Not arguing, just sharing proven science.
Here is a diagram of a basic test set-up. Using an anechoic chamber (so we know there are no other signals present), we can radiate a known power level of radio frequency (for our purposes lets go with 10 V/m) towards the styrofoam, and we can measure anything that passes through with the receiving antenna. This will tell us exactly how much of the RF is being blocked/absorbed by the styrofoam.
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No black magic, no voodoo...just using confirmed science to prove out your theory.