The Credit Card Plastic Bag Trick

Alejandro writes:

I was at the Key Foods by my house and as I was standing in line the lady in front of me swiped her credit card on the little machine by the register about three times with no luck. Then the cashier handed her a plastic bag and told her to wrap the credit card in the plastic bag and swipe it. I kind of laughed to myself, but the lady did as instructed, swiped the bag covered card and it worked. I must have made a face because the cashier smiled at me, and I asked her “how did you figure that out?” and she just smiled.

Credit cards store their information on magnetic strips. That means that if this trick is more than just retail voodoo, it must be aligning the card in such a way to make it easier for the reader to scan it. Which, you know, doesn’t make a lot of sense to us.

Anyone have any experience with this trick who might verify if and how it works?

Update: Good ol’ Cecil Adams says it’s because some readers are too sensitive and get hung up on little ‘spikes’ caused by scratches and the like. We’ll buy that. (Thanks, Dennis!))


Edit Your Comment

  1. That Guy says:

    Yup… I’ve used this trick before. I haven’t carried a wallet in years, so by the time my cards are due to be replaced, the strip gets all finicky from years in the front pocket.

    I think what happens is the strip gets ever-so-slightly worn down over time, and the additonal thickness of the bag presses it up against the reader for a snugger, magnetic friendly fit.

  2. DeeJayQueue says:

    Also a piece of clear tape does the same trick, and it’s reusable. I think i saw on Mythbusters that anything short of a degaussing magnet won’t erase the strip, but over time it gets cruddy and won’t read. The tape/bag/whatever keeps it from reading the dirt on the card.

  3. Jay says:

    When I worked at Banana Republic, we would use receipt tape instead of a plastic bag. Worked almost every time.

  4. Papercutninja says:

    Jay, you forgot about the good ol’tissue paper!

  5. Brian Drew says:

    I worked at a grocery store for two years in high school. It works just about everytime, I never knew why though. It just always did. We had a lot less success with tape though.

  6. Juancho says:

    Yep, all true. The speed of the swipe also makes a big difference. Making a swipe faster or slower will make it “jump” over the scratches/imperfections in the strip.

  7. MavisAncaeus says:

    The magnetic strip on your card is comprised of a large number of magnetic “ones” and “zeros” (magnetic highs and lows). Over time the magnetic particles in the “ones” of your card’s strip may get smeared over to the “zero” portions of your card. This will cause the scanner to read a one where it should be reading a zero, essentially causing the bad read. When you put a thin, non-magnetic spacer between the scanner and the card, it prevents the scanner from picking up the small number of misplaced magnetic particles. Toilet paper, receipt paper, dollar bills, and scotch tape all accomplish this.

    The strength of the scanner also impacts what techniques will work and if the scanner even gets a bad read at all. The stronger the scanner, the more likely it is to get a bad read and the less likely it is to be “fooled” into making a good read.

    Hopefully this will give more insight into the retail tom-foolery.