Two Easy Ways to Clean Extremely Dirty Stove Grates
Try an Easy Household Ammonia Soak
Household ammonia is very inexpensive, and it will work to clean extremely dirty stove grates. The method is really very easy. Place each grate into a gallon size zipper bag, and add ¼ cup of ammonia to each bag. Make sure that it completely coats them. Turn the sealed bags over halfway through the day to ensure direct contact on both sides and in all of the nooks and crannies. Let the stove grates soak for at least 8 hours. For extremely dirty parts, allow them to soak for 12 to 14 hours. With gloved hands, remove the grates from the bags, and place them in a sink filled with hot soapy water. Dish soap that contains degreaser is the best option. Wash them with an ordinary kitchen scrub sponge. Anything that was stuck on should come right off.
Soak the Grates Overnight in Oven Cleaner
Oven cleaner contains extremely powerful ingredients that can easily cut through the toughest baked on grime. Contrary to popular belief, it can be used outside of the oven. It works exceptionally well to clean dirty stove grates. It might remove some of the shine, but when the metal is caked with baked on grime, achieving a clean surfaces is preferable to buying new parts. Take them outdoors in a well ventilated area, and place them in a trash bag. Spray all sides with heavy duty oven cleaner, and allow it to work overnight or for at least 8 hours. Rinse the oven cleaner off in a safe location. If necessary, use a scrubber sponge and a little cleanser to remove any remaining grime. They should come out clean, but in any case they should be clean enough to put back on the stove and use.
Sources: http://www.pinchingyourpennies.com/ and Professional Cleaning Experience