By Jos Notermans
The technology of digital printing on textiles offers a lot of very attractive advantages, such as an unlimited amount of colors to be used in a design or the absence of a repeat. But it also has its challenges. Among those is the issue of through-print. For items like flags or fashion scarfs, it is desired that the image is visible on both sides of the fabric in an (almost) identical density.
In traditional printing this is hardly an issue, and very satisfying results are common practice in the industry. But it’s quite different for digital textile printing. The inkjet technology used to print directly on textiles is a non-impact printing technology, which means there is no contact between the printing device and the fabric. Ink droplets are sprayed on top of the fabric, and not pushed into the fabric as is done with a rotary screen. Even in digital sublimation printing, no satisfying results are achieved because the amount of ink that is laid down on the sublimation paper is simply not enough to transfer through the fabric, even if it is pushed onto the fabric in a kalander.
The actual digital printing through-print has two major drawbacks: first, the overall through-print is not enough, and, second, it is not evenly distributed. Dark colors will penetrate some, but light colors don’t penetrate at all. The image on the backside of the fabric looks like a faded version of the front side and a very reduced image.
Simply putting more ink down is not a solution, as this leads to a stark reduction of image sharpness because the inks will start to bleed over the fabric. Therefore, Stork has patented a special fluid that is put on the fabric with an inkjet printhead (patent number WO 2008/010705 A1). So, instead of using the normal eight ink colors, only seven colors are used (normally gray is taken out) and replaced by this special penetration fluid. A special calibrated profile in the printing software is used to determine for each pixel in the image what amount of penetration fluid is needed to make every ink density penetrate in the same amount through the fabric. This unique solution gives a much better result in the overall density of the backside image and in the correct color tones in all densities.
The solution is currently available for disperse inks, to print on polyester, and for acid inks, to print on silk for scarves and other fashion items.