Two Letters Re: EMP Shielding for Electronics

Maybe I missed something during the acquisition of several undergrad degrees, including one in physics (actually, I probably missed several things)… but how exactly does a Faraday cage have any effect on uncharged particle emissions (neutrons) as suggested by the author of the article that you recently provided a link to? And since when did Einstein claim discovery of an element (Uranium) that
was discovered in the 1700’s?
His cages might work (hard to actually test anything vs. EMP without doing rather large scale experiments), but that sort of nonsense kinda damages his overall credibility. – Simple Country Doc
JWR Replies: The author did get a few facts wrong, as you pointed out. But his basic premise on shielding is sound. The Wikipedia piece on Faraday Cages provides further details.


Hi James,
I enjoyed looking at the link you provided about EMP. If there is ever a threat that will have a magnitude un-matched by any and all other terrorist activity combined, it would be a high altitude EMP attack, (in my opinion). Finding legitimate information and trustworthy sources is tough.
I like the simplicity of this featured “box in box” Faraday Cage, but wonder how well cardboard actually insulates at a conductivity level. In other words, I fear that the work would be for not if the cardboard became damp at any time which in this design is quite likely. Wrapping any object in Visqueen [sheet “painter’s plastic”] or some non-permeable substance, change the temperature of the environment that it is in, and whamo, condensation.
I have no background in designing or testing such ideas, but common sense prevails in this matter. To me damp cardboard becomes a conductor, and not an insulator. A wood box would render the same results. I wonder if there would be some merit to a box out of glass, or maybe even some Pyrex container with matching lid and Mylar tape or Foil tape the seam to the ground wire? How about a glass aquarium for the larger items? Go to your local auto glass or commercial window supplier and have them cut you exact tolerance lids for the larger items.
How about adding the dry-ice in accordance with your earlier posts for long term food storage to displace oxygen and add absorbers as well? Ultimately, I think a semi-controlled environment would be a good idea. This does not solve the condensation issue; it does however put the items inside of a non absorbing insulating medium. I understand other precautionary measures would be prudent, (i.e.- foil, chicken wire, copper mesh, etc.) just trying to expound upon an idea and hear what other’s with more knowledge can add to this discussion. Happy Holidays, – The Wanderer

JWR Replies: Glass would work as a damp-proof insulator, but it is fragile. I would instead recommend using a plastic box, such as Tupperware, for the inner box. The dry ice and oxygen absorber methods that you mentioned are only useful for killing pests. (They don’t necessarily drive out moisture.) Stopping condensation is best accomplished by A.) Enclosing some freshly dried silica gel, gypsum, or a similar desiccant, and B.) Using an outer container that has an airtight seal. Desiccants can be “freshened” (i.e. have any collected moisture driven out of them, for re-use) by placing them in a kitchen oven or in a food dehydrator set to 180 degrees overnight. One safety tip: If your silica gel is in paper packets, then be sure to put it on a metal tray or cookie sheet to prevent the packets from falling through the oven grill and contacting the heating element. I presume that most of your reading this already own a dehydrator. They are great for making jerky and drying fruit. Every well prepared family should own one. The brand that I recommend (great for making jerky and drying fruit) is the Excalibur. We’ve had one of their large models here at the Rawles Ranch for 20 years and it is still going strong. Excaliburs are sold by a number of Internet vendors, including Ready Made Resources.