At one point or another, I've done most of what you suggested.
Stainless or aluminum sheet would work just fine, copper'd be pricey
as hell, and straight steel would rust, but be fine if you painted
The thing about the table is that you're not planning on *leaving*
anything hot on it, so you don't need to worry about the wood
underneath, unless a hot crucible sits still on the surface for more
than 5-10 seconds. Spatter from a blowout or missed pour will cool
off too quickly to do much damage, unless you're doing *huge* pours.
Steel takes a fair bit of energy to get warm, and it doesn't
transmit heat nearly as fast as the non-ferris metals do, so you've
got more time than you think before things start to fry. Aluminum
and copper would transmit much more quickly, as well as reacting
with the metals you're most likely to spill.
For an ingoting area, I would lay firebrick on top of your metal
shield, because you can get large slugs of molten metal there.
For the centrifuge, I'd absolutely, positively, get some sort of
shield to go around it. Centro's don't throw the spray down when
things go wrong, they throw it out and away. Which means you really
want a containment wall to catch all that expensive, fire-starting
metal. The Frei's have one, and I expect everybody else does too.
My machine lives in the top of a 55 gallon drum that I turned into a
combination blast shield/casting machine/ballast system. (The
traditional american base for a centro was a 55 gallon drum 3/4 full
of concrete, with the cento bolted onto the top of the concrete, but
still a foot down from the top of the drum. Weighs about 600 pounds.
Which means that centro is *NOT* going to vibrate itself.....
anywhere at all. The problem is that it weighs 600 pounds like that.
Predictably, mine is fancier.
55 gallon drum, with the bottom 2/3 of a heavy plastic 55 gallon
drum liner. (I was living in a place with an industrial plastics
company that had this stuff on hand, and available as seconds, for
almost nothing.) (US Plastics, Lima, Ohio.
It's been nearly 20 years, so I can't remember exactly which of
their containment tanks I frankensteined, but you get the idea. )
So I've got about 35 gallons of water in the bottom of the drum, in
a plastic tank, with a pair of faucets to let the water in and out.
3/4" plywood deck on top of the tank, with the centro bolted into
the middle of the plywood deck. In use, with the tank flooded, it
weighs about 300 pounds. Still not going anywhere, especially since
the water acts as a tuned mass damper, and actively works to
counteract any vibration from the centro. The truly wonderful thing
about it is that when I move (which I did a lot back then) I can
dump the water, and suddenly the thing weighs. not much. Just the
weight of the drum, basically. Not 'pick it up and walk away with
it' light, but nowhere near 600 pounds of concrete. You can also put
a slab of plywood across the top of the drum when you're not using
it, and turn it into a table. Very handy.
To be honest, I don't remember if I shielded the top of the wood
with anything or not. That particular centro didn't make the move
out to California, so it's been sitting in storage back in Ohio for
years. One of these days I'll settle down and get the rest of my
crap. (Which is why I scratchbuilt a basic vac caster out here...)
Ah the joys of the Tenure Trail, once upon a time....
PS"> to get back to what Ron asked about originally, I've put hot
flasks on offcuts of marble countertop with no adverse reactions. We
used them to shield the tabletops around the enameling kilns at the
Santa Barbara program. Never had a problem, and marble shops usually
have all sorts of random square-foot-ish sized pieces laying around.
Too big to trash, not big enough to use for much.
Not a bad idea, but wear a face shield the first time you put
anything really hot on any given piece. You just never know.....