The oven cleaning is among the most cumbersome tasks in the kitchen: chemically, fatigue, rub, discomfort and the result is often disappointing. But not anymore!!! Just yesterday I learned how to clean the oven, without any trouble, without chemicals and with minimum cost. With a single application, The oven was as good as new. From radicio.com
Here's how:
ingredients
1 water pot
1 sachet ammonia (that we put into buns)
Method
Put the pot of water to boil. Remove from heat and add ammonia. Put the pan in the oven in the kitchen (with grills, to clean and these) and close the door. If our oven has vapor extraction system, just throw a towel into the opening. Allow the pan in the oven overnight. In the morning remove the pan from the oven and wipe with kitchen paper towels or oven and grill. That's all. The burned fat leaving a simple wiping. 
If the oven is in very bad condition, you may need a second application
