Heat the surface of the appliance, either by turning it on in the case of a cooker or hot plate or by warming it with a hair dryer or other heat source. When the appliance warms up, scrape as much of the rubber off the appliance as possible using a butter knife or spatula. Turn off the heat source and allow the appliance to cool down.
Add a drop of dish soap to a spray bottle and fill it with warm water. Spray the burnt rubber with the spray bottle solution. Wait 30 minutes for the dish soap to work into the rubber. Scrub the burnt rubber marks with a soft-bristle scrubbing brush. Clean the foam and suds away with a damp sponge.
Put a tablespoon of baking soda in a cup. Add a couple of drops of water. Mix the water and the baking soda into a paste. Rub the paste over the remaining burnt rubber marks with a damp cloth. The slightly abrasive baking soda will clear away the last of the rubber. Clean the appliance with the damp sponge.