Will mylar block RFID signals?

I have an idea for a small leather work project that would utilize mylar film as an RFID signal blocker.  I have tried to research the effectiveness of mylar film for this purpose and the consensus opinion seems to be a resounding "Yes, No and Maybe."
If anyone can point me to an authoritative source or has personal information relating to this, I would be most appreciative.

Thanks

Addendum:
Much as I anticipated, you have posted a host of excellent answers that gave me a lot of information I hadn't yet considered.
For my part, I should have included more information concerning my project in my question.
The Skinnerz response reminded me that I have some scraps of fine mesh stainless steel screen termite shield and I will give that a try rather than mylar for my wallet and passport case.



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Radio waves can normally be blocked by surrounding the detector with an earthed metal sheet or mesh, so you could try replacing the mylar with piece of metal sheet, possibly connected to ground.
orksecurity6 years ago
Depends on the frequency, depends on the signal strength. As others have said, this HAS been considered when designing anti-shoplifting systems.
May depend on the protocol too, come to think of it.
... and, yes, that's assuming you're talking about metalized mylar with a thick enough layer of metal.
Straight Mylar is not metallic, so I would say that it alone would have no effect on the ability to read the tag.

A lot of the mylar films have a metalized film on them, like baloons. These may have some chance of blocking detection, if the shield is made such that it sufficiently surrounds the tag. One problem here may be that if the metal on the film is much thinner than a skin depth at the frequency of operation of the tag, then the shielding effect would be reduced.

My advice would be to get some low cost reader and tags that are representative of those in common use, and experimentally determine how successful it is.

Yes that's right about Mylar.

L
kevinhannan6 years ago
I'm sorry I don't have an authoritative view.
You can always contact a mylar company/factory and see what they say.

fwiw - I don't think it does. My experience with mylar is as a light-reflector which I used to make years ago.

but I'm wondering why you are thinking of mylar within a leather project. Can another, flexible sheet of something be a better bet, such as aluminium foil, or one of those space-blankets easily bought in any pound-store. In any case, mylar is cheap, is there an opportunity for you to test it yourself? I also seem to remember there are benefits in doing multiple layers.

Frankly I'm surprised this has not been done before now for professional shoplifters, where a lady can have a rfid-proof bag and walk through security - or a poacher's jacket with lots of inside pockets - but I'm not suggesting for one minute this is your project.

It's also useful to protect your contactless, cashless card in your wallet from opportunistic thieves who might walk by with a portable scanner. It sounds like a fantastic project.

If I were you, if there is no authorative answer, go to the source and ask the manufacturer direct. Failing that, perhaps a university doing work in security products (yes, they really do tings like that!)

Good luck. ;-)
seandogue6 years ago
I can't answer authoritatively, but I don't think so. I've seen enough rfid anti-theft tags that were inside wrapped packages that I suspect it doesn't, or at least not unless it's aluminized mylar