Eelskin Wallets

[CalMeacham]

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

(the column is here: Do eelskin wallets demagnetize bank teller cards? - The Straight Dope)

After a sudden rash of complaints about bad cards from eelskin-wallet owners, Katie and her colleagues examined the magnetic stripe on several failed cards and found that magnetic information had in fact been erased. They further noted that most of the complainers were women who used eelskin wallets with large magnetic clasps. As an experiment, Katie ran a variety of magnetic items over some test cards. Sometimes the cards became demagnetized, sometimes not. But when she ran an eelskin-wallet clasp over the cards, they always became demagnetized, even at a distance of two inches. A call to the fellow who owned the patent on the special donut-shaped magnet used on eelskin wallets confirmed that the magnet was unusually strong. (Why you need a heavy-duty magnet on an eelskin wallet is not clear to me, but hey, not my problem.)

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

[edit] Eelskin Wallet
Myth statement Status Notes
Using an electric eel-skin wallet will cause a static charge that will cause the magnetic strips on credit cards to fail. Busted Most eel-skin wallets are not made from electric eels, but rather from a fish called a hagfish which does not produce an electric charge. Data written to a set of test cards were not affected in any way.
In addition, further tests were conducted to see how much magnetism would it take to ‘wipe’ a card, and was found to be far above what the average person may encounter.

From the Wiki entry on this episode:

MythBusters (2003 season)

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?

[John_W.Kennedy]

@CalMeacham

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.

[CalMeacham]

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.

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.

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.

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.

[Half_Man_Half_Wit]

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).

[Half_Man_Half_Wit]

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.

[SeanArenas]

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.