Why grapes spark when you microwave them
When you make a grape flash, does it give a little whine?
It’s must-watch viewing for the science-curious: cut a grape in half with skin left on, pop it in the microwave, then wait a few seconds for sparks to fly and a bright puff of light, or plasma, to appear. A popular theory is that the hotspot creating the spark occurs because the skin conducts electrons back and forth.
But not so, suggest Canadian researchers in the journal PNAS. “The plasma is created due to an amplification of the electromagnetic field in between the grapes,” says Pablo Bianucci of Concordia University, Montreal. This is caused by the interaction of “trapped” microwaves. Skin or no skin, having two grapes, or two halves, is the key.