Now the bench. A continuous metal skin around a space blocks the fields crossing it — and you can make one from foil, mesh, or a tin in an afternoon. Here's how to build one that actually works, and how to prove it does.
Kitchen aluminium — cheap, total coverage, great for small full-block boxes.
solid & cheapWindow screen or hardware cloth — breathes, you can see in, blocks most RF.
breathesA paint can, cookie tin, or ammo box — a ready-made cage with a lid.
ready-madeSilver/nickel cloth — flexible bags and pouches for phones and keys.
flexibleSeals seams and lines small boxes — keeps the skin continuous.
seals seamsConductive gasket or finger-stock at the lid — the part most builds get wrong.
the lidTwo snug layers of foil kill the signal — the 30-second proof.
need aluminium foil · a phone
do wrap fully, no gaps; call it — it won't ring.
+1 overlap the foil seams generously; a single open slit is a leak the signal walks right through.
Drop a phone in a metal tin with a tight lid.
need a metal tin + lid
do seat the lid fully; the better the metal-to-metal seal, the deeper the silence.
+1 a painted or plastic-rimmed lid breaks contact — sand the rim to bare metal for a real seal.
Line a box inside and out with foil for a roomier cage.
need a box · foil · tape
do cover every face, bridge the seams, foil the lid's edges too.
+1 the lid must touch the body's foil all around — tuck a foil flap so the seam closes when shut.
Conductive fabric sewn into a fold-over bag for keys or a phone.
need conductive fabric · a fold-over closure
do overlap the fold several times so the opening seals.
+1 these are how car-key fobs are blocked to foil relay theft — a real everyday use.
A frame skinned in screen — a see-through cage you can work in.
need wire mesh · a frame · conductive fasteners
do bond every panel edge to the next; no insulated gaps.
+1 mesh only blocks waves whose wavelength is much bigger than the holes — fine mesh blocks higher frequencies.
Continuity across joints is everything — a seam is a slot antenna.
need copper tape / conductive gasket
do tape or gasket every seam so the skin is electrically one piece.
+1 a long thin gap leaks far more than a small round hole of the same area — close slots first.
Any opening is the weak point; the lid needs to make contact all around.
need conductive gasket / finger-stock
do ring the opening with gasket so it closes the skin when shut.
+1 this is exactly what the springy fingers around a microwave door are doing — copy that.
Getting power or signal in without wrecking the shield.
need a filtered feed-through / bulkhead connector
do never run a bare wire through — it carries the field straight in.
+1 an unfiltered wire through the wall acts like an antenna on both ends, defeating the cage.
A cage shields even ungrounded — but grounding gives stray charge somewhere to go.
need a ground wire (sometimes)
do ground it for static and safety; for blocking RF, continuity matters more than ground.
+1 common myth: a cage "must" be grounded to work. For field-cancelling it doesn't — the shell does that itself.
The easiest check — does a call get through?
need a phone · a friend to call it
do seal it in, call; no ring = the cage holds at that band.
+1 test each band separately — a cage can block WiFi yet leak lower-frequency cellular, or vice-versa.
A radio inside should go silent when the cage is sealed.
need an AM/FM radio
do tune a station, close the cage, listen for it to drop out.
+1 AM (long wavelength) is harder to block than FM — if AM dies, your skin is genuinely continuous.
For real numbers, compare signal strength inside vs out.
need an SDR / field-strength meter
do read the level, seal it, read again; the drop is your shielding.
+1 shielding is rated in decibels (dB) — every 20 dB is a 10× cut in field strength.
A small shield can box in a part that radiates interference.
need a metal can over the circuit
do contain the noise at its source so it stops bothering neighbours.
+1 those little tin cans soldered onto a phone board are exactly this — shields over the noisy bits.
Shield a sensitive measurement from outside RF.
need a cage around the setup
do block the room's hum and radio so your signal is clean.
+1 mains hum (50/60 Hz) is partly electric-field pickup — a grounded shield around the input tames it.
A pouch stops thieves amplifying your car key overnight.
need a signal-blocking pouch
do drop the fob in; no signal escapes to be relayed.
+1 test it — many cheap "faraday pouches" leak; if your phone rings inside, so does the fob's signal.
The oven's mesh door is a Faraday screen keeping the microwaves in.
need just look at the door
do see the holes — small vs the microwave wavelength, so the waves can't pass.
+1 never run a microwave empty or rely on a damaged door — but the door itself is a textbook cage.
workbench series · no. 1 · a cage is only as good as its worst gap · seal the seams, test the result