Can You Use Aluminum Foil for a Faraday Cage?

We’re in an era that’s 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 (electromagnetic pulse) effect that can completely fry any electrical device that is not sufficiently protected or shielded from electromagnetic radiation.

DIY cardboard box and aluminum foil Faraday cage finished
DIY cardboard box and aluminum foil Faraday cage finished

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, and 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’re 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.

Building 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.

  1. Always use the thickest aluminum foil you can find. If you cannot find heavy-duty aluminum foil, that is okay, you might need to construct additional layers in your Faraday cage for maximum protection. To do this, you just wrap the aluminum foil 3-4 times.
  2. Aluminum foil is electrically conductive. That means the items you are protecting cannot be in direct contact with the foil layer, or else they will be fried when the EMP hits it. As such you should always place a thick layer of plastic between the object you’re protecting and the layer of aluminum foil.
  3. 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 aluminum foil, or several.

You might also create several distinct, separate “pouches” to better hold your items in place, and avoid any rattling should you take the box with you as you’re bugging out.

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.

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’s 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.

aluminum foil uses Pinterest image

14 thoughts on “Can You Use Aluminum Foil for a Faraday Cage?”

  1. 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.

    1. Protecting your cell phone and our computer won’t do you any good if all the towers in the United States are fried! Get yourself a solar generator and put it in a faraday case. You also have to put the solar panels that come with it in a faraday case I bought a small refrigerator and a small freezer and have protected them as well. They are still in the box brand new, because everything in your house will be fried, the smaller fridge and freezer drawer less power and therefore should be sustainable for a long period of time. Good luck.

  2. 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.

  3. 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.

  4. 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?

  5. Hi, I want to protect my portable generator from an EMP. It is too big to usealuminum foil. Can I use aluminum sheet metal that is a lot thicker than foil?

  6. Contrary to what the article says, the inside of the Faraday cage does not have to be insulated. The devices you are trying to protect inside the Faraday cage can literally be touching the inside of the cage with no harm to them.

    1. Dan F. Sullivan

      Given the metal Faraday cage will have electric current pass through it, any touchpoint between the metal carcass and the items inside will transfer current to those items… So why wouldn’t you want to have insulation?

  7. With respect to generators, there are designs on internet for simple faraday cages. A relative built me a cage from aluminum screen, 2x2s, and metal tape. The generator rolls over a screen that can be bent up and the cage fits over the generator. Lower screen will be bent up and sealed with tape. Small taped openings will be cut and taped to allow periodic starting of generator.

  8. My smaller items are to be protected by a 10 gallon steel, locking garbage can (Behrens) and a 6 gallon pail (Tubtrugs) fitted inside. All the openings (handles, bales, etc. are sealed with aluminum tape. I will test with a radio and a cell phone. The top of the garbage will be sealed with tape when I have checked and loaded. The design for this is available on the internet.

  9. I have a question, can one use “foil backed foam insulation” this would have some rigidity, two layers of foil with foam insulation between. This would have the advantage of being able to cut panels to size needed and should be able to use metallic metal tape to seal edges?

  10. I have a solar generator and panels in a faraday bag. I am using galvanized trash cans with bubble wrap inside to protect a small microwave in the box, 24 inch tv and dvd player in boxes they came in. I sealed around the handles and the lid with alum tape. I built a wood box with light alum facing for my small refrigerator still in the box. I triple wrapped and sealed joints with alum foil and metal tape sealer.

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