What is arcing and what causes it?

Arcing is the microwave term for sparks in the oven. It is caused by metal or foil touching the side of the oven, foil that is not molded to food (upturned edges act like antennas), metal such as twist-ties or poultry pins, and recycled paper towels containing small metal pieces. If you see arcing, press the CLEAR/OFF pad and correct the problem.