In an era that is increasingly threatened by the proliferation of nuclear weapons that come in all sizes, wonder weapons that can knock out continental power grids and even natural cosmic phenomena like solar storms.
Every single one of these events is capable of producing an EMP effect that can completely fry any electrical device that is not sufficiently protected or shielded from electromagnetic radiation.
The best defense against an EMP is what is called a Faraday cage, little more than an all-encompassing conductor that will deflect or harmlessly absorb the devastating burst of radiation before it reaches sensitive electrical components protected within.
A popular claim says that you can use common aluminum foil as a Faraday cage. Is that really possible?
Yes, it is possible to use common aluminum foil as a Faraday cage so long as it has no holes in it, has an insulating layer between its surface and the item to be protected.
Aluminum foil can create a Faraday cage effect when used as a pouch or as the liner or skin of another container.
As you might be thinking already, this is not an operation you can afford to get wrong, and even the smallest error can result in fried electronics that you would otherwise be counting on in the aftermath of a natural or man-made EMP event.
You would be wise to read up on all the factors involved in protecting sensitive electronics from these risks, and as a bonus, it can also keep your devices safe from hostile signals or signal detection technology.
What Exactly Are We Dealing With?
EMP, or electromagnetic pulse, is nothing more than a transient burst of electromagnetic energy, and in the context of survival it is thought of as a particularly high-powered burst, capable of damaging, destroying, or merely disrupting electrical equipment. As a rule, they are short-duration and affect multiple frequencies.
We are particularly concerned with the power and the frequency of an EMP insofar as that will dictate what level of protection is required to keep our electronics safe. Consider the EMP generator that almost every American home has in its kitchen: the microwave oven!
Have you ever noticed as you peer through the door at your slowly heating leftovers that the window has a fine metal screen set in it, a screen that has many tiny circular holes in it?
That mesh is, in effect, part of a Faraday cage that prevents the radiation emitted by the microwave from escaping through the glass window and microwaving your eyeballs.
You are witnessing the Faraday protective principle in action watching the microwave’s turntable go around and around. So long as the wavelength of the EMP is longer than the holes in the screen, they cannot escape. But…
Obviously, we must be prepared for the worst possible situation when dealing with a cosmically-generated or man-caused EMP, and will not rely on a screen unless we have no other choice. We want a solid shield of protection, and that is why we rely on foil instead of mesh whenever possible.
Constructing Your Aluminum Foil Faraday Cage
Constructing your own aluminum foil Faraday cage to protect your sensitive electronics from an EMP is fairly straightforward but you must pay close attention to detail.
Remember the following tips and guidelines as you read the instructions below. Getting any of this wrong could result in a false sense of security owing to an absence of protection for your electronics.
- Always use the thickest aluminum foil you can find. If you cannot find heavy-duty aluminum foil, that is okay, but you might need to construct additional layers in your Faraday cage for maximum protection.
- Aluminum foil is electrically conductive. That means the items you are protecting cannot be in direct contact with the aluminum foil layers, or else they will be fried when the EMP hits it.
- Always place a thick layer of plastic between the object you are protecting and the next layer of aluminum foil. You will repeat this between layers to prevent the skin effect whereby the EM energy will conduct for the outermost part of your Faraday cage toward the object you are protecting.
- You must take all precautions that neither your aluminum foil nor the insulating plastic layers have any holes, no rips or tears in them, or else protection might be reduced or lost.
There are two basic ways to construct a Faraday cage for your electronics using aluminum foil. The first is to create a series of pouches that completely close upon themselves with a layer of thick plastic sheeting between the object you’re protecting and its aluminum outer skin.
A single layer of plastic followed by a single layer of heavy-duty aluminum foil might be adequate to protect your electronics, but since this is an improvised method we can get even better protection by repeating that process, forming multiple layers of aluminum foil and insulating plastic.
This works pretty much like you are expecting: Simply wrap the object in plastic sheeting before wrapping it in aluminum foil and then add another layer of plastic sheeting followed by another layer of foil.
Repeat this procedure until you have three distinct layers using heavy-duty foil or four layers if you are using standard foil. You might also create several distinct, separate “pouches” that you can nest inside one another.
An alternate method is to create a series of rigid containers lined with an outer skin of aluminum foil. Standard cardboard boxes work fine for this, and cardboard also makes a decent insulator in place of plastic.
Ideally, you will nest the completed Faraday containers inside each other, one after another, like those Russian nesting dolls to obtain maximum protection. It is a good idea to wrap the object you are protecting and plastic sheeting as normal inside the smallest, innermost container.
Remember! It is imperative that you take your time, go slowly, and prevent damage to the aluminum foil and any insulating material while ensuring all bonds and connections are seamless and tight.
An EMP event can range in power from threatening to absolutely devastating, and you have to pay attention to details if you want to keep your stuff from getting fried.
Take your time, go slow, and create your Faraday cage with the precision and diligence of a watchmaker and your stuff should survive.
EMP Blocking and Signal Blocking
It is also worth mentioning that Faraday cages are naturally ideal for blocking outgoing and incoming signals from any device capable of transmitting or receiving them.
If you are worried about your phone spying on you, being tracked by hostile signals, or having your signals intercepted you need not hesitate: you can simply drop your device- radio, cell phone, controller, or something else- into your Faraday cage pouch or container and rest easy knowing that it is completely blacked out from the outside world.
While there is no easy way to test protection level against a real, live EMP it is a simple thing to test the signal-blocking capability of your DIY Faraday cage by placing your device inside and then testing it to see if it can receive signals in the form of a call or transmission, or even send its own signals.
For instance, if you try to call a cell phone that is powered up and residing inside a Faraday cage you should not be able to get a call through at all. If you can, you need to go back and check your work as you have probably made a mistake.
So… Can You Use It?
Aluminum foil used with care can, in fact, form an adequate Faraday cage for the protecting of your sensitive electronics of all kinds against the damaging or destroying effects of an EMP.
An EMP of catastrophic intensity is not just science fiction, so if you want your vital electronics to survive such an event, you must take steps now to protect them.
Tom Marlowe practically grew up with a gun in his hand, and has held all kinds of jobs in the gun industry: range safety, sales, instruction and consulting, Tom has the experience to help civilian shooters figure out what will work best for them.
5 thoughts on “Can You Use Aluminum Foil as a Faraday Cage?”
Great information, thanks. I’m going to use this to protect my laptops, cellphones, USB sticks, and a couple of backup drives. More budget priced than a metal briefcase or two, and especially helpful with me living in a studio apartment.
Thank You for this article, it is very informative. In fact I’ve constructed an improvised Faraday cage by using doubled kitchen aluminium foil and a small cupboard. I made two layers with this foil and isolation was made of white plastic trash bags (white with the aim to mitigate transmission of heat from outside between the layers). And in fact I’ve managed to test it and it passed the test perfectly. This test was very simple. I put one of my cell phones inside my F-cage and called it from another. And of course I couldn’t reach the number of the phone which was inside the cage. In fact it is a good method to test any cage if it is constructed properly and has no gaps through which the radiation can enter a cage. Hope it will help someone. Best regards.
You definitely have a point, I thought the same thing. If it takes a month or a year for the repair of the electrical grid then I guess you’ll be ready.
Does it matter which side of foil inside or outside?/shiny versus dull?
Also, if you use a closable box should I insulate with plastic and layers of foil where it closes and tie with string to make sure stays closed?
No, it does not matter. Keep in mind that the best plastic to use is three separate layers of 25mm visqueen.