I'm printing with a polyester white ink, do I still need a blocker?
Every garment distributor has a list of ways and recommended inks to decorate the garments they sell. If you do not know, contact your vendor or the manufacturer and ask them what they have found in their testing
If you cannot get the information you need from in your searches, then the only way to know for sure is through testing and possibly feedback from other printers.
If you’re unsure and you do not have time to test, use a blocker base to avoid any possibility of dye migration.