How to Use Glass Paint Marker Shake well. Clean surface with glass cleaner before applying. To activate, press down on tip until color appears. Allow painted project to air cure approximately 8 hours. For a dishwasher-safe finish on oven-safe surfaces, place finished piece in a cool oven, set temperature to 325°F, bake for 30 minutes, then cool with oven door partially open. Not for direct contact with food.