For post-press only, please! Using a teflon sheet during the first press may cause your transfers to apply incorrectly. Adding teflon sheets or bonnets between the heat platen and the transfers during the first application may impact the amount of temperature you're getting, up to 30˚F! Using a Teflon sheet voids our replacement warranty because the transfers will fail due to improper application.
The only time we recommend using a teflon sheet is when you're post-pressing - usually to add a gloss finish to our DTF heat transfers.