What would be the best metal to use for a blech — one that conducts the heat and withstands the high temperatures without being damaged?
A blech, by definition, is tin. That’s what the word means. If you make it out of copper then it’s a cooper, not a blech.
Beryllium might be good too, though I have no idea where to get it.
Are you making your own blech?
Gerufa u’tmuna can be accomplished by any covering of the fire and he’ker – in past tin was used because it was cheap and easy to use, but any material (for safety – fireproof and heat conducting) can be used.
BTW – A layer of aluminium foil would not be “kosher” for a blech because it would be bottel to the oven (unless several layers are used).
Seriously though, I believe the ones that are commonly sold in stores are galvanized steel (similar to the air conditioning ducts in houses, but thicker).
Based on thermal conductivity, melting point, and cost, it seems to be the most reasonable option.
Copper is the better conducter but way more expensive
I just read that Beryllium is very toxic, so I would ditch that idea.
Solid gold would be the best conductor. At current prices a slab 60 by 60 cm and 2mm thick would only be about $30,250.