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pigment printing process does not need the complex The first purpose of colour management in the digital
steaming and washing steps. Since the pigment dye workflow is to render the ambiguous RGB values
is printed only on the top layer of the fabric without unambiguous by associating them with a specific
any chemical bonding, the textile fabric needs to be colour as perceived by humans, that is, colour
condensed for a few minutes to fix the pigments. appearance. Colour management accomplishes this
Consequently, the pigment printing process requires goal by associating a profile with each image.
significantly less water due to the omitted washing Profiles can be quite complex and are used to
step. Due to the insolubility of the pigment particles, correlate ambiguous RGB, CMYK, and grey device
the sedimentation of the particles could result in values with numbers in a system directly based on
problems of nozzle clogging in the fine nozzles of human perception. The second purpose of colour
inkjet printing machines. Firstly, all the inks need to management is to match that specific colour
be well stirred before using; and secondly, the appearance as the image travels through the
necessity of a print head with a circulating system reproduction chain from camera or scanner, to the
becomes more and more important. The circulation display, and then into print.
provides a continuous flow that avoids sedimentation
and thus clogging the nozzles. In particular, the white Colour management for textiles is complex. Firstly,
pigment inks mostly based on the inorganic compound extended ink colour sets are typically used, with six
titanium dioxide need those circulating systems. or more ink colours. This means a much larger set of
colour patches needs to be printed to give an
Pigment inks have the potential to have a big future in accurate profile, because of the larger number of ink
digital textile printing, especially when it comes to combinations that can be created. Secondly, there is
A great advantage of the digital printing, especially printing on polyester. An ideal solution would be to environmental aspects and process simplification. As likely to be a larger portfolio of textile substrates
for the fashion industry, is the ability to print have an ink suitable for all kinds of textile substrates. well as used on commonly used textile materials used, all of which require profiling. Thirdly, the printed
on-demand in small quantities down to a lot size of This request is to be fulfilled by the use of pigment such as cotton, polyester and polyamide, pigmented image needs to be processed through all of the
one. The worldwide output of digitally printed textiles inks. inks can also be used to easily print on mixed fabrics stages to a finished textile before profiling, otherwise
is growing at an annual rate of approximately 20%. such as cotton-polyester blends, where two different the result will be useless, as colours change
However, the proportion of textile production that Compared to a dye that is soluble, water-based ink types are usually necessary. markedly during drying and fixing. This setup work
uses digital printing is only about 3-5% up to now. pigment inks use an insoluble pigment to provide means that adding a new fabric or pre-treatment, or
The enormous fragmentation within the textile colouration of the textile. Compared to dyes the Colour Management changing an ink set, leads to additional work and is
process chain is a major challenge that make it pigments do not have a real affinity for special fibres, The colour management problem stems from the therefore a barrier to fast turnaround. Automated
nearly impossible to adequately assess the digital which makes them suitable for colouring on the top way that numbers are used to represent colour. The profiling systems alleviate this problem to a
opportunity for textile printing. The need for a layer of a various number of fibres as well as blends. colour of on-screen pixels is usually presented by significant extent, and so may be a worthwhile
so-called universal ink for all textile substrate and However, pigment inks represent only about 3% of specifying three values: a red, green, and blue investment.
accurate colour appearance is vital. inks used in digital textile printing. Inks most amount, making up the familiar RGB colour model.
commonly used are still based on reactive, disperse An RGB image is made of three greyscale images: Software designed specifically for digital textile
Need for Pigment Inks and acid dyes. one records the red channel, a second records the printing can address some of these issues, and also
The various number of different textile substrates green channel, and a third records the blue channel. to allow printers to use rotary screen and inkjet
ranging from natural such as cotton, wool or silk to While printing with reactive inks, the dyes need to be This is a simple way to represent colour, but printers in the same workflow and give similar results.
synthetic materials like polyester and blended fabrics bonded to the textile fibre after printing. Therefore, a unfortunately is completely ambiguous to actual This means that alternative production methods can
require different types of pre-treatments, inks, and steaming process is necessary. Subsequently, the colour appearance. Each device has its own idea of be considered depending on the run length, for
post-treatments processing. The ink types mainly unbound dye needs to be removed in a complex what constitutes the colour red (and green and blue). example. A design can be taken from the designer’s
used in industrial applications are reactive inks for washing process (after treatment) at different Different scanners and cameras produce different screen and split into separate versions for printing
natural fibres and sublimation/disperse inks for digital temperatures, followed by drying. In comparison, the RGB values when they are confronted with the same onto different output devices, for example a rotary
original or scene as they use different filter sets. screen printer using 8-12 spot colours, and an
Different monitors produce different colours when 8-colour digital inkjet printer. Sophisticated software
given the same RGB values as they use different can also enable the management of colour
phosphors or LEDs and filters to produce the colour. consistency across production sites in different
Hence, colour management is vital to match a countries, and allows correction for factory
colour appearance. temperature variations.

January/February 2018

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