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Comments

Mike

Dude, welcome to 1998. I knew about this back when I was bagging groceries... When I was 15!!

Anon Ymous

Considering the heads of most scanners are spring loaded to ensure good contact and that the thickness of a grocery bag is about .8 mils, it hardly seems likely that the "added thickness" is what's at work here.

I've watched 15 year old baggers execute this with total confidence, but I'm still baffled by the mechanisms at work.

Anyone have a more plausible idea?

Aloysius

Ideas are always accepted... Even though this technique is known for some veterans back from 1998, I appreciate the one who posted it for others who don't know. Keep posting....

"Vidhya Dadati Vinayam..."

three_ace_six

It's nice and all but this dosen't explain how it really works.

three_ace_six

It's nice and all but this dosen't explain how it really works.

Adam, Salt Lake City, Utah

I have also known about this for years, but I assumed it had something to do with the tendency of plastic bags to build a static charge which amplifies the polarization of a worn out magnetic strip making it easier for the reader to pick up.

jim

i was a cashier at a local grocery store, and i used this trick often.

my explanation.

when the bag is opened it creates a charge... insert card. the electric from the bag charges the magnetic bar temporarily creating a electro magnet. magnetic field from bar passes though charged bag and bang it works.... lets just be happy that our "cards" do not use rare earth magnets

Dude_with_the_answer

If your credit card has this problem a lot, you should just place a piece of tape over it. It is the added thickness of the bag which causes the "magic."

Dave

Or you can call the 1-800 number on the back and ask for a new card!

Pat

This trick works because the magnetic strip gets worn down over time and might have small scratches in it and the plastic bag or piece of tape basically makes the strip "whole" again by putting a protective layer over it

Pat

This trick works because the magnetic strip gets worn down over time and might have small scratches in it and the plastic bag or piece of tape basically makes the strip "whole" again by putting a protective layer over it

Pat

This trick works because the magnetic strip gets worn down over time and might have small scratches in it and the plastic bag or piece of tape basically makes the strip "whole" again by putting a protective layer over it

Dan

Card readers can get 100-300 cards swiped a day... and some peoples cards are pretty messy. Really often your card will be fine all day - just that one store or just that one till. Wrapping something around the card, paper, plastic or what ever can help clean the reader head.

Julie

I agree with that last comment 'cept I can go back even farther than 1998 - let's see now, I belive the magstripe reader was introduced at check-outs in the '70's?
ha ha

Shad Bolling

The magnetic strip on the back of credit (and debit) cards can become slightly "smeared" over time. This smearing moves some of the magnetic particles away from where they were originally. Usually, this doesn't affect the data on the card, but the smeared particles can create small discrepancies in the data stream -- sometimes enough that a card reader won't read it anymore. When your card becomes this smeared, you should obtain a new card. While it won't work for very smeared strips, using a plastic bag separates the magnetic strip from the reader just enough that these small discrepancies in the data stream are averaged out. Essentially, it improves the signal to noise ratio.

ZERIC

Is there any one can do an experiment? Instead of wrapping the card by the plastic bag, just put a tape at the other side of the card. The tape can increase the thickness of the card, while do not change the surface of the magnetic strip. Let'ssee what will happen...

Dave D.

I was bagging groceries in 1953 and I don't have a clue what your all talking about.l

Curt Welch

I've had a card which worked fine on most readers, but failed every time at the local CVS drug store (even at different check out stations so it wasn't just one bad reader). They made it work using the bag trick at times. Other times I just paid cash to not have to deal with it. Later, we tried the tape trick. That made the card work on some of the bad readers, but stopped it from working on other card readers in other stores were it once worked fine. So there's nothing special about the bag, tape works fine as well. But it doesn't fix the problem, it just makes it work on some, but not others. So I wouldn't advice the tape trick - Just use the bag trick when it fails.

I think it's highly unlikely that was a fix related to cleaning the read heads. I also don't believe the static related effects could be valid. Static electricity on a plastic bag will not generate a strong enough magnetic field to play any significant role in the card reading. A static charge is NOT a magnetic field which is what the strips use to encode the data.

The theory I vote for is the one posted by Julie which suggests the added spacing helps average out the read errors caused by deterioration of the magnetic data over time.

The best solution is to get a new card which will have a fresh magnetic encoding of the data. The bag trick is great for dealing with the old card while you wait for the new one to show up.

Curt Welch

Ah, the comment I agreed with was posted by Shad Bolling, not Julie. I didn't understand the format of this message system.

Less Murphy

A more permanent solution is to put some Scotch Tape over the magnetic strip. It has much the same effect, and it'll stay there, unlike the bag.

Bob

Hey Nice Drivers licence sub for a Credit Card Smart guy!

denise zaharchuk

yes someone at the grocery store did this to my card and i used it at other stores then my bank gave me a new card and i don't need to do that anymore.so i would have to say that if you use your card alot or if it is older than it does work....

Jon

the easiest way, just grab a roll of scotch tape and slap a piece over the strip. takes care of the problem forever and it doesnt affect atm use.

Bob

Thanks to Curt Welch for testing the tape idea. Could I suggest that some readers are set too sensitive, and that extra spacing reduces the signal and avoids distortion? But on other readers reducing the signal makes it too low to read. That would explain why tape makes some readers better and others worse. The place this theory fails is that the bag trick seems to be used for older cards, which would be weaker already. -- Bob

Jon von Gunten

Removing an extra bag from the bag holder releases enough pressure on the stand to tilt it a few millimeters, propagating a torque through the floor and slightly twisting the card reader on the counter so it rubs more roughly over the mag stripe, thus increasing surface contact and the concmitant functional readability of the charged particles therein.

This seems pretty obvious to me. I don't see why you guys didn't get it a lot sooner.

The comments to this entry are closed.

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