What is dye migration you ask? Some of you may have had the unfortunate experience of having white lettering on a red 100% polyester shirt turn pink after a few weeks. This is because dye migration has occurred.
100% polyester shirts are colored using sublimation dyes and thus when you print onto the shirt, you will need a special vinyl with a BlockOut layer to prevent the sublimation dye from migrating from the shirt to your printed vinyl.
There are a large selection of colors out there that are either specially made with a blockout layer, or the pigments used have sublimation dye resistance. The most popular colors are available with a blockout layer and should be used when imaging polyester fabrics. For the colors that are not available with a blockout layer you should check with your supplier to ensure they are dye resistant prior to using.
The problem of dye migration may not always occur immediately after pressing. It may occur right after pressing or over a short period of time depending on the material and the color. However, there are tell tale signs that the shirt will have the problem of dye migration immediately after pressing. Here is a picture of the self adhesive backing sheet of a white vinyl after it has been pressed and peeled off of a 100% polyester red jersey.
As you can see there are traces of red on the backing sheet which means that the red dye will migrate to the vinyl if the vinyl is not dye resistant. (Note that if there are no dyes on the backing sheet after pressing the vinyl, it does not mean that dye migration will not occur.)
Luckily I used a white Blockout vinyl, so there will be no issues with dye migration! We recommend using blockout vinyl whenever you are dealing with 100% polyester clothing just to be on the safe side. It simply takes out the risk of dye migration.