Protective materials

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• DIY Faraday cage

The 'resistance' of free-space is about 377 ohms, so the incoming (electric) waves are at this value. If the fabric is 3.77 ohms or less, the attenuation could be as high as 40dB. That is fine, as leakage through the face-hole will dominate. When the resistance rises to 377/32 = 11.9 the attenuation can only ever be 30dB, and I regard the garment as at 'end of life.' A 1 ohm resistance would give a maximum attenuation of about 50dB.

'Leaks' in the garment design become the dominant factor in the lower resistance fabrics. The face hole is at best 15dB (for signals coming from the back of the head), but it is more effective as the frequency drops to FM radio and below (due to the increasing wavelength the whole garment becomes more like a piece of 'wire').

Yes, I regard black #081 ('Soft and Safe') as being the most durable. But the new sleeping cap fabric (in light brown) - engineered to be a little more resistant to sweat - does seem to have caught up, and is an option if you don't like black, or want to save a few dollars (I don't have a price on the new fabrics yet, but they should be a little cheaper than the #081). You must expect to replace the outfit every few months if you wear it 24/7, as the resistance will slowly rise over time, as the silver is worn off the threads.

- Dr Marshall, 31 December 2017 04:49

Window film isn't a very good shield, although it does retain its performance to very high frequencies. Typically you only get 25dB from a commercial window film. The very best I have seen is 45dB (that was a military film), with the high-performance varieties averaging 35dB. That is way below what aluminum attic-foil can give (in excess of 55dB, probably about 70dB). Close-mesh stainless steel approaches that level of performance at lower microwave frequencies, but I am not sure how important the higher frequencies are at this point in time.

- Dr Marshall, 29 April 2017

It has been some time since I looked at the HEG03. That time has seen millimetre wavelengths explode in importance. It has also seen our new #92 fabric, and the resulting understanding that good shielding really works better…

I did test the 50mesh (50 threads per inch) stainless steel mesh that we were using for see-through shielding, and it is essentially transparent (less than 15dB) at 40GHz, worse at 60GHz. It looks from the yShield website that their new mesh is approximately the same wire pitch (0.5mm).

I also saw diffraction and other resonant effects with mesh at high frequencies :)

I am not saying “do nothing,” I am urging a closer look at getting hold of aluminum sheeting / foils.

- Trevor, 24 April 2017

As Mike says, the #66 silk-based fabric is less warm than the sleeping hat 78#B, and seem fairly durable.

- Trevor, 6 December 2016

The 100 mesh 0.0012 is significantly less transparent, although still better than Silver 30#, and we haven't had trouble with it bunching up yet (but I haven't used much). There is an 80mesh, haven't looked at that yet. Still trying to make the 50 mesh work out OK.

- Trevor

• Soft N Safe: A bamboo fabric with silver thread woven into it that has a soft hand feel and seems to shield signals from some frequencies better than others. (see this for details of a similar material: 70% bamboo fiber and 30% Silver). The material I used was a custom version where the fabric is black. We are not sure about durability for this material.
• Staticot: A cotton/polyester blend fabric with microfine stainless steel fibers (see this for details: low cost, tough fabric ). I liked this for a sleeping tent because it has more structural stability (on the floor of the tent), has a pleasant color (spring green) and is very durable.
• 78#B: This is the fabric we used for the SLEEPING CAPS. A bamboo fabric with silver thread that has a lighter weight and greater durability than Soft N Safe. This fabric is one of the best for shielding the range of frequencies needed for recovery.
• #92: This fabric is a silver 4 way stretch knit that is less durable than 78#B and yet has been found to be very comfortable for daily wear. It performs the best of all the fabrics for shielding over the whole range of frequencies we have been able to test. It does not provide as good of structural support on the floor when used as a tent.
• AtticFoil (technically not a fabric): This material provides excellent shielding performance while also being very durable. While it does have microperforations, it does not provide any ventilation, therefore another material must be used to allow a small fan to blow air into a tent made from this material.

-Joyful

PRO for #30: #30 is somewhat see-through #30 is good for curtains, insert into screen for window coverings #30 may work for a veil over face when traveling on high EMF freeways #30 allows air flow and may be more comfortable to wear in warmer weather #30 costs less than half the price per square meter compared to #92

CON for #30: #30 is reported by some members to cause irritation when worn against skin #30 loses it's silver quickly when stretched in normal wear (not stretchy) and will need replacing much sooner than #92

PRO for #92: #92 lasts much more than twice as long when stretched in normal wear (4-way stretch) #92 is reported by some members to be comfortable, soothing when worn against skin #92 has a cleaner look when made into clothing

CON for #92: #92 is breathable, but may be less comfortable to wear in warmer weather #92 costs more than twice the price per square meter compared to #30

-Joyful

I agree with all Joyful says :) :) My comparison: #92 has 10 times (10dB) the shielding of #30. This is especially noticeable at higher mm frequencies, such as are used in automobile radar systems these days. The body's own internal sensitivities are also weighted towards the higher frequencies.

Bottom line: I now only use #30 on windows, etc, not clothing.

- Trevor

“30dB is pretty high for fabrics, IMO. We need to go to sheet metal and mesh to get much beyond that. When I measured the fabrics, etc, here in my test setup, I found the fabrics giving 35-45 dB average in ideal conditions. Only the aluminum foil and mesh achieved better than that. The Foil was better than 60dB while mesh performance depended on weave because I didn't have really good RF meshes at that point.” Double layer of #30 can give up to 50dBm, which is good.

- Trevor

Date: 2016-05-06 04:22:39 Reply: https://marshallprotocol.com/reply.php?topic_id=16583

Mike, the HEG03 is the stuff coming to make the Faraday cage out of.

The mesh for front of the driving-hood, etc is here: 50 mesh It shields very nicely, >50dB at 1Ghz, >40dB at 5GHz (>70dB below 100MHz).

The stuff which came today was this: 100 mesh and it is four times as dense, but still 80% transparent and handles like cloth. This stuff shields to 70GHz, to handle the new anti-collision radars

https://www.twpinc.com/media/catalog/product/cache/1/image/9df78eab33525d08d6e5fb8d27136e95/h/i/high-trasparencywebready.jpg

- Trevor

Date: 2015-11-27 21:00:45 Reply: https://www.marshallprotocol.com/reply.php?topic_id=16452

So aluminum is more effective than the yshield paint?

-Rico

Date: 2015-11-27 21:53:50 Reply: https://www.marshallprotocol.com/reply.php?topic_id=16452

Oh yes. The 5ft (and even 4ft) wide rolls of two-sided aluminum (from attic-foil.com) shield very well indeed. Only problems are conductivity between panels of the sheeting (needed at low frequencies) and gaps at the corners of the room. I use a 1 ft overlap with 5ft wide rolls to try and minimize conductivity and leakage problems.

yShield works remarkably well. Again, the leaks at corners and edges tend to let more signal in than gets through the paint layer itself (which is rated at 38dB). The attenuation does not measurably change when you put a layer of 'normal' undercoat over the top.

- Trevor

Date: 2015-04-21 05:10:10 Reply: https://www.marshallprotocol.com/reply.php?topic_id=16241

The best shielding is either 1/8“ mesh or 1/8” circles in a flat sheet, which you can put over the vents with at least 6“ overlap all around. The holes in this are a little big, but should do OK at 2.4Ghz for 15-20dB or so: 36 in. x 36 in. Cloverleaf Aluminum Sheet

You can also use 'expanded' aluminum like this, as lone as the 'holes' are less than 1/4 inch diameter: 36 in. x 48 in. Expandable Aluminum Sheet

- Trevor

Dr. Marshall, Some cloth is not conductive but does provide measurable shielding. The 'Jersey Cotton' fabric and the 'SwissSield Naturell' fabric are both not conductive but have a significant shield effect. So, I am unsure what is at play there.

-Mike

You are correct, I have a sample of Naturell and that seems to be isolated strands of copper, rather than a mesh. I am not sure how to assess the shielding of such a fabric, as it doesn't follow the Faraday Cage model…

- Trevor

The #30 mesh and HEG03 have similar attenuations, with the HEG03 being perhaps a little better. But I doubt if we could measure the difference. I will try a small cage out of #30 in a week or two, just to compare. Obviously the stainless steel mesh is rigid, stronger, and should last 'for ever.'

- Trevor

The paint used is Y-shield HSF54

paint for interior and exterior shielding

plus the additive AF3:

additive

It is important not to paint it onto surfaces that are coated with the more natural mineral-based paints, or to use these to cover it. Ordinary household emulsion paint is fine. It may take 3-4 coats to cover the Y-shield, unless you like having black walls

The surface you are painting onto must not be porous otherwise the shielding will be compromised. This is unlikely to be a problem over existing paint and wallpaper, but would matter over new plaster or plasterboard. Yshield recommend you test a small area. If you get a silvery/shiny rather than a matt black finish, the surface is too porous and will need priming/painting/sealing.

It also doesn’t make sense to put Yshield over paint that is flaking or surfaces with cracks. I had both of these issues with my bedroom ceiling, but coincidentally had just fixed exactly the same issues in another room. For fixing the slightly flakey/porous /chalkysurface, I used a specialist paint, Zinsser Peel Stop - binding primer (My experience with all Zinsser products has been great. they aren’t cheap but they do work). Once that was on, I used a specialist ceiling paint to deal with the cracks: crack-free ceiling paint I had already used this successfully in the other room. It’s water-based and matt, but thick and sticky and covers up hairline cracks really well. I dealt with one bigger crack with acrylic filler. I also filled any cracks in the join between wall and ceiling with acrylic filler, which Yshield seems to cover well.

Mixing and the fibre additive

Yshield depends on carbon particles for its effectiveness, but if the tub stands still for any time, the carbon concentrates in the bottom, so mixing is very important. I wouldn’t want to do it by hand, and I used a thing like this, which fits in my Bosch cordless drill/driver: Mixing-Paddle

A lot of mixing is also needed to get the fibre additive evenly distributed within the paint. I used a whole jar of the fibre additive for each 5 litres. It’s black, sticky and fibrous and sits in clumps in the paint unless you mix it in very well. Again, I wouldn’t want to do it by hand.

The fibre additive is recommended by Yshield for surfaces that are cracked or imperfect, but I think I would use it on most surfaces. My reasoning for having it was concern about the joint between the ceiling and the wall. The idea is that it might help by adding thin carbon fibres across the seam. It certainly seemed to help the paint stick in the joints.

When Yshield say black, they really mean black (if it was hexadecimal, it would be #000000). So although brushes and rollers wash out with water, it is messy stuff to cleanup, and I can’t imagine using the brushes, rollers and tray for any other kind of paint once I’ve finished.

Covering it:- only certain types of paint can go over the top of it, so I’ll be doing some investigation and testing. But the finish is very soft and marks very easily, so needs covering up otherwise is likely to become damaged.