Fun & Entertainment

Engineering the Ideal Tinfoil Hat: Material Selection and EM Shielding

How to Make a Tin Foil Hat

Suppose, hypothetically, you were a conspiracy theorist who believed in the Illuminati, malevolent aliens, lizard people, or some other shadowy group that controls the world.

Whatever it is, let’s call it The Huge Evil Megaconspiracy (THEM). It’s time to build a tinfoil hat to protect your brain from THEM!

The tinfoil hat would help to:

  • Prevent THEM from reading signals coming out of your brain
  • Stop THEM from sending electromagnetic radiation into your brain
  • Block mind-control beams
  • Make a bold fashion statement
  • Offer protection from EM radiation in excess of safe levels (There are real cases where one might actually want some shielding)

But is tin really the best material to make our hat out of?  What if we only have aluminium foil in the kitchen? What would be the best material we could use? Let’s put together our master plan to design the ultimate “tinfoil” hat!

Step 1: Consider common electromagnetic shielding materials

Let’s presume that in order to thwart THEM, we need a way to block electromagnetic radiation (EM) like radio waves. We will be focusing on stopping radio frequency (100 kHz to 300 GHz) EM radiation used by modern electronic devices.

These frequencies of EM radiation are generally considered to be harmless, so long as they are not too intense, but remain an area of active study and regulation.

tinfoil hat typical design
A typical design of a tinfoil hat.

We are essentially trying to create electromagnetic shielding for our heads, so we could look at materials already used in EM shielding as described in this article.

Attendee of the “Storm Area 51” raid wears at tinfoil hat as he and other Alien hunters gathered to "storm" Area 51 at an entrance near Rachel, Nevada on September 20, 2019. - Alien-hunters are arriving near Area 51 after a viral craze that saw them commit to storm the mysterious US military base as a variety of events are taking place to mark the weekend, including music festivals in a variety of locations. (Photo by Bridget BENNETT / AFP) (Photo credit should read BRIDGET BENNETT/AFP/Getty Images)

If you’ve already made your hat out of kitchen foil, then this is excellent news! The materials used in old-fashioned and modern kitchen foils, aluminium and tin, are already materials that work well for EM shielding.

But why is that the case? What if a global conspiracy only wants us to think these are good shielding materials? Let’s approach this problem from scratch and use Matmatch’s material property search engine to design the ultimate tinfoil hat. First, we need to figure out what properties make a good EM shield.

Step 2: Try our own material selection process

So aluminium and certain other metals are good for blocking various forms of EM radiation. But how does EM shielding work, and why are those materials good choices? The interactions between EM radiation can be complex, but the effectiveness of shielding tends to increase with the electrical conductivity of the shield.

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Faraday shields and Faraday cages block EM waves using an electrically conductive thin sheet that responds to approaching EM waves. When an electromagnetic wave approaches a conductive material, it induces charge carriers (electrons) within the material to move. The induced current creates a magnetic field opposite that of the incoming EM wave.

The shielding material can reduce the strength of EM radiation both by reflecting and absorbing it as it passes through the material. The ability of a material to either reflect or absorb EM waves increases with the material’s electrical conductivity.

faraday cage
A Faraday cage is a container made of conducting material, such as wire mesh or metal plates, that shields what it encloses from external electric fields.

If we perform a Matmatch search and filter by electrical conductivity, we can narrow down the most electrically conductive materials that would be good candidates for EM shielding.

MaterialElectrical Conductivity at 20 °C
(source in link)
Gold4.30 x 107 S/m
Silver6.00 x 107 S/m
Copper (oxygen-free)5.80 x 107 S/m
Aluminium3.50 x 107 S/m

From this table, we can see that silver and oxygen-free copper would likely provide the best materials for our EM-shielding hat. Gold and aluminium are also good choices. So it makes sense that aluminium would make an excellent shield, but we would upgrade to a hat made from copper foil or silver foil (if we could afford it) for improved performance.

Plus, if we picked a precious metal to make our tinfoil hat, maybe we could trick THEM into thinking we just have a very expensive and bizarre taste in fashion.

Step 3: Make it thick enough to block low frequencies

Even with a good choice of shielding material, we need to make sure our protective headgear is thick enough to stop incoming EM waves. In general, lower-frequency waves (closer to 100 kHz than 300 GHz), require a thicker shield due to their longer wavelengths.

A 25 µm thick copper foil (about the same thickness as heavy-duty kitchen foil) will absorb 99% (20 dB) or more of EM radiation above 50 MHz frequency. However, that same sheet will only block 90% of radiation at 10 MHz, and much less at lower frequencies.

In order to block lower-frequency radiation, a thicker foil hat is needed. Blocking 90% of EM radiation at 100 kHz would require 250 µm thick sheets of copper, or at least 10 layers of the 25 µm foil. So if we just want to block EM waves 100 kHz or more, we have a solution. That will show THEM!

Step 4: Add magnetic shielding to block even lower frequencies

So far, we’ve explained why copper would make an effective shield against most radio-frequency EM radiation between 100 kHz and 300 GHz. But what if our imaginary evil organization, THEM, is using lower-frequency radiation or magnetic fields to control our minds? (Plus why would they be making us design this hat?) We need a material with high magnetic permeability to block low-frequency EM radiation and magnetic fields.

If we perform a Matmatch search for metals with high magnetic permeability, we get an interesting result: a collection of nickel-iron alloys like this EFI Alloy 79. As desired, these nickel-iron alloys, sometimes called “mu-metals,” have a very high relative magnetic permeability (230000), but they also have modest electrical conductivities (1.70 x 106 S/m, calculated from the resistivity). Perfect.

Step 5: Success!

Now we can see how our ideal tinfoil hat would not be tinfoil at all. Rather, we could combine layers of oxygen-free copper foil with sheets of high magnetic permeability nickel-iron to create an EM-shielding helmet to protect us from THEM and their mind-control / mind-reading beams.

tin foil hat design
Here's is an illustration of how tin foil hat design might change if we use better materials like oxygen-free copper foil and sheets of high magnetic permeability nickel-iron.

The only challenge remaining is to figure out why they didn’t use the ray to stop us from designing our awesome super-helmet in the first place. It must be part of a larger conspiracy! 🤔

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3 Comments Add New Comment

  1. Most high frequency shielding problems are caused by openings in the shield material, and not by the material itself. Most conductive materials such as aluminum, copper and mild steel provide substantial electric shielding. At frequencies from 30 to 100 MHz, aluminum foil provides at least 85 dB of shielding effectiveness. Unfortunately, aluminum foil is extremely inadequate against low frequency magnetic fields, where thick steel or highly permeable ferrite material provides more adequate shielding. These conditions are just some of the many reasons that shielding has limited effectiveness, creating the requirement for added filtering.

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