Eelskin Wallets

I mentioned the findings in Cecil’s column on eelskin wallets to a co-worker

(the column is here: http://www.straightdope.com/columns/read/906/do-eelskin-wallets-demagnetize-bank-teller-cards)

Aha! Tested by actual experiment!
My co-worker replied that Mythbusters had done the same thing and declared the myth busted:

From the Wiki entry on this episode:

The implication is that you wouldn’t encounter magntic fields strong enough to demagnetize your cards, and it’s elsewhere stated that they had to find one of Jamie’s neodymium magnets to wipe the card.

But Katie of Citicorp’s in-the-wallet magnet was capabvle of wipin cards from 2" away!
Did anyone ever find out why such humongous magnets were being used?

Wallets that are stuffed enough to want a clasp in the first place tend to expose that clasp, in actual use, to all sorts of shear and torque. If the magnet is to be useful, it has to be quite strong.

By the way, a hagfish is not an electric eel, but neither is a hagfish or an “electric eel” actually a member of the eel family. These days, hagfish usually are not even classed as proper vertebrates. However, they, like the electric eels, have a generally eel-y appearance.

Wikipedia remarks that the hagfish are generally the winners of “most disgusting aquatic lifeform” competitions.

Yer muissin’ the point – the magnets used by the Mythbusters guys were strong enough to keep the wallet closed, presumably, but not styrong enough to wipe the magnetic strip, even up close. The wallets tested by Citicorp, on the other hand, were strong enough to wipe the cards from 2" away. Clearly, there’s something odd about the bunch Citicorp tested. Or the ones Mythbusters tested were weak.

I’m familiar with lampreys and hagfish, but I didn’t realize how incredibly gross they were until I saw Mike Rowe dealing with them on an episode of Dirty Jobs. They ca n produce truly prodigious quantities of mucous. Yecch.

This table shows the magnetizing field strengths necessary to erase various types of media, all of which can be easily reached by neodymium magnets.

The discrepancy might be because the Mythbusters-team used high coercivity magstripe cards, if the Citicorp folks used low coercivity ones (though, actually, both still ought to be deletable by neodymium magnets, at least at close range – wikipedia quotes them at 13,800 Oerstedts for an intermediate strength, while even high coercivity cards can be erased at 4,000 Oe, so maybe Mythbusters used weaker magnets as well).

Eh, I think I misread your question. Is there any indication that the eelskin wallet clasp in question was not a neodymium magnet? They’ve become reasonably common, in everything from children’s toys to a pair of strange curtain pole holders (or what appeared to be something similar) I found on my desk one day.

But the eelskin itself isn’t to blame. It isn’t that eelskin conducts static electricity or magnetism differently than other wallets … it’s just a myth because of the mis-observation of people who were expecting it or looking for it. Probably observation bias, reporting bias, and other flaws in the study.

I wouldn’t even doubt if it were due to eelskin wallets being primarily manufactured by companies who tended to use stronger magnets, or thinner linings. Or maybe the configuration placed the magnet closer to the strip than wallets made of other materials.

I bet it’s bias as much as anything else.