Why Does Putting a Plastic Bag Over a Credit Card Work?

Have you ever wondered why placing a plastic bag over a credit card can sometimes enable it to work in a “tap and pay” mode but not in the swiping mode? This intriguing phenomenon is rooted in the way credit card readers and the magnetic stripes on credit cards function. Let’s dive into the details.

Understanding the Fundamentals

Reading a credit card typically involves two modes: tap and pay and swiping mode. The tap and pay method uses near-field communication (NFC) technology, which allows for contactless payments. In contrast, the swiping mode involves using the magnetic stripe on the back of the card to transmit information to the card reader.

Electromagnetic Waves and NFC

Plastic bags, being made of non-conductive materials, do not block electromagnetic waves. This is why a plastic bag can work in tap and pay mode. NFC technology relies on electromagnetic fields to communicate between the card and the payment terminal. Since the plastic bag does not interfere with these electromagnetic waves, the card can still function as intended.

Swiping Mode and Plastics

In swiping mode, the magnetic stripes on the back of the card are used to transmit data. A credit card reader contains a magnetic head that reads the information from the stripes. However, plastic is a non-conductive material that can snag on the magnetic head or interfere with the magnetic signal.

Blocking Magnetic Signals

When a plastic bag is placed over the magnetic stripe, it increases the resistance to the magnetic field. This interference can disrupt the magnetic signal, leading to garbled or unreadable data, which is why the card won't work in swiping mode. The plastic can also snag on the magnetic head, causing damage to both the card and the reader.

The Tight Fit Theory

There is a prevalent belief that the plastic bag somehow enhances the tight fit between the magnetic stripe and the reading head. While this theory has some merit, it is not the primary reason why a plastic bag can make a card work in some cases. The enhanced fit might be a secondary benefit, but it is not the primary mechanism.

Bank Recommendations

If you encounter issues with your credit card, it is best to contact your bank for a new card. Most banks have a policy for issuing replacement cards in cases of damage or when issues arise. Using unconventional methods such as placing a plastic bag over the card can lead to further complications and is not recommended.

Conclusion

In summary, a plastic bag can work with a credit card in tap and pay mode because it does not block electromagnetic waves. In swiping mode, however, the plastic can interfere with the magnetic signal and may cause the card to not function properly. It is important to keep your credit card in good condition and to follow official procedures for handling any issues.

For more information or assistance, reach out to your bank or a customer service representative.