The basics of textile Digital Print
by Maria José Leaño

The idea of using Digital Print for decorating fabrics has always fascinated me, and now that I am able to work with it I have realised how little people know about it and how little it is being applied in the textile industry. If you try to find digital printed garments in clothing stores you will be amazed that it is difficult to find enough examples and that the quality and the designs are not especially good, it even looks as if it is a very cheap printing method. The truth is, textile Digital Print is very expensive und probably because of that, almost unknown – one of the reasons why the industry has not yet invested in the development of good design for it.

About ten years ago, I only thought about using this new process as a replacement for silk-screen printing. At that time, I helped to develop a software system for making strike-offs.

Digital print on paper using sublimation dyes for transfer on polyester. Design based on macro photography

I had just finished my studies in Textile Printing and had had my hands on some software packages developed for that purpose. It was the time when laser engraving started becoming very strong, so the logical procedure was to scan huge designs, create repeats, make colour separations to prepare the files for screen engraving and use them in Digital Print to simulate colourways on paper using big ink-jet printers (wrongly called plotters because of their size and form). This was, of course, not the right solution for the textile industry. The clients wanted to see fabrics, and even if they accepted the samples on paper, they where not happy with the fabrics afterwards because they looked very different from the original samples on paper. There were many problems to be solved, starting with the costs of equipment such as large scanners, printers, laser-engraving machines, inks and paper. So why not print directly onto fabric to create the strike-offs or even go further and actually produce the fabrics?

Many ideas have been developed to date, and many problems are still there to be solved, but now it can be said that Digital Print works and that it is possible to produce fabrics using it. The three principal technologies that I consider important are: direct printing with reactive and acid dyes, transfer printing with disperse dyes (sublimation) and direct printing with pigments.

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Acid and reactive dyes

Used for direct printing on natural fibres such as cotton, silk, wool, nylon (acids only) and some cotton/polyester mixtures. These dyes provide the ink maker with the least difficulties in that they are water-soluble. The complexity of this process shows how difficult it is to transfer a common printing process to a digital, computerised one. The inks developed for this system contain basically water and dyes; the rest of the components needed to fix the colour and to avoid bleeding are added to the fabric before printing. Once the design is printed, the fabric is left to dry, then steamed and washed. Dyes with very good fastness are required in this process.

Transfer print with disperse dyes (sublimation)

This system has the advantage that the colours do not have to be printed directly on fabric but on paper. The process itself is very simple: the design created on the computer is printed on transfer paper using sublimation dyes; the paper printed in this way is run through a calander together with the fabric. After this process, the colours are fixed to the fabric, no post-treatment is necessary. Polyester (PES), polyamide (PA 6, PA 6.6), polyacrylnitril (PAN), triacetate (CTA) and woven fabrics with 60% of the named fabrics are suitable.

The final product has brilliant colours, is wash-proof, UV-proof, scratch-resistant, chemically stable, and does not irritate the skin. The production is environmentally friendly, does not require a solvent, and does not create any ecological problems.You can sublimate fabrics, metals, ceramics, carpets, ski- and snowboards, imitation leather, plastics, tapes and much, much more…

Direct print with pigments

Pigments are molecular aggregates, insoluble in water; they have no affinity for the fibre and their fixation in printing is achieved by the use of a binder, which encloses them and provides a bond between them and the fibre. Therefore, the inks using pigments for Digital Print contain not only the colours, but also the binder to fix them to the fabric. After printing, the colours only need to be fixed using hot air, which at the same time irons and dries the fabrics, a very environment-friendly process.

Besides its easy fixing, this process has many advantages over the other two mentioned. One of them is the possibility of printing on mixed fabrics, used mainly on household textiles. Using a pigment printing system is also the only way to print matt white on colours and metallic effects (processes that haven’t been developed yet, but are being tested already).

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Summer dress made with digital print on silk. Design drawn directly on computer using a commercial drawing program
Direct digital print on cotton using reactive dyes; detail of a kimono. Hand-drawn design, scanned with drum scanner

The equipment

Pigments and disperse dyes must be prepared with a high degree of expertise. They are not water-soluble and only exist in water as a dispersion of small particles that can settle or agglomerate, closing the ink-jet nozzles. Because the dyes are very sensitive to temperature changes, only piezo printers are being used. A common colour-matching software can be used. An extra step-and-repeat function is recommended for covering a surface with a repeated design, but remember, this idea of printing fabrics repeating a master belongs to silk-screen printing.

Whether transfer, direct or pigments, the printing system to be used should be chosen depending on the end use of the fabrics to be printed.


The designs

Many textile designers already work already using computers to speed and improve their work. Most of them are still using the traditional processes, because they either do not believe in computers or do not want to learn to use them because they survive well without them, which I respect. In my case, I have been working with computers since I started designing professionally and could not imagine designing without them. In the beginning, I used computers for supporting my handwork; today I work the other way around, using hand painting to support my computerised designs. The results are amazing; a digital camera has also influenced my work a lot.

There is also a big difference in designing for traditional rotary screenprinting and for Digital Print. Now it is not necessary to think about colour separations or to limit the size of the repeat to the size of the screen or the cylinder. But because almost everything is possible, quantity is winning over quality. This aspect will be covered in a future article.

Published at "Eurostitch", 12.2004