CLEAN OVEN - Preheat oven to 150 and boil a pot of water. Turn oven off. Place 1 cup ammonia in baking dish on the top rack of the oven and the pot of boiling water on the bottom rack, close oven door and leave it overnight. Remove both but keep the ammonia. Remove racks air out oven for 15 mins. Wear kitchen gloves. Add 1-2 tsp dishwashing liquid 4 c warm water to ammonia and use heavy-duty nylon scrubbing pad to clean. Rinse.