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Place 1/4 cup of vinegar, 2 to 3 tablespoons of baking soda or two halves of a lemon in a microwave-safe bowl. Choose one of the three options, not all three at once. Add 1 cup of water.
2. Microwave the bowl on high for five minutes or until the water is at a rolling boil. Keep the door closed for another 10 minutes while the water cools to a manageable temperature.
3. Open the microwave door. Remove the bowl and the rotating tray, if the microwave has one. Wipe out the inside of the appliance with a clean cloth. The steam from the bowl should have softened burnt-on food particles and lifted stains, and they should wipe off easily.
4. Look at the stains. If they are still visible, wet a cloth with the solution in the bowl, and scrub the stains with it gently.
5. Add water slowly to 1 tablespoon of baking soda to make a paste if stains remain. Spread the paste on the stains, and let it sit for four minutes. Wipe the paste off with a damp cloth.
6. Check the stains again. If you can still see them, open windows for ventilation, and put on rubber gloves. Wet a clean cloth with acetone. Scrub the stains with the cloth until they disappear.
7. Mix dish soap into some warm water. Dip a clean cloth into the solution, and use it to wash the baking soda and acetone out of the microwave. Rinse the inside with clean water, and dry it with a dry cloth. Return the rotating tray to the microwave.