On 15 Oct 2005 07:57:44 -0700, wrote:

inner metal container
outer metal container
something insulating between the 2.

I've never seen a (modern) firesafe with a mere "insulator" between the
two layers. Instead they use a plaster mix which can actually absorb
heat (it goes to separate off the water from the previously hydrated
plaster). For typical fire exposure durations, this gives better
protection than a simple insulator. OTOH, the plaster also releases
generous quantities of steam, so the _inner_ box should be vapour
resistant too.

One of the simplest and cheapest fire safes around is simply to obtain a
large commercial safe (cheap S/H if you can move it), then to line the
inside with around four layers of plasterboard, with overlapping joints.
As four layer plasterboard is pretty strong, then you can make these
into removable inner drawers. Documents inside are stored in tinplate
biscuit tins.

--
"When men die, their Maker may reward them for their efforts by allowing
them to live again as male dogs. Thus freed from inhibition, they can spend
a cheerful existence doing all those things they really wanted to do when
they were men."

Paneb, Foreman mason in the Valley of the Kings, circa 1190BC