Originally posted by Digitalis it acts like a Faraday cage and cuts off transmissions
And if you turn on the microwave oven it leaks enough microwave radiation to jam a wi-fi connection even if the phone is only in the near vicinity. All I have to do to disrupt my wife's Facetime with our kids is heat up a cup of coffee in the microwave. Almost all cellular frequencies have longer wavelengths than a microwave oven, so they shouldn't be able to penetrate inside the oven, suggesting that putting a cell phone inside a microwave oven will be just as effective as putting it inside a copper lined pouch (which you can purchase on Amazon, of course). Of course, turning the oven on while a phone is inside should produce a little light show with smoke effects, but requires frequent replacement of the cooked phone.