Here’s a question: what is dye migration? You’ve heard of it, maybe you’ve even experienced it. But what really is dye migration, and how does it affect your garments? Let’s talk about how dye migration occurs and how you can prevent it from happening on your next job.
WHAT IS DYE MIGRATION?
Dye migration is defined as movement of dye from a dyed material (like the threads in a t-shirt) to another material in contact with that shirt (like ink). This means that the dye from polyester fabric is moving—or bleeding—into the ink printed on top of it. Bleeding can happen at different stages. If you notice bleeding right after the shirt finishes curing, that is called dye sublimation. If a garment bleeds over time, that is dye migration. While these issues are a little different, they have the same solution, and many screen printers use the term “bleed” or “dye migration” to refer to both issues.
This process occurs in polyester and poly/cotton blend shirts. Any fabric that includes polyester—no matter how small the amount—will be affected (polyester garments, triblends, 50/50, and even 90/10 polyester ratios). White polyester, however, won’t experience any dye migration, because the polyester fabric has no dye.
When a garment is heated to anywhere between 260°F and 340°F, the heat causes dye in the garment to sublimate. Sublimation occurs when something—in our case, the dyes used to color polyester thread—moves straight from a solid state to a gaseous state. This will change the color of the plastisol ink you used, because the dye color of the shirt has moved into the ink. While water-based ink does experience dye migration, the process occurs a lot quicker with plastisol ink.
Pro Tip: The hotter the dye’s set temperature is (meaning the higher temperature that the dye was set at), the more expensive the shirt is. The less expensive a shirt is, the more dye migration you’re bound to notice.
HOW TO PREVENT DYE MIGRATION
So dye migration is bad. How do you stop it from happening in your shop? Here are some tips to combat migration in every part of the screen printing process.
BEFORE YOU PRINT
Before any printing starts, do research on the garment you’re going to use. Look it up on the vendor website. The vendor may have recommendations for printing. Since the vendors themselves do testing on the garments, they’ll have a great idea of what you’ll need to do to stop dye migration.
Listen to feedback from other printers. The screen printing community is competitive, but also can be a wealth of information for you. Head to forums and Facebook groups to ask questions, get advice, and check out feedback from other printers who will have helpful tips.
Use high-quality dyed shirts. Poly and poly-blend garments are most at risk of dye sublimation, and the cheaper shirts you buy, the more likely you are to experience dye migration. Make sure that the polyester or poly-blend shirts you’re using are high quality.
When printing on poly or poly-blend shirts, selecting the right ink for the job is important. A low-cure ink like FN-INK™ will help, but doesn’t completely solve the problem. You can also print a low-bleed white underbase, or print with a poly white ink.
The best way to make sure your garments don’t experience dye migration? Print a blocker base like FN-INK™ Barrier Black. It’s a specially made ink designed to stop dye migration on polyester garments from the bottom up.
It’s important to lay down a thicker ink layer when printing with low bleed or dye-blocking inks. Having a large volume of dye-blocking ingredients is necessary when it comes to stopping stubborn, unruly polyester fabrics.
Once the Barrier Black carbon blocker base has been printed, gently flash the ink layer. Since it’s a black ink, it will absorb heat and infrared quickly. Proceed with either a print-flash-print of the FN-INK™ Barrier Black or with the rest of your design.
When curing ink on polyester garments, it’s important not to overheat or over-cure the ink. The longer the shirt is under high heat, the more likely you’ll see dye migration. “Low and slow” is the optimal way to fight dye migration. Think of it like a good barbeque.
Another factor to take in mind when fighting dye migration is to not stack your freshly-cured shirts. Some fabric dye is very sensitive, and the chemicals in your inks can cause a ghost image to appear on the shirt.
A tiny amount of the active ingredients in low-bleed and poly white inks can damage the fabric. This is less common in low-bleed whites, but can still happen in poly white inks. In addition to this, some inks used in printing on polyester contain peroxides. These peroxides usually gas out in the dryer —if you’re going low and slow enough—but if you stack your shirts right after they’ve come out of the tunnel, they can still off-gas into other shirts. This can leave a ghost image on the shirts they’re stacked on. Make sure to leave your shirts in the dryer for longer and at a lower temperature, and try to avoid stacking them right after they come out of the tunnel.
Testing is important any time you print, but vital when printing on poly and poly-blend garments. You want to make sure that everything is as dialed as can be before you head to production. It’s always better to experience dye migration on a test shirt than on a customer’s shirt.
Practice makes perfect when printing on polyester materials. Understand your tools and how to make adjustments based on what you see during testing. You can avoid dye migration by knowing the shirt you’re using and taking preventative measures.