To shield EM radiation, there are the infamous aluminum hats. A colleague of mine actually tested that and found them to be ineffective as shields, because of the large opening downwards. Now I wonder if meshes are better than foils, because foils can actually reflect radation and a parabolic hat shape would focus incoming radiation right inside your brain. Meshes have closed loops which shortcut currents from induction. Is that better than foils? (Serious question on the shielding, mesh vs. foil, inserious with the aluminum hat example. Answers please on the mesh vs. foil part, not the hat part).