Dye blocker

A dye blocker — also called a blocker base or low-bleed base — is a specialty plastisol laid down before the print colors to seal the fabric surface and stop the disperse dye in polyester from sublimating up through the ink film under cure heat. It's typically flash-cured around 260°F to 280°F on its own before the rest of the design goes down, and the whole print then cures at the standard 320°F for plastisol.

Printers reach for dye blocker constantly on 100% polyester athletic tees and poly-heavy tri-blends like Bella+Canvas's 3413, which runs roughly 50% polyester. Skip it under a white chest logo on a red poly jersey and the disperse dye can migrate into the ink within days, turning crisp white to salmon pink — a failure called dye migration. We've had a full batch of red-jersey tees come back three weeks after delivery for exactly that reason, no blocker under the white.

Spec a blocker base under any white or light ink going onto 100% poly or high-poly blends, and build the extra flash cure into your press schedule and your price — it's another screen and another 10 to 15 seconds of dryer time. Skipping it to save that step is the single most common cause of poly-garment print returns we see.

Any white plastisol looks like a blocker on press day, opaque and solid, so buyers assume it'll do the job on its own. Standard white ink resists dye migration poorly compared to a purpose-built blocker base, and the pink-out shows up weeks later, after the shirt's already shipped and worn — by then it reads as a garment defect instead of a missing production step.