If the upper platen of your heat press looks like it has seen better days, if it has residue of letters or numbers “burnt” into the platen or other undesirable remnants, you may want to follow these steps that I have published before, on how to clean your heat press.
If your press has a non-stick coating on the upper platen, you can usually clean it by letting the platen heat up and then rubbing vigorously with a rag, but you have to rub pretty hard, but it should come off (wear heat proof gloves or hand protection when attempting this). If your heat press doesn’t have a non-stick upper platen, you might have to use some light sandpaper or maybe a cleaner called GoJo, which has a light pumice sand in it, used in industrial situations or by car mechanics for removing nasty stuff from hands, or any other heavy degreaser with hot soapy water (of course when the machine is unplugged). If you use something with grit, such as Comet cleanser or Ajax on a non-stick platen, you can scratch the coating. If you don’t want to go to all this cleaning trouble, maybe you can try using a reusable cover sheet to protect your garments during application. Stahls’ offers a QuickSlip Pad protector to protect the bottom platen from stains and also make it easier to get garments on and off the lower platen. If your upper platen seems beyond help, you may want to consider ordering a upper platen cover from Stahls’ Hotronix. It is only available in the 16″ x 20″ size and you can find information on it on the Stahls’ Hotronix website.