Plastic Bag Saves the Day!

I was suffering the embarrassment of an "invalid magnetic strip" at the grocery store-- for both my ATM card and my credit card-- and the cashier suggested I encase the card in a plastic bag and then slide it through the machine, and this trick worked . . . though when I asked why, she had no answer for me (better to ask this guy) and so the irony is that although I brought my own reusable cloth bags in order to save the environment (even though they may kill me because of the high lead content) it was a good thing that they had those environmentally awful plastic bags, or I wouldn't have been able to pay.