Two metal bowls with metal decoration.
I didn't think about this while putting the first bowl in the microwave and starting the time. Grandmother turned around and poured herself a drink, but I saw the sparks. Luckily, they were just sparks. Part of me wanted to sit there and watch, but the other part knew that lunch was in that bowl.
I stopped the microwave and warned Grandmother. We found a non-metal bowl to heat the soup in. All was well.
Sometimes food does trump science.