Using Aluminum Oxide Paint To Secure Wi-Fi

eldavojohn writes "The BBC reports on people using aluminum oxide in their paint to block Wi-Fi signals from leaving their home or business. Aluminum oxide resonates at the same frequency as Wi-Fi signals and other radio waves, blocking data from going outside a building. It's not a flawless solution, as it may also block AM/FM signals. You or your neighbors may be unwittingly using this already, as most pre-finished wood flooring uses aluminum oxide as a protective coating."

Comments

Cellphone reception?

[beef curtains]

Wouldn't keeping radio signals in also have the unfortunately side effect of keeping radio signals out? While having a neighborhood coffee shop offer free wifi to paying customers while being an of oasis of cellphone-free peace & quiet would be sweet, having no cellphone reception at home because one desperately wants to prevent neighbors from stealing one's wifi seems very inconvenient (especially when setting up even the most basic built-in wireless router security would successfully do the trick in 99.9% of cases).

Re:Cellphone reception?

[pz]

I stand corrected on the water resonance part.

The impedance part, well, perhaps Mr. Pink Corner needs to understand more where resistance comes from. The reason that microwave ovens work at all is that there is a resistive (ie dissipative, lossy, real, call it what you will) component to the impedance of water at those frequencies, dissipating EM energy into heat. Here's a quote from the nicely informative link Mr. Pink Corner provided:

Rather than interacting with the water molecules via a resonance, the microwaves in an oven heat the water by twisting its molecules rapidly back and forth so that they rub against one another. The molecules are heated by the molecular equivalent of sliding or dynamic friction. The choice of 2.45 gigahertz gives the water molecules about the right amount of time to twist in each direction. The precise frequency isn't important, but microwave ovens are required to operate at exactly 2.45 gigahertz so that they don't interfere with communication systems using nearby frequencies.

And here's another clue about physics, Mr. Pink Corner, when you have a complex impedance, like an RC circuit in a lumped model system, the speed of light through those components is determined by the RC time constant. The speed of light is slowed by the reactive portion of the impedance. In that system. Otherwise the movement of the current would not be impeded and the full voltage would appear at the far side of the C element instantaneously. But it does not: the speed of propagation is slowed, as reflected in the time constant. This becomes especially evident when you look at transmission lines and the impedance of the line determines the propagation speed (as well as the line loss due to heating of the real component of the impedance). Same thing in water, except, as I've been corrected, there is no resonance at 2.45 GHz.

Re:Extra protection?

[ColdWetDog]

May not be better but it could be more, how shall we say, stylish. Maybe quieter as well. I do like his pandering to the 'think of the children' racket.

"We're assuming that excessive exposure could be bad for us. Therefore we're trying to make protective clothes for young children or pregnant women to help protect their bodies from such waves."

Give me a break. Next think he'll be trying to create is an Aluminum oxide / silver dip - keep away nasty radio waves and germs, all in one toxic package.

I think this guy is mostly looking for some investors.

Why not share wi-fi?

[presidenteloco]

We do know the world would be a better place if everyone shared their wi-fi securely using
a technology like FON, don't we. (No I'm not associated with the company. Just recognize a
great concept when I see one.)

I'm seriously tired of how, particularly in the US, sharing wi-fi gets implanted in peoples'
brains as a criminal, borderline terrorist activity, with terms such as
"theft of tele-communication resources" and similar Orwellian mindf**k terms.

Re:Does not resonate with me

[_avs_007]

Seriously... I work with a WiFi lab at work... I have a Faraday Cage in our lab... One of the techs forgot to install an optical isolator on the network cables, so for a few days the ethernet cables went right into the cage... Well, first day I went to use it, I locked myself in the cage, and was surprised that my cellphone started ringing... Without the optical isolators on the network cable, the RF signals were able to find there way into the faraday cage through the ethernet cables....

with that being said, I highly doubt that simply painting your walls will keep RF signals at bay... Even when the grounding wire was simply loose on the door to the faraday cage, RF signals would leak in...