When it comes to printing on to textiles, there’s more to it than meets the eye. Fibres, dyes and colour is what it’s all about and getting all three right can prove tricky. Whether you are a wide format print service provider, traditional printer or sign maker you will have come across the term ‘digital textile printing’ and may have taken a step to the left to swiftly avoid this dark magic.
However, once you understand the basics you may be able to identify if digital textile printing creates an opportunity for your business, and if you understand how digital printing works then you’re half way there – the rest is chemistry.
Here’s my brief guide to digitally printing onto textiles.
You can break down the digital textile print process in many ways, but the simplest is by fibre, and this determines which inks/dyes you use to print. Fabrics can be broken down into the following main categories:
1. Polyester based fabrics
2. Cellulose fabrics based on plant fibres e.g. linen, cotton etc..
3. Animal fibre fabrics including wools and silks
4. Polyamides (for swimwear)
5. Mixed fibres e.g. Polycotton
There is also one other category that is not strictly “textile” in the traditional sense of the word, but I will include it here as it is growing in popularity amongst the digital print community and that is “non-woven” papers and polyesters i.e. wall coverings and media for latex printers.
1. Polyester fabrics (Disperse Dye inks)
Printing onto polyester is the simplest and most common digital print technique and the one most digital and wide format printers will be most used to. We use the term “Dye-sub” a lot in this industry and generally this is what is meant by sublimation. Flags, display graphics, exhibition and retail display fabrics are all printed using polyester based fabrics. Most of these fabrics are woven with polyester filaments, which means they are relatively rigid in the weave (non stretchy) and generally print without movement/skewing. Direct disperse inks are used to print polyester based fabrics and can either be printed directly onto the fabric or onto transfer paper.
If printing direct-to-textile, the fabric then needs to go through a heat process to “fix” the dyes into the fabrics. Usually this is done with a calendar (two-part process, print and calendar) but the very latest technology will allow you to do this in a one-pass process with the calendar in-line. Alternatively, the dyes can be printed on to transfer paper, and then transferred to the fabric, again through a calendar using heat to literally “transfer” the pattern from the paper onto the fabric.
In the wide format print and soft signage world, direct-to-textile printing with disperse inks and heat fixation is by far the most common way to produce textiles for display graphics, flags, interiors, displays, home accessories, bags, building wraps, theatre drops and more. The list is endless and business opportunities are growing fast as textile mills are developing vast ranges of polyester based fabrics to work with this print process.
2. Cellulose fibres - Cottons & Linens (Reactive dye inks)
Cellulose fabrics are based on plant fibres and include fabrics such as cottons, linens, bamboo and more. To digitally print effectively onto cellulose fabrics, Reactive dyes are required, followed by steaming and washing. Printing on to cellulose fabrics with reactive dyes is a time-consuming process but every step is important to ensure vivid colour and light fastness of fabrics. Cottons and linens are especially important to the fashion and interiors market. Short run digital print farms are starting to pop up around the world for interior and fashion fabrics and by far the most popular print process is using reactive ink dyes. Reactive ink will also print some wool/cotton or wool/linen and poly/cotton as well as silk/cotton mixes, but be aware the colours will not be as vibrant as 100% cellulose fabrics and you may not be able to colour match effectively.
In order to fix the reactive dyes, the fabric needs to be steamed ideally within 24 hours. Textile print companies usually print one day, and steam the next, so that the steamer is constantly in use and kept to temperature.
3. Protein fibres – Wools & Silks (Acid dye inks)
Generally thought of as a highly skilled textile print process, and certainly one of the most expensive, is silk printing. Thanks to new technologies however, digitally printing onto silk has become accessible only in the past few years. Silk printing was invented back in the early 19th Century when Acid dyes were first developed. Back then they used blocks to print fabrics, followed by screens and now we can use digital textile printers.
The main reason why printing on to protein based fabrics is more expensive, is partly due to the nature of the fabric itself being more expensive to produce (i.e. feeding livestock for the raw materials to then process and spin into fibre) and also because of the pre- and post-print treatment of the fabric including coating, steaming and washing needed to fix the dyes (longer than other processes) and stentering for the final finish.
The UK is thought of as having one of the oldest, and most well respected silk printing industries in the world outside of China. The silk industry in the UK had a blip in the late nineties with low-wage countries competing at very low margins, however with the increasing demand for quick turnaround, low volume printing, the industry has revived. Digital printing especially has helped enable this resurgence and the re-shoring of silk printing back to the UK in recent years.
Printing on to wool is less common simply due to the nature of wool and its tendency to rub or ‘pile’. However loosely woven wool based fabrics such as Wool Delaine is widely used for scarves and clothing.
4. Polyamides (Acid dye inks)
Polyamide fabric is used mainly for swimwear and is extremely stretchy. Any print on to this fabric needs to be robust, colourfast and be able to withstand numerous washes and heavy usage (i.e. chlorine and UV rays). Printing effectively onto polyamides has been extremely difficult and certainly small run has been nigh on impossible until digital. Accurate pre-coating is essential to reduce the chances of the textile ‘grinning’ i.e. showing white lines when the fabric is stretched – a common problem with transfer printing.
However there are some manufacturers now that have created machines aimed squarely at this market and are doing well.
Once printed, the polyamide fabric is then steamed and washed to finish.
5. Pigment inks…
Pigment ink is kind-of in a class of its own. With all other dying/ printing processes, the ink dyes are absorbed in some way and become part of the fabric. With pigment printing, what essentially happens is the ink/dyes are accepted on the top fibres of the fabric, without deep penetration, and ‘baked’ in. As a result, pigments can be used on almost any kind of fabric on the market today, including naturals. You just need the ink/dyes to ‘bake’ with a dry heat and you’re away – no need to steam or heat fixate at the higher temperatures associated with disperse or acid inks and no washing required.
Also, generally, you don’t need to pre-treat the fabric so it’s possible to print onto cheaper, uncoated fabrics. Pigment printing is seen as a quick, easy and uncomplicated way of printing onto a wide variety of uncoated fabrics digitally and this is the main reason why it’s so appealing to the wide format print industry.
So why isn’t it more popular in the textile industry? Put simply, in traditional terms it’s seen as the ‘easy’ way to print. With pigments, you will find it hard to get an accurate result in terms of colour matching and the colour gamut is small compared with reactive or acid – it has a “chalky” effect. Neither will your fabrics have the durability expected for, or pass a rigorous ‘rub’ test on, fabrics for interior accessories (like furniture for example). Pigment printing however is seen as the next “big” thing to hit the sign and display market and in most interior and homewares applications, is very acceptable.
Though this article was quite technical, I’ve literally only just given a brief outline of the basics of fabrics and dyes/ink types. But I hope you’ve found it interesting and it has help set the scene for you as a digital printer in terms of digital textile printing, and how it may or may not fit into your existing print plant.
Media and fabric manufacturers are finally starting to take note and are designing new fabrics specifically for digital print. Most notably polyester fabrics for disperse dye-sub printing and wall coverings for latex inks.
It’s exciting times as now we have a range of products that are affordable and widely available with skilled technicians with an understanding of the digital market place and all that it demands.
And that in itself, is all about chemistry.
Berni Raeside-Bell is a well-respected public relations and marketing professional in the wide format print industry. Her career began selling Apple Mac’s and RAID arrays at Jigsaw Systems, moving on to become the first marketing manager at UK wide format printer distributor Art Systems, seven years later leaving to found specialist wide format print PR and marketing agency BRPR, independently working with manufacturers and resellers of wide format print and imaging equipment for over 12 years. Having graduated in 2014 with a first class honours degree in Textile Design, specialising in Print and Knit, Berni is now positioned as one of the few professionals in our market with this unique mix of specialist knowledge. She has written for a number of specialist print publications and has given talks at numerous print trade shows and exhibitions.