Oven-Cleaner Ammonia Water Baking soda Preheat to 200° then turn off. In a heat safe glass dish, fill with ammonia and set on middle rack (about 1 to 2 cups of ammonia). In another dish, fill with boiling water and set on bottom rack (2 cups). Leave overnight. The next morning, remove dishes and wipe down the inside with a hot wet sponge first drizzled with baking soda.
Clean your oven overnight: Instead, place ¼ cup of ammonia into an oven-safe bowl. With the oven turned off, place the bowl in the oven and let it sit overnight. The fumes from the ammonia will soften any and all gunk in the oven, so in the morning, you can simply wipe it off with a clean sponge.