How to Make a Faraday Cage in 4 Easy Steps (and What to Put In It)

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By the author of Be Ready for Anything and the online course Bloom Where You’re Planted

If you’ve been in the prepper world for long, you’ve probably read some horrifying books about what can happen after a disaster called an EMP.  And if you’ve done that, you know you need to protect vulnerable electronics. Today, we’ll talk about how to make a Faraday cage to do just that. Don’t worry – you won’t need a degree in physics to do this successfully.

First, let’s start off with a few important things to know.

What is an EMP?


“EMP” is short for electromagnetic pulse. It is a short burst of electromagnetic radiation that could come if a nuclear detonation occurred at very high altitude above us.

When a nuclear explosion occurs in space above a target, three types of electromagnetic pulses follow: E1, E2, and E3. An E1 pulse involves high-energy gamma rays colliding with air molecules nearly 20 miles above, then raining down electrons that get pulled in by Earth’s natural magnetic field. An E2 pulse comes from high-energy neutrons that get fired in every direction, and an E3 pulse occurs due to the size of the nuclear fireball itself affecting the Earth’s magnetic field. As nuclear physicist Dr. Yousaf Butt explains, these pulses affect everything in line of sight of the nuclear blast. For example, a blast at 60 miles up can affect a 700-mile radius on Earth. (source)

And by “affect everything” they mean everything with a circuit board. Your car. Your laptop. Your computerized medical devices. The power grid in general.  All of it.

This probably sounds like a sci-fi disaster movie – and it is like that. But it could happen. The Commission to Assess the Threat to the United States from Electromagnetic Pulse (EMP) Attack has warned Congress of the devastation that could follow such an event.  But for some reason, Congress defunded them last year.

At a House hearing yesterday, experts warned members of Congress that a North Korean EMP attack could kill 90% of Americans within one year, calling it an “existential threat.” But despite this looming crisis, the Department of Defense has decided now was the time to defund the Congressional committee that has been studying the threat since 2001. (source)

We’re talking about the deaths of more than 270 million people. Even mainstream sources have posted articles warning about this concern, particularly last fall when we were on edge about North Korea.

They have things set up where the military can continue to function, but it appears that the rest of us are on our own.

President Trump signed an Executive Order in May called “Strengthening the Cybersecurity of Federal Networks and Critical Infrastructure” which will hopefully harden our country against both cyber attacks and EMPs. The Commission provided a list of actionable suggestions on pages 11-14 of this report, but will the steps be undertaken before it’s too late? Especially now that they’re defunct.

It’s important to note that, although there are some differences, a very similar event could occur in the wake of a coronal mass ejection by the sun. Either of these possibilities could fry electronics in the affected area and completely change the world as we know it.  There are debates about exactly what would be affected – for example, some scientists say that only vehicles that are running would be affected, while others say if it has a circuit board, it’s history.

But for the purpose of this article, we’re going to assume that all of our electronics face total destruction.  Better safe than sorry, right? And that’s why you need a Faraday cage.

What is a Faraday cage?


A Faraday cage is a container that is made to protect its contents from an EMP or CME. It’s named after the original creator, Michael Faraday, an English physicist and chemist who lived from 1791-1857.

In his work on static electricity, Faraday demonstrated that the charge only resided on the exterior of a charged conductor, and exterior charge had no influence on anything enclosed within a conductor. This is because the exterior charges redistribute such that the interior fields due to them cancel (the Faraday cage principle).

To demonstrate his ideas, Faraday built in 1836 a room (the Faraday cage), coated with metal foil, and allowed high-voltage discharges from an electrostatic generator to strike the outside of the room. He used an electroscope to show that there was no excess electric charge on the inside of the room’s walls and volume.

The Faraday cage can be used to prevent the passage of electromagnetic waves and electric fields, either containing them in or excluding them from its interior space…

…Take notice that Faraday cages also shield the interior from external electromagnetic radiation, besides from electrical fields, if the conductor or wall is thick enough and any holes are significantly smaller than the radiation’s wavelength.

This shielding effect is used to protect electronic equipment from lightning strikes and other electrostatic discharges, for RF (radio frequency) shielding and for shielded telecommunication cables. (source)

So, more simply, a Faraday cage is a container in which you would house your most important electronics that would have some function in a world after our power grid was taken down. In a moment, we’ll talk about how to make them and test them.

Here’s an introduction to EMPs and Faraday cages by Dr. Arthur T. Bradley. Dr. Bradley is a scientist for NASA, the prolific author of The Survivalist series, and the author of Disaster Preparedness for EMP Attacks and Solar Storms, so he definitely knows that of which he speaks.

What should you put in a Faraday cage?


The answer to this will vary from family to family. Here are a few items to consider

  • Electronic medical devices such as CPAP machines
  • Communications devices such as two-way or ham radios
  • An NOAA radio
  • A laptop or Kindle device with important information on it (PDFs, books, etc.)
  • Solar battery chargers
  • LED flashlights (incandescent flashlights don’t require protection)
  • Computer hard drives

Again, this list is not comprehensive – it’s just a few thoughts off the top of my head. My own Faraday cage won’t contain much more than the list above because my EMP survival plan is decidedly low-tech. If you’ve been following Anon 411’s information series, protecting that information is a must.

Where can you get a Faraday Cage?


There are a number of different ways to obtain something in which you can protect your electronics. You can buy them, which is the easiest way, but significantly more expensive. Keep in mind it’s always best to double up. For example, but your laptop in an EMP resistant bag and house that bag in your cage.

Here are a few of the things you can buy:

Then there are the EMP-resistant bags and cloths.

But…if you don’t want to spend this much money, you can also make a faraday cage yourself.

Make a Faraday Cage in 4 Easy Steps


Very simply, you can make a Faraday cage using a metal container, then lining it with an insulating material so that the items inside do not have contact with the metal. It’s all about layers. I prefer to have 3 layers of protection.

Step 1) Select a container for your Faraday cage. Some ideas for the containers for the outer layer:

  • A galvanized metal garbage can
  • A popcorn tin
  • An ammo can
  • A metal filing cabinet
  • A wooden box wrapped in numerous layers of heavy aluminum foil

Here’s why you should NOT build your Faraday cage out of chicken wire.

Step 2) Line your container. Here are some ideas for the second layer:

  • Thick fabric
  • Cardboard
  • Styrofoam

The goal here is that nothing on the inside touches the metal of the container.

Step 3) Wrap up the contents before you put them in the cage. You will want to protect each item individually.

Step 4) Seal your container. Copper tape like this is widely believed to be the best method for sealing a Faraday cage to protect the contents. Dr. Bradley says that when testing Faraday cages his results have been just as good with less expensive aluminum foil tape.

  • If you’re using a trash can, ammo can, or popcorn tin, put several layers of tape on the lip of the can. Put on the lid – it should fit very snugly. Then, go around the outside where the lid meets the can and put a few more layers of tape.
  • If you’re using a filing cabinet, put several layers of tape around the edges of each drawer-front. Then, close them snugly and run more aluminum tape around each seam of the cabinet.

Testing…1…2…3


Here’s a video that explains how to test your Faraday cage to see if you need to go back to the drawing board.

Want to learn more?


Here are some excellent resources where you can learn more about protecting electronics from an EMP.

Do you have a Faraday cage?

Here are some questions for discussion. Do you have a Faraday cage? What did you make it from? What do you keep in it? What are some important things about the necessity of a Faraday cage that you want to share with people?  Feel free to ask questions, too. If I can’t answer them, I can try and find the answer for you.

 

Daisy Luther

Daisy Luther

Daisy Luther is a coffee-swigging, globe-trotting blogger. She is the founder and publisher of three websites.  1) The Organic Prepper, which is about current events, preparedness, self-reliance, and the pursuit of liberty on her website, 2)  The Frugalite, a website with thrifty tips and solutions to help people get a handle on their personal finances without feeling deprived, and 3) PreppersDailyNews.com, an aggregate site where you can find links to all the most important news for those who wish to be prepared. She is widely republished across alternative media and  Daisy is the best-selling author of 5 traditionally published books and runs a small digital publishing company with PDF guides, printables, and courses. You can find her on FacebookPinterest, Gab, MeWe, Parler, Instagram, and Twitter.

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  • The filing cabinets that I have had all were open at the bottom. Probably to save cost and weight. So you will need to fill that in with something metal. They all also had a small hole (1/8 inch or so) near the bottom on the back. Not sure what that is for, but you will want to put metal tape over that and any other holes. If your filing cabinet has a lock, you should put metal tape over that too.

  • I’m surprised nobody has designed a “faraday house” – wrap the entire thing in copper mesh.

    I’m sure the 1% have them…

  • Yes, I have two Faraday cages, both made from mid-sized galvanized trash cans. They are lined with corrugated cardboard on the bottom and side of the can. Nothing will be touching the lid.

    In one can I have eight two-way radios (mine are not CB, but FRS, MRS and Ham bands) so that if the SHTF I can give my neighbors some way to communicate with me. I also have an old laptop, a small solar charger, night vision goggles and an IR rifle scope.

    In the other can I have my drone, my ham radio and some test equipment.

    Radios are recharged when we change the clocks, and only two at a time are outside the cage.

    I also have 200W of solar panels and charge controllers so I can use car batteries and keep a supply of electricity to run the laptop and any other stuff that needs electricity. These are wrapped in HD foil and protective cardboard and stored in the barn. I have read that solar panels do not need protection, but since they are not in use, protection is just a one time thing.

    It took years to get all this together, so don’t think that it can happen overnight. Plan now and work towards your goal.

    Ray

  • If you use an ammo can, remember that they have a rubber seal around the lid.
    Make sure you tape that area well with metal tape.

  • Does a resealable mylar bag that blocks a cell phone signal qualify as a Faraday device?
    I travel with my cell phone in a dog food bag that shields the phone from receiving a signal. Works well until more than one device goes in. Add a Kindle and small tablet and the phone rings right away.

  • Will a Microwave Oven work as a faraday cage as is? They keep energy in so will they keep energy out?
    Can a faraday cage be tested by something like putting a cell phone in and calling it?
    Thanks

    • I advise you watch the video at the end of the article about testing. There are all sorts of theories out there about testing your Faraday cage, but Dr. Bradley’s is the advice I would take.

  • I have a few trash can faraday cages. One is filled with my Civil Defense meters, dosimeters and chargers, plus one lantern and a radio. This is taped shut and stored in my designated shelter space, since if we get hit with an EMP then in a couple of days I’m really going to want to know if any of the nuclear power plants upwind of me have started venting….
    The other cans are filled with a mix of radios, flashlights, lanterns and solar chargers. That way if one can is open when the ball goes up, I still have the other gear to fall back on before I have to go with non-electric options. And post EMP, I only plan on removing one flashlight and one radio for the first few days, just in case we get hit with multiple EMP attacks spread out over a few days (good military tactic is to hit with one EMP, wait a day for folks to take backup gear out and get it installed, then hit them again with another EMP to fry the backups.)
    I bought my galvanized trash cans locally and made sure there was no rust, no dents and that the lids fit tightly. Once I filled them and taped them up I put them up on boards or on other floor coverings so they aren’t sitting directly on concrete. Don’t want to test how rust resistant the cans really are, since rust would impact the electrical conductivity and could make them less effective at protection.
    And while I have plenty of non-electric options for light, electric lights are much more space economical as long as you have rechargeable batteries and a solar charger option. With my Enerloop batteries, a solar charger and a lantern I will have light at night for years (assuming I charge alternating sets of batteries daily, 2100 charge cycles will last over 11 years…)
    Thanks for a timely article as tensions with Iran ramp up and we’re at a perilous crossroad with North Korea. Hope for the best, but prepare for the worst.

    • I bought a bunch of those $2 solar walkway lights at Walmart, and left the paper pull-out in place so it won’t function yet. When “the lights go out and don’t come back on”, you can pull the paper and place them outdoors and they recharge and use them at night indoors for light ! Some of the models last all night long for light ! Anyway, a cheap and very usable light source for when the grid goes down longer term. By slightly modifying them a switch might be able to be inserted in some way so as to turn them off at night and save the remaining charge, but I haven’t done that yet.

  • I appreciate the attempt to help people prepare for all kinds of disasters, but I’m going to have to throw a conversational bomb into this room, so to speak.

    EMP is a total scam. See here: https://www.lewrockwell.com/2018/02/david-hathaway/emp-hoax/

    Not only is EMP a scam, nuclear weapons are probably a scam. Certainly they were at the time of abhorrent and immoral destruction of Hiroshima and Nagasaki, both cities victimized by fire bombing like all the other Japanese cities.

    I suppose protection against lightning might be useful, a system of lightning rods being an alternative. I wouldn’t lose sleep at night over this EMP nonsense, especially when there are real dangers we face every day.

    • Do you prepare for blizzards and hurricanes? They don’t happen every day, yet they are a real threat to life and limb.
      How about preparing for the electrical grid to go offline for days? or weeks? or longer? The reason doesn’t matter much to folks impacted by it. Seriously, does it matter if hackers take the grid down, or if terrorists attack the interconnects and substations, or if a solar flare fries the transformers? The only difference to you and me is how long it will take TPTB to get things going again.
      If you don’t prepare for low probability but high impact events then I’d say you aren’t serious about protecting yourself and your family.
      I happen to think that buying a few galvanized metal trash cans and a couple of rolls of aluminum tape was short money in case we are hit by an EMP. If we never get hit (whether that’s because they are a hoax, or because nobody wanted to see if our military would hit back), then I’m out about $100. But if it’s not a hoax and we get hit, I’ll be glad to have some small electric lights available to me and my family.

  • My faraday cage is a metal garbage can lined in a yoga mat cut to dimensions inside the can and lid. Is this enough insulation ?

    • The question is whether or not your Yoga mat is conductive. If it is, you don’t have a cage. That’s why the trash can is lined with corrugated cardboard; a known insulator.

  • I am curious, if an emp is possible and a real threat, what is the purpose of having and protecting a spare lap top? If the grid is down, what makes anyone think the internet would be up and running? And even if you could re-charge it using solar power, what are you going to do with it? You can’t use it to communicate, you can’t look things up on the internet, you could MAYBE use it to file your recipes and “End of the World” info, but only if you have saved all that stuff ONTO the computer. Personally, I have all the info I need on paper, in books, copies of important documents in my emergency binder, etc. I don’t like computers in the first place. I have one laptop, my husband has one, we don’t need a spare. I have better places to spend my money and better things to protect. Only thing I can see it being useful for in a grid down situation is a paperweight and to hold my place open in the cookbook. Likewise, if you have electric medical equipment, you should have an alternate way to charge and / or run it without electricity. As mentioned in the follow-up article, “EMP: Hoax or threat,” there are multiple scenarios that could bring the grid down. So if you are dependent on an electric machine of some kind, give serious thought as to alternative ways to power it.

    • If it’s not for you, it’s not for you. Ideally things should be in hard copy. Unfortunately, I have lost 3 decades of books and the easiest way to replace them in a timely manner was by electronic fashion. I have bought as many used books as budget allows, but it is nothing now to have hundreds of thousands of books on a single 2.5″ drive. Obviously it’s not for trying to use the internet in a disaster. There are many other additional uses like measurement, wired security and data logging.

  • I highly doubt we need to fear EMPs. The U.S. government will do everything it can to keep its electronic surveillance grid working.

    In terms of general protection from RF energy and radiation, it would be nice to be able to not just have a nice little box to keep cell phones from spying on us but something we can live in to keep safe from 5G radiation. How about a method of shielding and grounding for an entire home?

    • I’ve always questioned whether or not aluminum would work as a shield. All my cages are ferrous (galvanized trash cans or ammo boxes) or copper screened.

      Did you line your case with cardboard?? Whatever you are trying to protect should not be in electrical contact with the shield.

  • Does anyone know a bookie who’d cover a bet on when and if an EMP event will happen? The odds of it happening are possibly 1,000,000,000,— 1 or higher. If an EMP weapon is so powerful; WHY HASN’T ANYONE USED ONE YET?

    • From what I’ve read, it’s been done twice. The first was the US with Starfish Prime (totally unplanned for) that was reported to have affected power and lights 800 miles away in HI, and the second was the Russians who popped one over Khazahkstan (no doubt spelled wrong, and it may be a different satellite in the USSR). The discovery of the EMP effects of a nuclear explosion in space was a major impetus for one of the nuclear treaties that we signed with the USSR, from what I’ve read.

      Back then, almost all electronics were vacuum tubes, a very robust system. Now we have microprocessors that can be zapped with 100V of static electricity. Would not take much induced surge to fry our modern tech. That spark you generate walking across the carpet is about 50,000V.

      There are a couple of things to keep in mind:

      1. EMP is only effective against a society with high tech. It would be totally ineffective on all 3rd world countries and only marginally effective on many 1st world countries (some have hardened their power distribution systems, unlike us.)

      2. The countries with the capability to use an EMP are also the same ones who would suffer from it being used on them. We’re the highest tech country in the world, at the moment, and that makes us a target if someone can hit us anonymously.

      3. The nuclear retaliation against anyone who hits a nuclear power with an EMP and doesn’t do it completely anonymously will result in that country being incinerated. MAD works for the most part, which is why, I think, there is so much effort made to keep Iran from getting a nuke. They’re detonating test missiles at apogee and calling the test a success. Smaller groups (non-country things like ISIS) can’t get the platform, infrastructure, money or weaponry to launch a nuclear tipped missile and have it detonate over St. Louis. Not yet, anyhow.

      4. I read a report that back when the USSR collapsed and some of their ‘secrets’ were being divulged, one of the generals with knowledge of their nuclear war plans said that any attack against the US would be initiate with a nuclear weapon detonation in space, generating an EMP as the first strike. I’ve no reason to doubt the logic; whether or not it’s true is another matter.

      5. While the risk is small, so is the risk of a tornado hitting my 100 acres on the edge of Tornado Alley, but I’ve got a safe place in the basement that is always ready. A galvanized trash can with a cardboard liner isn’t expensive and worth the small price if ‘what-if’ happens. If you own a home, you have home owner’s insurance, not because you expect your home to burn to the ground, but for ‘what if’. All that said, you have to weigh the risk versus the cost. There are EMP blankets that you can buy to protect your car, but they are, IMO, not worth the cost. However, EMP Shield makes a $300 device that mounts to your car that is fast enough to bleed off any EMP generated voltage/current spike to protect the car. Cheap enough to qualify as insurance.

  • Years ago a good friend of mine was attending an engineering school. For one of his projects he decided to make various EMF-blocking units. He spent a fortune on various materials and made bags, boxes and tubes. All of them performed admirably. After everything was tested and graded (he aced that one), he handed out most of the bags he had made to his friends. The one I got is large enough to hold my Baofeng radio and charger, two walkie talkies with charger, external hard drive (mechanical), a handful of flashdrives, an ancient Gameboy with a dozen games, spare batteries and a small tablet. I could probably squeeze in my Aimpoint PRO also, and maybe I should. Everything is individually plastic bagged to protect against moisture (I live almost right on the ocean, very humid all the time). All of this is placed in a hermetically sealed bin (plastic), which is then wrapped in two layers of Mylar blanket and placed in another tote for easy grab-and-go. I’m pretty confident that all my vital electronics and data are well protected.

  • The reason I believe that the US has not done more about dealing with EMP (well, one of the reasons), is too non-PC to post here now, with the problems Daisy is having with de-funding, etc.

    However, for whatever the reasons are, it is not being done, and therefore is up to the individual and like-minded groups to take care of the risk themselves. I have made several Faraday boxes for myself and several other people, have a couple of Mobile Sec Solutions https://www.mobilesecsolutions.com/products bags for items that require great protection and easy access.

    I have researched and developed plans to protect solar PV panel installations; powerhouses for gensets, battery banks, associated electrical and electronic devices; shelter/shelter rooms; communications consoles; EmComm boxes; and vehicular Faraday boxes for mobile equipment; as well as areas such as pole barns, unattached garages, and the biggie, whole houses, if done during initial construction. (Retro-fitting a building is nearly impossible, though during new construction, and perhaps remodeling for individual rooms, is fairly easy and not all that expensive.)

    One of the most difficult things to do for larger Faraday cages, and essentially anything that needs to be accessible with the ability to reseal against EMP quickly, easily, and thoroughly, but that is, actually, with products now available, fairly easy and not that expensive to do.

    Doing the due diligence research, and keeping an open mind, coupled with a bit of ‘out-of-the-box’ thinking, and all of it is doable. Some things cost more than others, and the costs are climbing quickly, and especially the availability of materials can be a problem. So, I suggest analyzing your needs now, deciding on what to protect and how, setting up a budget, and getting it done.

    Just my opinion.

  • I have read info and comments. Good Items, but I really want to know how to protect my 10KW Diesel Generator form EMP. No one seems to address this, or at least I missed it.
    I purchased a large roll of rather fine copper mesh on Amazon and wrapped the control panel which houses circuit control gizmos and generator start and stop switches, controls, etc. Then I purchased a nice alligator clip and single male plug each on an end of a long wire. This is made to be plugged into the ground of a standard electrical outlet in the house which in turn is grounded to the main ground rod which grounds all of your house electrical system. The idea is that I must send the EMP charge off of the control panel copper mesh and ground it. Otherwise, the charge may just sit on the cage. The solar EMP of the mid-1800’s was so strong that it physically burned down telegraph buildings when the long wires brought the energy into the buildings. I would like more specific info on how to properly protect my generator from EMP???

  • I built a couple of faraday boxes years ago using cardboard boxes from reams of paper. I taped the entire boxes with Foil Tape 3340. I completely sealed one. However, the second one had things that would need batteries changed or had circuits. For those, I wrapped the bottom and the top separately. when I slid the top on, it had a good tight fit with the bottom. Is that still considered to be sufficient? Thanks!

  • Faraday cages have to be grounded at a single point to be effective. Otherwise, they saturate with RF and damage the contents.

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