Colored polyester clothing is produced with a sublimation process. This means that the color pigments become gaseous when heated and penetrate deep into the fibers of the polyester. As a result, polyester also has a beautiful color and usually retains its color better than, for example, cotton. When printing, however, this way of coloring has one major drawback.
By reheating the polyester fabric with a transfer press, the pigments become active again during heating with a transfer press. We don’t want that, you don’t want that and especially the end user doesn’t want that. The active pigments can soak into the flex foil or transfer paper and eventually appear on the surface of the print, resulting in discoloration. We want to prevent this, right? The common thing about this discoloration is that it is almost never visible immediately after printing, but only becomes visible after some time. This varies from a few days to even a few weeks.
How do you prevent bleeding
Washing the textile has no influence on this! It doesn’t stop it, but it doesn’t promote it either. The result can then be a print that looks blotchy. Sometimes it is also described as a “fungus effect”. Of course this has nothing to do with mold, but it sometimes looks like penetrating damp or plastic that is “weathered in”. It goes without saying that the problem of bleed-through only occurs if you press a light print onto a dark colored textile piece, for example a white text on a dark blue polyester shirt. A dark print on a light shirt, for example a black print on a light blue shirt, is no problem. The problem can also occur with mixed forms of polyester with cotton. Roughly speaking, you can say that the lower the percentage of polyester, the smaller the chance that the phenomenon will occur. Although we also know examples of fabrics with 5% polyester that still bleed through.
The solutions are simple. Use a Flex that can be processed at a low temperature and then you have already ruled out the most risk of bleeding. This is possible with the 123Flex, the 123Premium Flex and the Poli-Flex Turbo. For extra protection you can choose the 123Premium BlockOut Flex, or the Poli-Flex BlockOut Soft. This is wise with thicker polyester fabrics such as Softshell.