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Ice cube trays come in two main varieties, plastic and
aluminium. The plastic ones, if you buy quality, make
getting the cubes out relatively easy. A simple
twist or two and you can usually manage to hook a
fingernail in enough to retrieve a cube. Aluminium is a
better heat conductor
and should freeze the cubes more
quickly, but it's inflexible, leaving banging the tray
down on the counter top the only viable cube removal
Solution: metallic mercury freezes solid at around -39C.
This is a lot colder than the standard domestic freezer,
which is around -20C, so we will need super-cold
compartment, or retrofit some form of heat pump. Once
we have that, we make our ice cube tray. The tray will
simple in design, just a plan tray half filled with
To fit into this is a ice-cube mould/mold which is pushed
down into the mercury and clamped into place. Now,
the whole shebang into the small -45C freezer
compartment we created earlier. The mercury freezes.
this point, you take it out, remove the positive-
displacement cube moulding lid and pour in water.
transfer it back into the -45C freezer compartment.
you'll have frozen water ice cubes in a frozen mercury ice
Here's the clever bit, you take the tray out and place it in
the regular freezer. At -20C the mercury will melt, but
water remains frozen. Mercury, being a lot denser than
water will flow down into the bottom of the tray, the
water ice cubes will sort of merrily float about on top,
easily plucked and inserted into a waiting glass.
[bs0u0155, Jan 22 2016]
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||You know, it's a real bummer that mercury turned out to
be poisonous. Otherwise it would be so useful.
||Hey, maybe it isn't poisonous. Maybe we were just told
that because "they" wanted all the mercury for
"themselves". "They" probably poisoned several batches of
mercury with some other poison in order to get scientific
studies from honest doctors to support this conclusion.
Add in a few legends about the mad hatter and there you
||//remove the positive- displacement cube moulding lid// <bangs lump of solid mercury repeatedly on the counter top> Damn! <bang, bang> It's stuck again <inhales subliming mercury fumes> Ohhh! <lump of frozen mercury comes free from lid, in pieces>
||//Damn! <bang, bang> It's stuck again <inhales subliming
||Ahhh, you've failed to account for my genius. Unlike
water, metals just get smaller and denser as they cool.
So the mercury becomes solid at -38.5C, then cools and
contracts as it approaches -45C, it will cool and contract
away from the mould. The positive displacement (I'm
going with steel here I think) insert will also cool and
contract in the opposite direction, upwards, because it's
held up by the sides of the tray... and all the little
inverse ice-cube dimples will shrink upward.