Image Armor explains how to use its new E-Series direct-to-garment inks to print white ink on black 100% polyester fabrics with no dye migration and superior washfastness

Historically, there have been serious dye migration and wash issues associated with printing white digital ink on black polyester fabrics, but not any more. Using its new E-Series direct-to-garment inks for Epson re-purposed printers, together with its Ultra Formula pretreatment, Image Armor has developed, and is perfecting, a print technique that will make the digital printing of white ink onto black polyester a production oriented process that can be implemented by any D2G print shop. Brian Walker, president of Image Armor, explains how it’s done…

1. The shirt

Pick a good polyester shirt. We used the Sport-Tek ST340 – a cationic dyed polyester shirt, which has been dyed at a lower temperature so there is less dye migration during heat curing of the printed ink. We are currently testing other polyester shirts and dye processes.

2. Pretreating

We applied 32 g of Image Armor Ultra pretreatment – you could use higher amounts, up to 40 g – and set the heat press to 185°C / 356°F. We used only enough pressure to ensure minimal ‘contact’ between the platen and shirt, which meant that the pretreatment took longer to steam off and dry: expect to do two 30-35 second presses compared with the standard 35-40 seconds. Use a cover sheet during pressing, but avoid Teflon – it can add a shiny finish to the polyester fabric. Using too much pressure will create a heat press mark, which won’t wash out.

When you pull the shirt off the heat press it may be extremely stiff: it will regain its original fabric feel after it has cooled down.

(Left) A close-up of a D2G print onto 100% polyester fabric using the new Image Armor E-Series inks. (Right) The same print after six wash cycles: there is minimal degradation of the colours or print

3. Printing

The printing process is relatively straightforward; however, some printers and RIPs may be better suited for printing white ink on polyester fabrics than others.

The objective is to lay down the maximum amount of white ink on the first pass for the underbase. Your printer and RIP will dictate the actual amount – for example, the Epson Pro series printers allow you to deposit less ink compared to an Epson 3000 printer. It is essential to do independent testing with your own printer and RIP.

Compared to a 100% cotton shirt, a polyester shirt will require 1.5- 3 times the white ink. However, laying down too much white ink can result in the white ink not being kicked over enough. In this case, when you heat press the CMYK ink it will blend into the white causing a dulling of the image and a degradation of the image clarity. Again, testing with your own equipment is essential.

Avoid a heavy deposit of white ink on the second, or highlight, pass. All the pretreatment will have been used up on the initial deposit of white ink, so printing more white ink will result in a serious wicking of moisture and components from the ink into the surrounding polyester fibres. The ink will either spider out or create a halo around the image, which may or may not wash out after printing.

The new E-Series inks from Image Armor

You may also get this halo effect when depositing a lot of white ink on the underbase, however this will usually wash out in the first wash and is most noticeable on lighter coloured garments.

When loading the shirt thread it onto the platen. If you’re forced to lay the entire shirt onto the platen you risk ink passing through the first layer of the shirt and depositing onto the inside of the back layer. You could use a slip sheet between the shirt’s layers; however, the ink will soak the paper, which can cause it to swell and possibly bubble up, raising the surface of the shirt and risking a head strike.

4. Curing the ink

The Image Armor E-Series inks cure at 185°C / 356°F for 35 seconds. The shorter cure time is an advantage when working with polyester fabrics. However, you have to consider the large amount of white ink deposited and the much lighter pressure on the heat press when printing polyester: use a cover sheet and after 35 seconds lift it to let any moisture escape. You might also want to try two 20-second presses.

If you put your hand over the print just after releasing the heat press and you can still feel moisture coming off the print, it most likely is not fully cured or dry. You will need to ensure a full-cure, otherwise the print will start flaking off after just a couple of washes.
We have not tested ink cure through a conveyor dryer at this time, but we have found that hovering a heat press does not work particularly well: the inks will try wrapping around the fibres leaving cracks in the colours resulting in a less than desirable print.

Red and maroon polyester fabrics still tend to suffer from dye migration during the curing process and even after the cure has been completed. Image Armor is now engaged in tackling this particular challenge.

We recommend washing the garment prior to wearing it and, as with any D2G printed garment, allow the ink to cure for at least 24 hours prior to washing.

Making it all happen

We have achieved really good results printing the E-Series inks on black 100% polyester fabrics. Some prints look as good, if not better, than screen printed designs, and could easily pass for standard screen prints. There is still a lot of work to do to perfect this approach, but we are making great strides in developing an industry wide, easy to accomplish process.

Image Armor E-Series direct-to-garment inks are available from UK distributors, J&B Sewing Company.

Brian Walker is the president of i-Group Technologies, Image Armor’s parent company. i-Group Technologies manufactures the Viper range of pre-treatment machines for direct-to-garment printing, along with Image Armor pre-treatment products and new E-Series direct-to-garment digital printing inks.