Aluminum sounds easier to work with. What about those fire safe bags + aluminum sheet? Seems like easy and fireproof enough.
I checked some of those fire safe bags and guess what, they are also made from aluminum foil mixed with some pvc, so I don't think it's a good idea to wrap aluminum with more aluminum.
Some of them have Fiberglass and that is good material for isolation and have melting point around 2500 F or 1370 C
Thank you everyone for your answers.
Is stainless that much better than copper?
How about brass?
Here are some melting points for mentioned metals, but you need to calculate the price and then you can judge for yourself:
Aluminum 1220 F or 660 C
Aluminum Alloys 865-1240 F or 463-671 C
Brass 1650-1880 F or 900-1024 C
Copper 1983 F or 1084 C
Stainless Steel 2750 F or 1510 C