Sublimation blanks.

A sublimation blank is a substrate carrying a polyester or polymer coating for the disperse dye to dissolve into, which is the whole difference between a sublimation mug and a mug. JPPlus states the requirement plainly: sublimation blanks need a polymer or polyester coating, and on fabric the target is 100% polyester or at least a 65% blend. An uncoated ceramic mug, bare aluminium or plain glass is not a blank; it is an object you would have to spray with a sublimation coating first, and a sprayed coating is not the same product as a factory-cured one. This is where the drinkware and hardgoods half of print on demand actually lives, and it is also where blanks get bought on price by people reading the word mug and not the word coated. The fault shows at the press, usually on a personalised run with a different name on every piece, so it is the whole job that reprints rather than one line of it.