The kind that was used in Mythbusters to construct a faraday cage. I live in NorCal and have called several hardware stores to no avail.
Contact your local screen door manufacturer.
Most will sell “copper” flyscreen mesh or “stainless” security mesh that will suit your purpose. Note that copper flyscreen is usually made of bronze wire, while stainless security mesh can be almost anything from plastic coated copper to genuine stainless steel.
I googled “brass wire mesh” (quotes and all) and came up with about 81K hits. I checked the first two pages of links, but none of them were companies I’ve had any experience with, so I can’t recommend any in particular. My understanding, though, is that any wire mesh will do for making a Faraday cage (of course, I could be wrong).
McMaster-Carr is a good starting place for obscure hardware that Home Depot doesn’t carry. In this case, type in “wire mesh” and use the blue down-select links to narrow your search, or go straight to catalog page 357. I’m using their website to compile a parts list for the trebuchet I’m building. I also used them extensively for my undergrad senior design project: a patient-propelled lifting/tilting backboard for disabled patients. If you can’t buy it from McMaster-Carr, you might be buying the wrong thing.
Pretty much, so long as the size of the holes is significantly smaller than the wavelength of any radiation you’re hoping to shield, and also smaller than the distance of anything you’re trying to protect away from the cage. More conductive metals will work better, which means that, of the cheaply-available metals, copper or aluminum is probably your best bet.
I second McMster - Carr. They sell everything and then some. Been using them 25 years and never disappointed.
Good electrical connection at the seams is important. Copper and brass are easy to solder. Aluminum, stainless, galvanised steel, etc are not. Aluminum, in particular, self passivates, making good electrical connections problematic.
Electric fields are easier to shield. Magnetic fields are tougher, making the conductivity of the shielding, and the seams more critical.
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