Carpet and yarn printing

HISTORICAL DEVELOPMENT OF CARPET PRINTING 

The initial development of the printing of carpet piece goods took place in the UK shortly after the introduction of tufted carpet production, which followed the lead given by the USA from the early 1950s onwards. The manufacture of broadloom tufting machinery expanded rapidly in the period 1956–64, with continuous improvements in sophistication and productivity following the establishment of such firms as British Tufting Machinery, Cobble Bros (subsequently Singer Cobble), Ellison Tufting Machinery and Edgar Pickering of Blackburn. By 1980 tufted carpets constituted 80% by area of all soft floor coverings made in the UK, and half of these were printed. The desire to print tufted carpets arose because of the then very limited patterning potential of tufting machines; even today, despite the advent of the Hydrashift and Graphics machines, with which it is possible to produce patterns comparable with those seen in two- or three-frame woven Wilton carpets, tufters cannot imitate the more complex multicolour designs of printed carpets. Some improvement in design appeal became available with the introduction of space-dyed and differential-dyeing nylon yarns and with variable-pile-height tufting mechanisms using the ‘buried end’ pattern effect. The UK market was, however, accustomed to traditional Axminster designs and it was therefore opportune to look to printing techniques to achieve greater flexibility. Three prototype machines were designed during 1957–60, of which two involved surface roller printing (a principle that had long been used for some types of textiles and for wallpaper printing) and the third a novel dip printing process. The two surface roller printing machines (developed independently by BTM and Stalwart Dyeing Co) incorporated wooden printing rollers carrying raised designs covered with rubber. Each roller rotated in a trough of dye liquor placed below it, and the pile of the carpet was pressed against the patterned surface by a counter-pressure roller. The BTM machine was not developed further but the Stalwart machine went on to prove popular, particularly in the USA. During the same period Deep Dye Industries, USA, patented a novel machine in which each colour area of the design to be printed was defined by flat-bottomed, shallow troughs fed with dye liquor. The carpet was pressed, face downwards, on to this printing ‘plate’. Thus all the colours of the design were printed simultaneously, which obviated the registration problems of all other methods. The process was particularly good for long-pile carpets, but never achieved widespread usage. The initial preparation of patterns for both these early systems was slow and labour-intensive and required considerable craftmanship, being comparable to the making of hand-printing blocks. Early attempts to use conventional flat-screen textile-printing machines for carpets quickly showed that a completely new design would be necessary to obtain satisfactory penetration of the print paste into the carpet pile. This was first achieved by Carpet Printers Ltd (Bradford Dyers’ Association), who produced a machine that utilised a vacuum slot beneath the carpet surface to achieve penetration of the paste into the pile. The machine, which enjoyed modest success in the UK and America, was very ruggedly constructed for, in contrast to a textile printer, extremely heavy engineering is required for the intermittent transport of the carpet (which may weigh as much as 4 kg m–2 when wet) and also to raise and lower the large screens (up to 5 × 1.2 m in size). During these early days printed carpets carried a definite stigma, as did tufted carpets in general, since they sold at the low-quality end of the market and had poor wear performance, viscose rayon being the main fibre used. Indeed, manufacturers tended to hide the fact that the carpets had been printed by using such phrases as ‘design dyed’ and ‘pattern dyed’! The situation improved, however, with the increasing introduction of nylon carpets and a trend towards finer tufting gauges and low-level loop carpet constructions, which were well suited to carpet printing using the newer flat-screen and later rotary-screen printing machines. From the mid-1960s onwards, following the introduction of the Peter Zimmer machine, carpet printing expanded rapidly, especially in the USA, the UK and, to a lesser extent, Germany. Fashion is cyclical, however, and the carpet trade seems to favour a slow swing between plain shades (or very muted patterned effects) and multicolour Axminster-type designs. This trend, together with increasing competition from Europe and in particular from Belgium, has affected the share of printing in the UK, and the present-day industry is much smaller than it was 10–15 years ago (Table 4.1). Printing carpets in piece form is the most logical approach to achieve minimum stockholding and the fastest reaction to customer demand. For a time, however, certain forms of yarn printing were used for the production of tufted carpets. The production of tapestry yarns for patterned woven carpets was practised over 150 years ago, the main process using a large drum round which a warp of yarns was wound and printed in a complex, preset design. After the dye was fixed and excess dye and chemicals washed off, the yarns were beamed and then woven into a fully patterned carpet on a singleframe Wilton loom. With the advent of tufted carpets, similar techniques were examined with the aim of overcoming the lack of patterning potential of the early tufting machines. It soon became clear that differences in tension, shrinkage and so on between individual yarns comprising the warp were too great, and pattern fit was easily lost during printing, steaming, washing and drying. Two warp-printing processes were, however, devised independently in the USA by Westpoint Pepperell and Crawford/ Mohasco (the latter’s product being subsequently commercialised as the Crawford Pickering machine). Of much greater importance was the warp printing of yarns with random bands of colour to yield attractive, random speckled designs on the tufted carpet, an effect which became fashionable from the 1960s onwards and still remains popular, particularly in Europe. A completely different approach, the knit–deknit method, was also devised in America and is usually ascribed to Fred Whitaker, who claimed to have originated the term ‘space dyeing’. This technique involved pad dyeing of the yarn in tubular knit form, followed by overprinting with multicoloured stripes using surface or engraved printing rollers. Many other space-dyeing systems have since been devised, but somewhat similar effects can now be achieved more economically using producerintermingled, differential-dyeing nylon yarns. None of these approaches to the production of patterned carpets represents the end of the road, however. The use of computer-aided design (CAD) systems for the preparation of textile patterns, which can then be stored as digital information on floppy discs, is now commonplace. This information can then be used to produce negatives for colour separations or, more directly, for the laser engraving of lacquer screens. The next logical step is to use the digital data more directly still, i.e. to drive the printing mechanism, and this has been achieved in various ink-jet printing machines. This type of advanced printing system is typified by Milliken’s Millitron and Zimmer’s Chromojet machines. These systems still use conventional dyes which require fixing and washing off, but there is no basic reason why colour application should not be the very last process applied to the carpet