Dye sublimation is the most versatile textile digital printing process and while it is not suitable for every textile substrate, it is certainly the best route for signage professionals to dip their toe in the world of printed textiles, and potentially other rigid materials with the same hardware. Here textile printing expert Magnus Mighall of R A Smart explains how.
Dye Sub, as it is affectionally referred to in the textile trade, utilises a textile disperse dye and is suitable for polyester or high polyester blend fabrics. Textile disperse dyes and dye sub have been around for a long time in the textile industry and disperse dye can be printed in a number of analogue printing processes such as flat screen, rotary screen, gravure or lithographic printing.
Disperse dyes can be applied onto a polyester based textile either ‘directly’ or ‘in-directly’ and both methods have pros and cons depending on the application. From years spent speaking to potential clients within the signage industry there seems to be an element of confusion around this, and it can often lead to costly mistakes made in terms of investment in capital equipment which may not be best suited for specific applications.
If you think textile printing is for you, the first thing you should do is to make sure you are talking to a systems vendor who fully understands textile printing and can fully explain the various production processes as well as all of the potential pit falls. For example, ’Soft Signage’ is certainly creating a bit of buzz around the signage industry at the moment and there seems to be a number of systems resellers jumping on the gravy train, and while printing onto textile is not quite the ‘black art’ it was once perceived as, there is still a learning curve that will require you to partner with a solid solutions provider who not only understands the process, but will understand where you are coming from and what it is you want to achieve. Therefore a partner that can ably demonstrate this and help guide a new user will make this a much smoother process.
Before you can print direct to textile with the disperse dye process you will first be required to apply a pre-treatment to the textile. This is primarily to help stop the spread of the dye on the textile and to hold detail, and on certain textiles such as knitted flag polyesters, the pre-treatment will also help in the draw-through of the dye to the reverse side of the textile, which is an obvious advantage when printing a double sided flag. A pre treated textile will be more expensive than a non pretreated textile of the same type, and pretreated textiles are not as widely available as non pretreated textiles.
After printing, the disperse dye has to be fixed to make the printed textile both colourfast and lightfast. There is absolutely no avoiding this process, it has to be done and there are no short cuts.
Fixation is most commonly achieved using a dry heat process for the majority of digital textile PSPs, although direct disperse dyes can also be fixed with high temperature steaming of the printed textiles. However, this process is normally left to those companies who are well established in textile printing. It is a lot more complex, but this can also have its advantages.
Fixation can be achieved either on- or off-line depending on your workflows. An integrated fixation unit is a space saving solution, and whatever comes off the printer is a fixed length of finished printed textile that is ready to be turned into a product. However, an integrated fixation unit is la lot less versatile and comes with an increased price tag, and it can potentially be less productive than with an off-line fixation system.
Because direct disperse dyes only require high temperature to fix the dyes (not both heat and pressure as with dye sub paper printing) the capital outlay for the fixation system can often be cheaper than a system required for the dye sublimation paper process. However, the printer element of the direct to textile system is most likely to be more expensive than a dye sublimation paper printer because the printer must be able to handle the textile media efficiently, and the faster the printer the more sophisticated the media feed has to be, because if not, the fabric will distort during printing thereby causing massive problems with image registration.
Having an off-line rotary heat press as a fixation unit provides greater versatility as this is suitable for both direct to textile and paper dye sublimation fixation, so it can service multiple printers, but this will normally come at an increased capital outlay
The other method of achieving high quality printed polyester fabrics is with in-direct printing with disperse dyes (paper dye sublimation), but this same process also opens up opportunities to allow printing onto a range of other media such as aluminium sheets, glass, ceramic including mugs and all sorts of other non-printables just as long as there is a suitable polyester coating on the material (and you have a flat bed heat press to accommodate the largest product you may wish to print). Dye sublimation on items such as coated aluminium rivals the print quality of UV printing, so this really can add to the range of products that a dye sublimation system can be utilised for.
As previously mentioned, dye sub paper printers do not need the media handling capabilities of direct to textile systems (although it is crucial that they can handle the dye sub paper in the correct manner), so they tend to be cheaper than direct to textile systems. What’s more, with dedicated dye sub printers now capable of printing high quality at 20 sq/mt hour starting at under £5,000.00 plus VAT, along with reduced ink prices, dye sub really does open up a world of opportunities for new growth areas for the signage printer.
Once the design has been printed onto dye sublimation paper, the paper (in mirror image) is introduced to the polyester fabric, or polyester coated product, on a suitable heat press. A rotary heat press will allow for lengths of textile to be produced without the restriction of a specific platen size of a flat heat press.
On most occasions the rotary heat press is the same maximum print width as the printer. Of course, narrower textile and sample/cut pieces can also be used through a rotary press and indeed, there are specialist rotary presses specially manufactured for additional versatility to allow production of roll-to-roll product, roll-to-piece product (printed roll of dye sublimation paper and cut pieces of textiles) or piece-and-piece production (cut dye sub paper and cut textile) with the latter systems tending to be used in sportswear and apparel applications.
Rotary heat presses are available to suit every level of production and a single rotary heat press can potentially look after the application processes from several printers. It is all determined by the drum diameter of the rotary press and the contact area around that rotary drum (not all heat presses available will have the same media path and offer the same productivity even if they have the same drum diameter, so it is certainly worth comparing when considering the best options to suit your business). The dye sub process requires approximately 40 seconds contact time on average for most polyesters fabrics, so generally speaking the larger the drum diameter the more productivity the press.
Lower cost rotary heat presses have an electrically heated drum, these have the advantage of being cost effective units as well as having fast heat up and cool down times, but they are not going to offer the same degree of temperature stability as the more costly oil drum systems, and as such this is a particularly important factor if considering a larger drum diameter or wider width press. Media tracking and maintaining correct tension as the substrate travels through the press is also extremely important and quality heat presses will have more sophisticated handling of both the paper and the textile.
Not only will an oil drum press have more consistent temperature of the drum but it will also be more efficient to run, and even though it will take longer to heat up, the oil heated drum will retain heat far better and consume less energy.
A suitable flat heat-press will open up the possibility of using the same dye sublimation printer to be used for printing onto rigid materials (coated with a suitable polyester coating) or potentially made up products such as t-shirts – all over dye sublimation prints onto t-shirts are now extremely popular and this is a very cost effective way of producing bespoke garment decoration.
Under heat and pressure the sublimation dye turns into a gas and is drawn into the polyester content of the material (the higher the polyester content, the more vibrancy of colour can be achieved) and dyes the fabric during the process. This normally takes anywhere between 30-60 seconds depending on the textile and processing temperature etc. Fabrics do not need any special pre-treatment for the dye sub paper process, so this also opens up opportunities of a wide variety of textiles to be used without the constraint of purchasing through specialist digital media suppliers.
Once the textile has been passed into contact with the sublimation paper in a heat press the end results are stunning. The print quality and colour vibrancy will visually ‘pop’ before your eyes. Other benefits of the sublimation paper process is there are no issues with wash fastness or colour fastness. This is because the disperse dyes used are not sat on the surface of the media as with most other processes such as UV printing, latex printing etc. which will stiffen any fabric once printed, but the dyes do actually dye the fabric causing them to become an integral part of the textile.
This has been a very short introduction into the dye sublimation process and hopefully has given sign makers an idea of whether or not dye sub might be something they want to consider adding to their service portfolio and how it might open up opportunities of additional revenue streams for new or existing customers
RA Smart has been involved with printed textiles for over 50 years and we understand the various processes required for different applications. We welcome both existing and new customers to visit to our facility in Macclesfield where we not only have a comprehensive demonstration suite, but we also have a production facility where we screen print textiles, dye textiles, weave textiles, and digitally print textiles. Therefore our visitors go away from a visit to RA Smart with a good appreciation of the world of printed textiles and what it can offer.