You must buy "Low-Bleed" or "Poly" inks. Polyester dyes can "migrate" into the ink when heated; low-bleed inks contain blockers to prevent your white prints from turning pink on a red shirt.
Requires specific nylon-bonding inks or additives to ensure the print doesn't peel off the slick surface. buy plastisol ink
Standard or "General Purpose" plastisol is ideal. It offers a creamy consistency and easily mats down cotton fibers for a smooth finish. You must buy "Low-Bleed" or "Poly" inks