There’s foil in my wallet

But I’m not crazy. The foil is only there to block the scanners. The bank sent out the new credit card a while ago, and it has a chip in it. After reading about the potential risks, it seemed like some shielding wouldn’t hurt anything. But how to know if the shielding worked?

At one work site, I get access to the facility by putting my id card against a scanner. This works even if I just hold my wallet up to the scanner. This seems like a reasonable basis for testing. The first thing I put in my wallet was a piece of what seemed to be metalized paper from a coffee package. Holding up my wallet still activated the door, so a coffee bag probably will not block the scanners the men in black would carry if there were men in black following me.

Next time I went out to that site, I folded up four layers of regular aluminum foil and put that in my wallet. The scanner didn’t work. A week or so later I tried it again, and this time scanner did read my card through the foil. Thinking it might be because the foil had compressed, I opened up the foil and interleaved a piece of paper. My knowledge of electricity and magnetism is close to the cargo-cult level, you see. Anyway, this seemed to work, but I’ll test it again from time to time.

If I come across some sheet copper I’ll try that too. A couple of business-card size pieces of copper with the Lord’s Prayer engraved on it would probably excite less interest than a packet of aluminum foil.


4 Replies to “There’s foil in my wallet”

  1. It might be the unevenness, too– microwaves can actually take metal in them, it’s just when it’s got something the power can spike at that it’s an issue. (highly simplified)

    So a metal card with words cut out of it would probably work very nicely.

  2. The metal foil might be producing some interference, but that’s not a reliable way to prevent the reading. What you need is a Faraday cage–an unbroken conductive surface around the card.If you put the card inside the foil and the foil has good contact with other foil all around the edges, that should do it. Or you can buy one of those special metal wallets designed for this purpose.

    1. I’ll try that. Initially wrapping it in foil seemed like it would take up too much space, but what I have now is two layers of foil around a piece of paper, so if anything it will take up less space.

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