microwave only. wire meshing and all that.
Google it.
but forget the other ideas. Do they emit radiation or microwaves? No! then stick with the idea that make popcorn but doesn’t fry whoever is closest.
Omigosh. Such ignorance being propogated on FR. People, please stop telling people to use old microwaves for Faraday cages for EMP! I'm telling you this as an RF and microwave engineer with over 20 years experience. Just because you think microwave ovens don't "fry whoever is closest" with "radiation" (oh my, your Wifi which operates on the same freqs would be horrified) doesn't mean it's a good shield for the VERY WIDE band of frequencies emitted by an EMP bomb or even a solar event.
Please, just put stuff you want to protect in a closed metal box with a tight-fitting metal lid. No mesh, no open spaces, no nothing.