh stretched tightly over a frame made of wood or metal. Proper tension is essential for accurate color registration. The mesh is made of a porous fabric or stainless steel. A stencil is produced on the screen either manually or photo chemically. The stencil defines the image to be printed. In other printing technologies this is referred to as the image plate. Screen printing ink is applied to the substrate by placing the screen over the material. Ink with a paint-like consistency is placed onto the top of the screen. Ink is then forced through the fine mesh openings using a squeegee that is drawn across the screen, applying pressure thereby forcing the ink through the open areas of the screen. Ink will pass through only in areas where no stencil is applied, thus forming an image on the printing substrate. The diameter of the threads and the thread count of the mesh will determine how much ink is deposited onto the substrates.

Many factors such as composition, size and form, angle, pressure, and speed of the blade (squeegee) determine the quality of the impression made by the squeegee. At one time most blades were made from rubber, which, however, had a tendency to warp and distort. While blades continue to be made from rubber such as neoprene, most of them are now made from polyurethane, which can produce as many as 25,000 impressions without significant degradation of the image.

If the item is to be printed on a manual or automatic screen press the printed product will be placed on a conveyor belt, which carries the item into the drying oven or through the UV curing system. Rotary screen presses feed the material through the drying or curing system automatically. Air-drying of certain inks, though rare in the industry, is still sometimes utilized.

The rate of screen-printing production was once dictated by the drying rate of the screen print inks. As a result of improvements and innovations in the printing technology, the production rate has greatly increased. Some specific innovations, which affected the production rate and have also increased screen press popularity include:

Development of automatic presses versus hand operated presses, which have comparatively slow production time.

Improved drying systems, which significantly improve production rate.

Development and improvement of U.V. curable ink technologies

Development of the rotary screen press, which allows continuous operation of the press. This is one of the recent technology developments.

Screen Preparation

Screen (or image transfer) preparation includes a number of steps. First the customer provides the screen printer with objects, photographs, text, ideas, or concepts of what they wish to have printed. The printer must then transfer a "picture" of the artwork (also called "copy") to be printed into an "image" (a picture on film) which can then be processed and eventually used to prepare the screen stencil.
Once the artwork is transferred to a positive image that will be chemically processed onto the screen fabric (applying the emulsion or stencil) and eventually mounted onto a screen frame that is then attached to the printing press and production begins

Fabric Block Printing

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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.

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.

In some ways block printing is superior to cast type or moveable type -- for a language such as Chinese which has a very broad character set, block prints are much cheaper to produce for the initial run. The process also allows greater artistic freedom, such as the easy inclusion of pictures and diagrams. However, printing blocks are not very durable, and deteriorate very rapidly with use, requiring constant replacement that limits the possibility of large-scale print runs. Printing blocks can, however, be made from a variety of materials such as wood, linoleum, rubber, or even potatoes.

Dhamadka a village in Gujarat has many printers using mostly madder root for printing red color, rusty iron solution for black color and indigo for blue color. These fabrics are known as Ajrakh. The designs made by block printing are geometric. Many states have block-printing workshops using chemical dyes. However there are only small pockets of areas still using natural dyeing with age-old recipes and local plant material.

In Rajasthan, hand-woven cotton is printed with dye and then over printed with a mud compound used as a resist. When the mud dries the entire fabric is dyed in an Indigo bath. The areas covered with mud retain the red design while blue penetrates the remainder. The twodesigns on sale at this stall were called "young womans cloth" and "old womans cloth."

Masuliputnam in Andhra Pradesh is the main centre of block printing where the fabric is known as Kalamkari. The cloth used generally is mill made cotton, which is first bleached with cow dung and placed in the sun. The next step is to soak the cloth in a mixture of Myrobalan and milk. The Myrobalan contains tannic acid and acts as a mordant helping the dyestuffs to bond with the fibre. The buffalo milk, having high fat content, helps prevent the dye from running. Then the black outline is printed using a solution made with rusty iron soaked in sugar water and bran for several weeks. When the solution comes in contact with the myrobalan it turns black. The next step is printing on another mordant, alum.

This bonds the red dye, Madder Root, after boiling, to the areas that receive the alum. These steps continue until all colours have been printed or brushed on. It is crucial to have a good water supply for washing after printing. It takes weeks to complete all these steps.

Origins of Printing

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Woodblock printing is a technique for printing text, images or patterns used widely throughout East Asia and probably originating in China in antiquity as a method of printing on textiles and later paper. As a method of printing on cloth, the earliest surviving examples from China date to before 220, and from Egypt to the 4th century.

Textile printing was known in Europe, via the Islamic world, from about the 12th century, and widely used. However the European dyes tended to run, which restricted the use of printed patterns. Fairly large and ambitious designs were printed for decorative purposes such as wall-hangings and lectern-cloths, where this was less of a problem as they did not need washing. When paper became common, the technology was rapidly used on that for woodcut prints. Superior cloth was also imported from Islamic countries, but this was much more expensive. The Incas of Peru, Chile and Mexico also practiced textile printing previous to the Spanish Invasion in 1519; but, owing to the imperfect character of their records before that date, it is impossible to say whether they discovered the art for themselves, or, in some way, learned its principles from the Asiatics. During the latter half of the 17th century the French brought directly by sea, from their colonies on the east coast of India, samples of Indian blue and white resist prints, and along with them, particulars of the processes by which they had been produced, which produced washable fabrics.

Jet Printing

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Jet printing may be defined as a process by which the desired pattern with its individual colors is built up by projecting tiny drops of 'ink' (special dye liquors) of different colors, in predetermined micro-arrays (pixels), onto the substrate surface. In all true jet printing systems the ink is projected onto the surface as a controlled series of drops. Usually a set of inks is used consisting of at least three or four primary colors, namely cyan (turquoise), magenta, yellow and optionally black, the so-called CMYK inks. As most ink-jet printers were originally designed for paper printing, the terms encountered in, for example, technical specifications are more related to those used in the reprographics industry than to those that atextile printer would normally employ. Thus reference is usually made to inks rather than dye solutions, pigment dispersions or print pastes. Similarly print resolution is usually defined as dots per inch(dpi) or lines per inch(lpi).

In the field of textiles ink-jet printing is fundamentally different from that of all other techniques, not only because of the non-contact mechanics of the print head but also in the means by which the individual colors of a design are produced. A great deal of computation is necessary to produce each of the millions of pixels in a design and this continues for as long as the machine is printing the fabric. In the past printing machines were adjusted entirely by mechanical methods using the operator's experience and judgment, and although modern impact printing machines may be fitted with more refined feedback devices, these are considerably less sophisticated when compared with the electronic control of jet printers.

In printing, wooden blocks, stencils, engraved plates, rollers, or silkscreens are used to place colors on the fabric. Colorants used in printing contain dyes thickened to prevent the color from spreading by capillary attraction beyond the limits of the pattern or design.

Printing Processes

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Printing, like dyeing, is a process for applying color to a substrate. However, instead of coloring the whole substrate (cloth, carpet or yarn) as in dyeing, print color is applied only to defined areas to obtain the desired pattern. This involves different techniques and different machinery with respect to dyeing, but the physical and chemical processes that take place between the dye and the fiber are analogous to dyeing.
A typical printing process involves the following steps:

Color paste preparation

when printing textiles, the dye or pigment is not in an aqueous liquor, instead, it is usually finely dispersed in a printing paste, in high concentration

Printing

The dye or pigment paste is applied to the substrate using different techniques, which are discussed below

Fixation

Immediately after printing, the fabric is dried and then the prints are fixed mainly with steam or hot air (for pigments). Note that intermediate drying is not carried out when printing carpets (too much energy would be needed for removing the highly viscous liquor)

After-Treatment

This final operation consists in washing and drying the fabric (it is not necessary when printing with pigments or with other particular techniques such as transfer printing).

Printing with Pigments

Pigment printing has gained much importance today and for some fibers (e.g. cellulose fibers) is by far the most commonly applied technique. Pigments can be used on almost all types of textile substrates and, thanks to increased performance of modern auxiliaries, it is now possible to obtain high-quality printing using this technique.

Pigment printing pastes contain a thickening agent, a binder and, if necessary, other auxiliaries such as fixing agents, plasticizers, defoamers, etc.
White spirit-based emulsions, used in the past as thickening systems, are used only occasionally today (mainly half-emulsion thickeners).
After applying the printing paste, the fabric is dried and then the pigment is normally fixed with hot air (depending on the type of binder in the formulation, fixation can also be achieved by storage at 20°C for a few days). The advantage of pigmentprinting is that the process can be done without subsequent washing (which, in turn, is needed for most of the other printing techniques).

Printing with Dyes

Printing Paste Preparation

The process traditionally starts with the preparation of the paste. Compared to pigment printing, the composition of the pastes is more complex and variable, being determined not by the dye used, but by the printing technique, the substrate, the application and the fixation methods applied.

Apart from the dye, printing pastes contain a thickening agent and various other auxiliaries, which can be classified according to their function as follows:

Oxidizing agents (e.g. m-nitrobenzenesulphonate, sodium chlorate, hydrogen peroxide)

Reducing agents (e.g. sodium dithionite, formaldehyde sulphoxylates, thiourea dioxide, tin(II) chloride)

Discharging agents for discharge printing (e.g. anthraquinone)

Substances with a hydrotropic effect, like urea

Dye solubilisers, which are polar organic solvents like glycerine, ethylen glycol, butyl glycol, thiodiglycol, etc.

Resists for reactive resist printing (e.g. sulphonated alkanes)

Defoamers, (e.g. silicon compounds, organic and inorganic esters, aliphatic esters, etc.).

All the necessary ingredients are metered (dosed) and mixed together in a mixing station. Since between 5 and 10 different printing pastes are usually necessary to print a single pattern (in some cases up to 20 different pastes are applied), in order to reduce losses, due to incorrect measurement, the preparation of the pastes is done in automatic stations. In modern plants, with the help of special devices, the exact amount ofprinting paste required is determined and prepared in continuous mode for each printing position, thus reducing leftovers at the end of the run. It is common practice in many printing houses to filter the printing pastes before application, using for example a filter cloth. This operation is especially important for thickeners to prevent free particles from blocking the openings of the screens.

Printing (Paste Application)

After preparation, the paste is applied to specific areas of the textile using one of the following techniques:

Direct printing (which also includes digital and transfer printing)

Discharge printing

Resist printing.

In the case of direct printing the dye is applied to specific areas of a pretreated textile substrate, which can be white or pre-dyed (in light colours).

Discharge Printing

It is possible to speak of discharge printing, if in the fixation process that follows the application of the printing paste there is local destruction of a dye applied previously. If the etched (discharge), previously dyed area becomes white, then the process is called white discharge. If, on the contrary, a coloured pattern has to be obtained in the etched area after the destruction of the previously applied dye, then the process is called coloured discharge. In this case the printing paste must contain a reduction-resistant dye along with the chemicals needed to destroy the previous one. As a result the pre-dyed background is destroyed according to a pattern and the dye, which is resistant to reduction, takes its place.

Reset Printing

In the case of resist printing, a special printing paste (called «resist») is printed onto certain areas of the fabric to prevent dye fixation. In the case of physical resist the material is printed with a difficult-to-wet resin that inhibits the penetration of a dye applied in a second stage. On the other hand, with a chemical resist, dye fixation is prevented by a chemical reaction. Depending on the way the process is carried out, one can speak of pre-printing, intermediate or over-printing resists. One common procedure is the wet-on-wet process in which the resist paste is initially printed, then the material is overprinted with full cover screen and finally fixed and washed. Over-printing resists can be applied only if the dye, already present in the previously dyed and dried fabric, is still in its unfixed form, as in the case of developing dyes.

Fixation

After printing, the fabric is dried. Water evaporation leads to an increase in dye concentration and at the same time prevents the colors from smearing when the fabric is transported over the guide rollers. At this stage the dye is not yet fixed. The aim of the subsequent fixation step is to transport as much as possible of the dye, which is retained by the thickener, into the fibers. This is especially important with dyes, such as vat dyes, for example, that are printed in the insoluble form and are converted into the corresponding soluble state only after reaction with the reducing agents during the fixation process. Fixation is usually carried out with steam. Water vapour condenses on the printed material, swells up the thickener, heats the print and provides the necessary transport medium for the diffusion of the dye. The distribution of the dye between fiber and thickener is an important factor in determining the fixation degree of the dye, which is called the "retaining power" of the thickener. The thickener, in fact, is often composed of polysaccharides and therefore competes with cellulose in retaining the dye. This is the main reason why the fixation rate of a given dye is 10% lower in printing than in dyeing.

After-Treatment

The last step of the printing process consists in washing and drying the fabric. When printing with insoluble dyes such as vat dyes this operation also serves as a means to re-convert the dye to the original oxidised state. In this case, after an initial rinsing with cold water, the printed material is treated with hydrogen peroxide. The process is completed with a soap treatment with sodium carbonate at the boiling point. As already explained, washing is not necessary with pigment printing and transfer printing. This holds for any dyeing/ printing system where thickeners are not needed and where the dyestuff is (nearly) completely fixed (e.g. printing carpet tiles with digital jet printing techniques)

Ancillary Operations

At the end of each batch and at each colour change various cleaning operations are carried out

The rubber belt, to which the fabric is glued during printing (see description below), is cleaned in continuous mode with water to remove excess adhesive and printing paste. Some machines are equipped with water re-circulation systems

The printing gears (all systems responsible for feeding and applying the paste to the substrate) are cleaned by first removing as much as possible of the paste residues and then rinsing with water. In some companies the paste residues are directed back to the appropriateprinting paste batch containers for re-use

The remaining paste in the containers, in which the paste is prepared (paste vats), are in general previously cleaned up by means of sucking systems before being washed out with water. The residualprinting paste collected in this manner is then disposed of.

Overview of Printing

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Textile Printing

Introduction to Textile Printing

Textile printing involves the production of a predetermined coloured pattern on a fabric, usually with a definite repeat. It can be described as a localised form of dyeing, applying colorant to selected areas ofthe fabric to build up the design.

The greatest change in fashion and design that has ever occurred in European textiles was the general introduction of printed fabrics. The first printed fabrics were produced in India and China over four thousand years ago. European textile printing dates from about the tenth century. Until relatively cheap printed fabrics became available, patterns on European dress were the result of weaving or embroidery. Such clothes could only be afforded by the wealthy.

Modern procedures for printing textile goods may be traced back to the block printing of silks in ancient China. In this method a wooden block with a raised pattern on the surface was dipped into the printing colorant and then pressed face down on to fabric. The desired pattern was obtained by repeating the process using different colors. Printing by brushing colorant through thin metal stencils and the transfer of illustrations to the printed page from engraved rollers in a printing press were also widespread by the fifteenth century.

Block printing remained a practical proposition until the roller printing machine was invented by James Bell in 1783. This enabled six colors to be printed at a rate equivalent to that of 40 hand-block printers. The success of the machine depended on the hard rollers, each of which bore an engraving (i.e. an intaglio engraving, in which the depth of the recess on the roller determines the intensity of the print produced) corresponding to a particular color component of the design. The machines were capable of continuously printing six different colors in sequence, with the rollers pressed againstthe fabric.
One of the earliest methods of textile printing was the painting of a design on the cloth using a bamboo pen or brush.The technique was widely used in India to produce a range of elaborate and beautiful designs. Indian printed fabrics began to be imported into Europe in the late sixteenth century. The designs were based upon floral motifs and these formed the basis for early European printed designs. Pencilling was used in Europe until the early nineteenth century. The method supplemented hand-block printing.

From about 1752 engraved flat copper plates were used to produce printed fabrics. The design was cut into the surface of the plate and it was these lines which held the color.The fabric and plate were tightly clamped together in a press to transfer the design to the cloth. Plate prints were made in a single color, usually either red, purple or blue. Extremely detailed images could be produced with the process.

Most plate prints were used as furnishing fabrics, although some small patterns were produced as dress material. Handkerchiefs commemorating political or public events were also produced in quantity. By the end of the eighteenth century plate printing had been almost completely replaced by copper roller printing.This type of printing was used industrially from the 1920s to produce high quality prints in small quantities.

Initially the process was a manual one with two printers passing a rubber-edged squeegee across the screen to force the paste onto fabric. The screen then had to be lifted and moved to print the next section of the pattern. In the 1950s semi-automatic and fully automatic flat screen printing methods were developed. These cut production costs significantly.

This technique is the most common form of textile printing and it involves the application of the printing paste through a fine screen placed in contact with the fabric to be printed. A design is created in reverse on the screen by blocking areas of the screen with a material such as an opaque paint. The screen is then placed overthe fabric and the printing paste is forced through the open areas of the screen using a flexible synthetic rubber or steel blade known as a squeegee.

In hand screen printing the squeegee is drawn steadily across the screen by hand at a constant angle and pressure. However, screen printing is now usually automated, with hand screen printing confined to the high fashion industry. Fully automatic screen printing involves the continuous rotation of a cylindrical screen which is kept in constant withthe fabric, ensuring continuous movement of the fabric through the machine. As the screen rotates, printing paste is forced through the design (open) areas of the screen with the aid of stationary squeegee. Printing paste is pumped into the inside of the screen from a container at the side of the machine at an automatically controlled rate.

In the mid 1950s a new type of screen printing method involving a cylindrical screen was developed.Rotary screen printing involves a series of revolving screens, each with revolving screens, each with a stationary squeegee inside which forces the print paste ontothe fabric . Twenty or more colors can be printed at the same time. The process is much quicker and more efficient than flat screen printing. Since the 1970s it has grown to dominate thetextile printing market.

Both dyes and pigments may be used as colorants in the printing process, although the mechanisms by which they are fixed to the textile are quite distinct. The same forces of dye-fiber association apply to both dyeing and printing and, in principle, the dyes used to give a plain-coloured fabric could be used to print that fabric. However, there are three important characteristics a dye must possess in order to be used in the printing process.

The dye must first be able to dissolve in the small amount of water used in the printing paste.

The dye must be able to diffuse at a reasonable rate from the printing paste on to the fiber, leading to preference for dye molecules with a low relative molecular mass.

The unfixed dye must be capable of being washed off satisfactorily without staining the unprinted areas of the fabric.

Pigments are widely used in textile printing, with about 45% of all textile prints produced using pigments. Unlike dyes, they do not directly associate with the textile fibers but are fixed to the textile with a so-called binding agent. The binding agent is usually a copolymer which is incorporated into the printing paste and forms a three-dimensional film when heated.

If a textile print is washed soon after printing and drying, most of the colorant will be washed away. An appropriate fixing technique is therefore necessary. Fixing techniques are seldom completely successful and it is usually necessary to follow fixing with removal of the unfixed dye, thickeners and other auxiliary chemicals by a washing process. The efficacy of the fixing and subsequent washing process is extremely important to the quality of the print, and mistakes made at this stage of the printing process can be very costly.

Printed dyes are usually fixed by a steaming process, the steam providing the heat and the vehicle for transfer of the dye from the printing paste to thetextile fiber.

Pigment prints are fixed to the fabric simply by baking printed fabric. When the fabric has been printed to an adequate temperature the binder forms a continuous film that incorporates the pigment particles and sticks to the fiber surface. At the same time, if the temperature and pH conditions are suitable, cross-linking between the binder molecules is achieved.

During the last 20 years a digital revolution has occurred that has touched everyone's life. We are now surrounded by digital telephones, audio equipment, cameras, camcorders, TV, laser barcode readers, etc., and many homes possess a computer with access to the Internet. Digital technology has greatly affected many industries including the textile printing market, not only by the introduction of full-width jet printing machines but also in every aspect of conventional print production, from the design stage, through coloration and recipe formulation, screen manufacture and print paste preparation to the final control of the printing machine itself.

Traditional textile printing techniques may be broadly categorized into four styles:

Direct printing, in which colorants containing dyes, thickeners, and the mordants or substances necessary for fixing the color on the cloth are printed in the desired pattern.

The printing of a mordant in the desired pattern prior to dyeing cloth; the color adheres only where the mordant was printed.

Resist dyeing, in which a wax or other substance is printed onto fabric which is subsequently dyed. The waxed areas do not accept the dye, leaving uncoloured patterns against a coloured ground.

Discharge printing, in which a bleaching agent is printed onto previously dyed fabrics to remove some or all of the color.

Resist and discharge techniques were particularly fashionable in the 19th century, as were combination techniques in which indigo resist was used to create blue backgrounds prior to block-printing of other colors. Most modern industrialized printing uses direct printing techniques.

Printing Technology

Textile printing was introduced into England in 1676 by a French refugee who opened works, in that year, on the banks of the Thames near Richmond. Curiously enough this is the first print-works on record; but the nationality and political status of its founder are sufficient to prove that printing was previously carried on in France. In Germany, too, textile printing was in all probability well established before it spread to England, for, towards the end of the 17th century, the district of Augsburg was celebrated for its printed linens, a reputation not likely to have been built up had the industry been introduced later than 1676.

On the continent of Europe the commercial importance of calico printing seems to have been almost immediately recognized, and in consequence it spread and developed there much more rapidly than in England, where it was neglected and practically at a standstill for nearly ninety years after its introduction. During the last two decades of the 17th century and the earlier ones of the 18th new works were started in France, Germany, Switzerland and Austria; but it was only in 1738 that calico printing was first, practiced in Scotland, and not until twenty-six years later that Messrs Clayton of Bamber Bridge, near Preston, established in 1764 the first print-works in Lancashire, and thus laid the foundation of what has since become one of the most important industries of the county and indeed of the country. At the present time calico printing is carried on extensively in every quarter of the globe, and it is pretty safe to say that there is scarcely a civilized country in either hemisphere where a print-works does not exist.

From an artistic point of view most of the pioneer work in calico printing was done by the French; and so rapid was their advance in this branch of the business that they soon came to be acknowledged as its leading exponents. Their styles of design and schemes of color were closely followed-even deliberately copied by all other European printers; arid, from the early days of the industry down to the latter half of the 10th century, the productions of the French printers in Jouy, Beauvais, Rouen, Alsace-Lorraine, &c., were looked upon as representing all that was best in artistic calico printing. This reputation was established by the superiority of their earlier work, which, whatever else it may have lacked, possessed in a high degree the two main qualities essential to all good decorative work, viz., appropriateness of pattern and excellency of workmanship.

If, occasionally, the earlier designers permitted themselves to indulge in somewhat bizarre fancies, they at least carefully refrained from any attempt to produce those pseudo-realistic effects the undue straining after which in later times ultimately led to the degradation of not only French calico printing design, but of that of all other European nations who followed their lead. The practice of the older craftsmen, at their best, was to treat their ornament in a way at once broad, simple and direct, thoroughly artistic and perfectly adapted to the means by which it had to be reproduced. The result was that their designs were characterized, on the one hand, by those qualities of breadth, flatness of field, simplicity of treatment arid pureness of tint so rightly prized by the artist; and, on the other, by their entire freedom from those meretricious effects of naturalistic projection and recession so dear to the modern mind and so utterly opposed to the principles of applied art.