When you remove shrink wrap, you should remove it very slowly and gently. Be sure to always wear gloves while doing it because the shrink wrap needs to be removed while the tumbler is still hot. The reason you would do it slowly is because the shrink wrap is plastic and will stick to the coating as it melts, so when you take it out of the oven it hardens on the cup, usually on the bottom and top of the cup. You may also use masking tape, but only the white one. The white masking tape has less adhesiveness so there is a smaller chance of it getting on the sublimation coating. If it does get on the coating, simply clean it off with some rubbing alcohol.