HISTORY OF SCREEN PRINTING

HISTORICAL DEVELOPMENT OF SCREEN PRINTING

Screen printing is very familiar terms in textile printing sector. Innumerable kids developed with simple stencils by cutting out shapes from card, and brushing or spraying paint or ink through the holes on to cloth beneath. Industrial stencil sets for lettering are made of waxed card or metal, and incorporate ties to hold the solid areas together and to prevent the centers of letters such as O or P from falling out. The ties produce unsightly lines across the stenciled letters.

History of screen printing in centuries ago, when the Japanese developed the stenciling technique for textile screen printing and brought it to a fine art, they overcame this problem by using human hair or silk threads as ties. These were so fine that the colour spread underneath them, disguising their presence. By the 19th century, the use of this method for printing fabric had spread far beyond history of Japans screen printing and was used worldwide.

History of screen printing in the mid-19th century, French printers introduced the use of a woven silk fabric to provide a continuous support for the paper stencil. For the absolute results the support cloth was stretched across a frame, and the combination became known as a screen. The development was important because in this way not only were ties automatically provided, but the amount of colour paste applied could also be controlled. Soon after, the paper stencil was replaced by a durable paint on the screen fabric.

From this time onwards the advantages of screen printing became increasingly appreciated, especially in fashion houses. Designs are relatively easy to transfer to screens and the frame size can be readily varied. The designer, freed from the restrictions of copper rollers, thus had far greater freedom to choose repeat sizes. In addition, the pressure applied in screen printing is much lower than in roller printing with the result that surface prints with an improved ‘bloom’ or colour strength are obtained, and textured surfaces are not crushed.

The development of screen printing to its modern, highly productive form ran parallel with improvements in the printing screens themselves. Accurate printing of multicolored designs requires stable screens. Screen fabrics made from hydrophilic yarns, such as silk, cotton, viscose rayon or cellulose diacetate, are apt to sag when in contact with water-based print pastes. The introduction of hydrophobic synthetic fibres such as nylon and polyester, especially the latter, made it possible to manufacture stable screens that maintained tension when wet. Their high tensile strength also allowed the fabric to be stretched more tightly over the screen frame, thus improving the accuracy that could be attained. Further improvement came with the introduction of metal screen frames to replace the wooden ones used hitherto, which tended to warp when subjected to a regime of continually alternating wetting and drying.

Strong, stable screens enabled the hand screen-printing process to be mechanised. The first development was the introduction of a movable carriage, in which the screens are mounted one at a time. The squeegee (a flexible rubber blade used to spread the printing paste across the screen and force it through the open areas) was driven across the screen by a motor attached to the carriage. In this method, which is still in use, the fabric being printed is stuck down on long tables and one colour is printed at a time, just as in hand-screen printing.

The 1950s saw the advent of fully automatic, flat-screen printing, the Buser, Stork and Johannes Zimmer machines being prominent. These machines print all the colours in a design simultaneously along the top of an endless conveyor belt (blanket). The blanket and fabric are stationary while the printing operation takes place and then move on when the screens are raised; hence the fabric movement is intermittent.

Fully continuous printing is best achieved using cylindrical (rotary) screens and many attempts were made to form flat wire mesh screens into cylinders, despite the necessity of a soldered seam. When printing through a cylindrical screen with a seam, a line will show across the fabric once every cylinder circumference, unless the seam can be hidden within the design. This was the approach used in the screens manufactured by A J C de O Barros for the Aljaba machine, first introduced in 1954. Barros has written an interesting description of the Aljaba screens and machines.

Wire-mesh screens are too open for printing purposes, and on the early Aljaba screens electrodeposited copper partially filled the holes. This process was later discarded, to be replaced by the use of an outer seamless woven nylon sleeve. Later still, in fact after the closure of the Aljaba company, W Sword introduced a new version of the wire-mesh screen, the Durascreen, in which the holes in the mesh were partially filled with a flexible polymer by electrophoretic coating. The same process can also be used on electroformed nickel screens, extending their life considerably, since the flexible polymer coating reduces the risk of creasing.

An important innovation of the Aljaba company was the duplex machine used by some printers to print both faces of curtain fabrics. The fabric ran vertically upwards between pairs of screens, print paste being forced through the screens by metal roller squeegees.

The invention of seamless screens of electrodeposited nickel was the really significant step which heralded the rapid expansion of rotary-screen printing. Peter Zimmer (Austria) introduced the galvano screen in 1961, and Stork (Holland) the lacquer screen in 1963. These screens soon proved to be superior, in many respects, to Aljaba screens. When Stork introduced their machine, based on the lacquer screen, at the 1963 ITMA Textile Machinery Show at Hannover it was an immediate success, so much so that Stork decided to stop manufacturing fully automatic flat-screen machines. Between 1964 and the end of 1972 Stork sold 600 rotary machines throughout the world.

Machines using rod or roller squeegees, such as those manufactured by Peter Zimmer and Mitter, have been very successful in printing wider substrates, such as carpets. Rotary-screen machines have also been used to print paper for the transfer printing process. Currently rotary-screen printing is the predominant printing method worldwide, having substantially replaced copper-roller (intaglio) printing.

ENGRAVED-ROLLER PRINTING; COLOUR VARIABLE PRINTING

Two-colour engraved roller printing machine

Principles of operation of engraved roller printing:
A traditional two-dye engraved roller printing machine is shown diagrammatically in Figure. Each engraved cylinder (F) of roller printing machine, mounted on a steel mandrel (L), is forced during printing fabric as it travels around a pressure bowl (A) of printing machine with resilient covering (B). The engraved roller printing machine must be of robust construction because pressures of several tonnes are applied and each mandrel is driven by a single large crown wheel. As the rollers rotate, a furnishing roller (G) transfers print paste (colour) from a colour box (H) to the engraved cylinder, filling the engraving and smearing the whole surface. This surface colour is almost immediately removed by the steel blade known as the colour doctor (J). This doctor must be precisely ground, sharpened and set, at the optimum angle and tension, to leave the surface perfectly clean. Engraved areas retain the colour in parallel grooves and the doctor blade is ‘carried’ on the crests between the grooves.

The fabric is then forced into the engraving and most of the printing paste is transferred. The cushion between the pressure bowl and the engraved roller clearly plays a critical role in the uniform transfer of colour across the fabric width and along its length. The cushion is obtained by rolling about ten layers of a lapping fabric with linen warp and woollen weft around the pressure bowl. Any irregularity, including any ridge at the end of the lapping that may develop if it is not perfectly matched with the first end, can cause a visible fault in a critical print. The cushion progressively hardens with use and requires changing from time to time. Because the lapping must be protected from colour printed beyond the fabric edges or forced through the fabric, an endless printing blanket (C) must be used and washed and dried continuously before returning to the point of printing. In addition, a back-grey (D) is used to absorb colour and give greater resilience, unless the blanket provides enough resilience and is able to hold the excess colour satisfactorily. In the printing of lightweight or knitted fabrics the woven back-grey is often ‘combined’ with the fabric to be printed, using small amounts of a suitable adhesive. This helps to maintain dimensional stability under the tension applied during printing.

After transferring its colour, the engraved roller is cleaned by a brass blade known as the lint doctor (K). This removes any loose fibres that may have stuck to the surface of the roller and could become trapped under the colour doctor, where they could cause a colour streak to be printed. The lint doctor on the second (and any subsequent) roller may be seen to remove a significant amount of the previously printed colour that the roller takes up from the fabric. Without the lint doctor, this colour would be carried into colour number two and cause rapid contamination, although some contamination is unavoidable because the lint doctor will push a little colour into the empty engraving.

The printed fabric is now separated from the back-grey and blanket and carried on to the drying section of the engraved roller printing machine, avoiding any contact of the print face until some drying has been achieved. In the UK drying cylinders were often used in the past, but hot-air dryers are more universally appropriate.

On a multi colour machine the printing rollers, with colour boxes and other auxiliary equipment, are arranged around a larger pressure bowl with minimum separation of the rollers. Setting and maintaining the correct registration (that is, fitting each colour of the design relative to the others) requires an arrangement for separately rotating each roller a small distance while the drive to all the rollers is engaged. The original box-wheel device was elegantly simple but introduced a serious hazard to the printer’s hands as it required the insertion of a rod, or tommy key, into a hole in a wheel rotating near the meshing drive gears. A safer device has been described by Gleadow, who has also given a more detailed account of engraved roller printing.

It is necessary to correct the pattern fit from time to time during printing, because each roller will have a different effective circumference if there are significant differences in the area engraved or the pressure applied. Thus the fabric will be stretched or allowed to relax to a minute degree between rollers and the fit of the design will gradually be lost. As already noted, combining with a back-grey can improve stability.

Good pattern fitting also requires a perfectly rigid fit of the engraved cylinder on its mandrel. To this end, the cylinders and mandrels are tapered and a forcing jack is required to mount and to remove the mandrel. In addition a key, or ‘tab’, on the inside of the cylinder engages in a slot along the mandrel.

MACHINE USED FOR BLOCK PRINTING

Mechanization of block printing:
In 1834 a machine that automatically performed all the actions of block printing was invented by Perrot (it became known as the Perrotine), and achieved some success in block printing process. Mechanization block printing was limited to three dyes and a maximum repeat of only 15 cm and operation of the printing could not be truly continuous, but the three colours were printed simultaneously in that printer. Storey gives an illustrated account of this printing machine, and of hand block printing.

Much earlier, attempts had been made to obtain continuous surface printing using wooden rollers, but the difficulty of uniform application of the printing paste to the roller was the common problem. In about 1805, however, a rotating woollen fabric ‘sieve’ was introduced in Accrington, and used successfully thereafter. The other essential step of block printing was the preparation of a raised pattern on the roller by inserting copper outline strips and felt, just as in hand block printing. This technique of surface block printing was used until recently for printing furnishing fabrics and for wallpaper, but was never as important as the copper roller method. It had the advantages of requiring low pressure and avoiding the dyes contamination that occurs on engraved roller printing machines, because no contact was made with previously printed colour, but the cost of roller making of roller printing was high. Wallpaper printers found that inexpensive rollers could be cast from epoxy polymers and the nonprinting areas were easily cut away, but they did not carry enough colour to print most fabrics.

Essentially the same method of block printing has been used for printing polymer film, other packaging materials and transfer paper, but is then usually known as flexographic printing. The design is built up on wooden rollers by the application of rubber mouldings and the colour is applied by uniformly engraved metering rollers.

Surface printing machines with woolen fabric sieve

A Pressure bowl
B Surface roller
C Furnishing blanket moving over rollers 1, 2 and 3
D Colorant trough
E Plain furnishing roller rotating in colorant
F Second furnishing roller spreading colorant evenly on the blanket
G Blanket for extra resilience round the pressure bowl
H Back-grey
I Fabric to be printed
J Printed fabric

BLOCK PRINTING; SURFACE PRINTING METHODS

Block making for surface printing:
The typical hand block printing had no large, uniform areas of colour but was skillfully built up from many small coloured areas, because wooden surfaces larger than about 10 mm in width would not give an even print. Block printing had the advantage that a motif such as a flower would have an effect of light and shade obtained from three or four blocks, each block printing contains different depth of the same colour, or a different hue. This obviously meant that a lot of blocks were required. Special care was needed in setting the adjacent parts of the design during block printing. If the block printing design had a large repeat there would be a multiplication of the number of blocks because the size of a single block for block printing was limited to about 45 cm square and its weight to about 5 kg. Most blocks for block printing were much smaller than this, perhaps because many printers were women.

Wood blocks surface printing with brass strip and pin inserts

Block making for surface printing required patience and skill. A fairly hard wood was required, such as pearwood, and four or five layers were usually glued together with the grain running in different directions. The printing design was traced on to the surface and a fine chisel used to cut away the non printing areas to a depth of perhaps 1 cm. To obtain more detail from some blocks, strips and pins of copper or (more usually) brass were hammered into the wood. In the 19th century some blocks were made with the printing surface entirely in brass, which gave very delicate prints.
 

Wood blocks of surface printing with cast type-metal printing surface without pitch pins

 Another technique for surface printing used for complex printing designs was to prepare a mould, use this to cast the image from molten type metal, fasten the casting to the block, and then grind the surface perfectly flat. When large areas of solid colour were required, the areas within metal or wooden outlines were filled with felt, which would absorb and print the paste uniformly. Finally, each block required corner ‘pitch pins’ which printed small dots; these allowed the succeeding blocks to be correctly positioned by accurately locating the pitch pins above the already printed dots. A less precise form of block printing is practised in the production of, for example, Africa prints using large plywood blocks with polyurethane foam printing surfaces.
 

The printing table for surface printing:
A very solid table was needed; it was topped with flat surface slabs of stone or iron covered with a resilient blanket and a sheet of waterproof material for block printing. A back-grey of plain cotton was usually stretched over the table, to absorb any surplus colour for surface printing. Ideally the back-grey would be gummed to the table and the fabric to be printed could be pinned to it, for tight-fitting patterns.

The printing process of block printing:
Printing 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 water proof fabric, stretched on a frame, rested on the block printing paste. A piece of woollen fabric was stretched on a slightly smaller frame and fastened to make the printing sieve. The sieve was saturated with printing paste and placed on the waterproof fabric. For each impression of block printing, the ‘tierer’ (a boy) spread the printing paste on the top surface of the woollen 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 completing the design. The fabric was then transferred to a few elevated surface printing rollers or rods and allowed to dry, while the next table length was printed.

COLORANTS OF PRINTING, DYES OR PIGMENTS USED IN PRINTING

DYES OR PIGMENTS USED IN PRINTING
The selection of colorants of printing is very important terms for printing history. The earliest colorants used in printing were undoubtedly mineral pigments, but the style dyeing was also in early use in printing. Today the availability of a wide range of excellent organic pigments and of reliable pigment binders gets in printing market and has led to the increased importance of pigment printing. More than 50% of the world’s textile prints were pigment-printed in 1990 of printing history. The substantial importance of polyester/cellulosic (cotton, jute, flex, hemp) blends has increased their use, because of the complexity of printing these substrates with dyes.

It has proved possible to reduce, though not to eliminate, the extra costs of printing attached to the general use of dyes, due to their requirement of steam fixation and after-washing. In 1984, Schofield recorded the impact of changes in dyes over a 50 year period. Reactive dyes now account for 25% of print colorants, disperse dyes 10%, vat dyes 9% and azoics 3%. In all dye ranges a high priority has been given to selection for ‘robustness’, or the ability of a dye to give reproducible results due to low sensitivity to likely variations in conditions. The tasks facing colorists in the early years of the century were far harder than those of their successors today but their achievements, as judged by prints to be seen in the museums, were highly creditable.

The development of printing techniques from the earliest days has been reviewed. In the further articles those techniques now will substantial use is considered in detail. Here we must examine the surface and intaglio techniques in sufficient detail for an appreciation of their past and present value.

HISTORY OF FROM STENCILS TO ROTARY SCREENS PRINTING

HISTORICAL DEVELOPMENT OF FROM STENCILS TO ROTARY SCREENS PRINTING
The technique of stencil printing, initially used for simple patterns on walls and for lettering, was developed into an intricate craft for fabric printing in Japan [8]. In the 17th century the idea of tying together parts of the stencil with human hair initiated the development. Then in 1850 in Lyons the first use of silk gauze as a supporting stencil base was employed, and the technique soon became known as screen printing. This proved to be the answer to the requirements of the couture business, partly because the designers found it well suited to their needs, but also because strong, bright colours could be obtained with minimal restriction on repeat dimensions. The use of hand screen printing grew in the period 1930 to 1954 and was ideal for the growing quantities of man-made fibre fabrics, especially the knitted fabrics. With the successful mechanisation of flat-screen printing and ultimately the use of rotary screen machines, the days of the copper roller machine were numbered. In 1990 the worldwide production from the latter was estimated to be only 16% of the total, while 59% was from rotary screens. In the UK the switch from copper roller printing was initially slow but then accelerated, the technique’s share falling from 90% in 1960 to only 6.6% in 1992. In the same period the output from rotary-screen printing grew from perhaps 1% of the total to 82.8%. Thus the machine introduced in 1785 dominated the industry for some 160 years, but is now fast disappearing. The use of copper rollers is still important in the gravure method of printing in colour on paper. The dimensional stability, uniform thickness and surface smoothness of paper make it possible to achieve a much greater precision than is possible on textile fabrics. Even in the paper printing sector, however, cheaper methods have captured a significant fraction of what was the market for gravure machines. This is relevant to our consideration of textile printing in relation to transfer printing, which provides a valuable approach to garment printing and for the printing of polyester fibre fabrics, and which currently holds about 6% of the total market.

HISTORY OF ENGRAVED COPPER PRINTING

HISTORICAL DEVELOPMENT OF ENGRAVED COPPER PRINTING
The most significant innovation of the century, however, was the adoption of the intaglio technique, first in Dublin by Francis Nixon in 1752, then in London. European artists had discovered the possibilities of reproducing pictures from an engraved metal plate in the 15th century. Copper could be incised by hand with a sharp steel tool, and was the preferred metal. Application of ink to the plate and cleaning the unengraved surface with a cloth preceded the careful laying on to the plate of a sheet of moistened paper which was then passed, on a board, through a press. This consisted of two rollers, with blankets providing some resilience and ensuring good contact with the ink. Nixon realised that this technique could be used in modified form for printing textile fabrics, thus providing a vital step in the movement towards a machine-based industry.

The Italian word intaglio had been applied to engraving of gemstones and metal.
Wood engravings were obtained by printing from a surface left raised after cutting away negative areas, as for block printing on fabric. Intaglio prints produce much finer line and stipple effects. The effort required for hand engraving was soon reduced by application to the plate of a thin coating of blackened wax, which is easily scratched through to allow a controlled etching of the copper in an acid bath. Tonal effects are obtained by recoating with wax, except for the areas for dark tones, which are then etched to a greater depth. Artists who excelled in the use of this technique included Dürer, early in the 16th century, and later Rembrandt, Turner and Picasso.

The ‘obvious’ extension to prints on fabric had only occurred, before Nixon’s time, in the production of maps on silk and similar applications where fast dyes were not required. Nixon took his technique to London in 1755, where there was already an established group of printers using block and wax-resist techniques, and by 1761 ‘an entirely new type of printed fabric decorated with figures, landscapes and architecture’ confirmed the English pre-eminence in the field [5]. It was the delicacy of these prints, together with the boldness of large repeats that made London the world fashion centre for a while. It was also a recovery of the fine but bold style of the best Indian prints but with a European signature. Schuele took the technique to Augsburg in 1766 and Oberkampf started using it in Jouy in 1770.

Copper plate printing did not displace block printing, because the skills required were greater and it was difficult to ensure that the design repeats fitted satisfactorily. The fabric was moved with the plate for each impression and the plate had then to be returned. The fabric tended to move out of line and its position and squareness had to be corrected by hand. The perfect answer to the fitting problem was to turn the copper plate into a cylinder, and this would allow truly continuous production at high speed. Even as early as 1699 it was claimed that an engraved (presumably wooden) cylinder had been used successfully [1], and patents were taken out in England in 1743 and 1764 for cylinder machines. It was 1783, however, before all the requirements for successful engraved copper roller printing were actually worked out and patented by Thomas Bell, a Scotsman. The first machine was in use in 1785 in Lancashire, and by 1840 there were 435 machines in England alone. The vital feature of Bell’s machine was the use of a sharp steel ‘doctor’ blade to remove all the colour paste from the unengraved surface of the roller. The name given to the blade was derived from the word abductor, because it took away the unwanted ink.

Although considerable skill was required to engrave and use copper rollers, the increase in productivity resulting from their use was so great that block printing inevitably declined. Turnbull says that ‘where by block it was only possible to print of the simplest pattern about six pieces per day, it was now possible to print by machine up to 500 pieces per day of a similar pattern’ [6]. This was a revolution even more significant than those occurring in the spinning and weaving sectors, and there were inevitable disputes and strikes. But there could be no putting the clock back. Edmund Potter said in a lecture to the Society of Arts in 1852 that the output of printed calico in England increased from 1 million pieces (of 30 yards) in 1796 to 7 million in 1821, and to 20 million in 1851. By 1851 the number of machines had reached 604, while the number of blocking tables declined from 8234 in 1840 to 3939. By 1880 very few tables were still in use, except for the printing of silk and specialist styles. The rise of the roller machine reached a peak in 1911, when production from British printworks amounted to 1400 million yards, of which 90% was exported [7]. Worldwide, roller machine production accounted for more than half of the total yardage printed until 1976, almost 200 years after Bell’s 1783 patent.

While copper roller machines proved ideal for high-volume, low-cost printing of woven cotton fabrics, there was always a market for small-scale production of individual designs, especially on silk, wool and, later, on man-made fabrics. For these, roller printing was not suitable at all. The costs of engraving and setting up the machine for each run were high, and long runs were therefore essential. Block printing satisfied the demand for some time, but an alternative, fundamentally different approach emerged.