Half a croissant, on a plate, with a sign in front of it saying '50c'
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Evacuated Ice Cubes

 Create ice cubes that really suck
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I think a great novelty item would be hollow ice cubes, where the "hollow" is not air, but rather vacuum. OK, I realize there will be some water vapor, but close enough.

As such a cube melts in your drink, the wall becomes thinner and thinner until, with a delightful pop, it collapses. Great fun at parties!

Can such ice be made? I have a procedure in mind, but I've never tried it. By boiling water in a nearly- closed container, one can drive out the air. Then, seal the container while the water cools and you have water plus vacuum. Then if you freeze the assembly while rolling it around, ice will form on all sides, leaving a hollow center. Then somehow remove the container from around the ice.

—spiel, Sep 25 2003

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       You could make half-cubes in special trays, to get a precise ice wall thickness. Some ice machines may produce a workable half-cube shape. Then assemble them in a vacuum -- use a household food vacuum packer, maybe with a special ice-assembly attachment.
—Amos Kito, Sep 25 2003
   

       Well...I'm not sure if such ice can be made, but I just don't know how long it would last. If you decrease the air pressure on ice, it will pull the individual water molecules out of the solid crystaline configuration. You'll get some liquid water, and also some sublimation. So that vacuum would basically melt the ice cube from the inside out. And once water vapor particles filled the inner cavity, you wouldn't have much of a vacuum anyway.   

       It's kind of like how water boils at lower temperatures when you lower the pressure (which is why fighter pilots wear pressurized suits). The ice would simply melt at a lower temperature. Super-duper cold ice might work though...
—Overpanic, Sep 25 2003
   

       Oh right - "evacuated ice cubes" in *that* sense. Phew.
—hippo, Sep 25 2003
   

       Had me worried too.
—thumbwax, Sep 25 2003
   

       You are all wron,g you remind me of the 50s ideas of what space travel would be like.   

       "If you decrease the air pressure on ice, it will pull the individual water molecules out of the solid crystaline configuration."   

       No it won't, vacuums don't pull on anything.   

       "It's kind of like how water boils at lower temperatures when you lower the pressure (which is why fighter pilots wear pressurized suits). The ice would simply melt at a lower temperature. Super-duper cold ice might work though..."   

       Solids do not melt at the same temperature in vacuums as they do on earth, you mistake this for liquids boiling at lower temperatures in space.   

       kthx
—0_owaffleo_0, Sep 25 2003
   

       Just in case anyone ever asks me if I want an evacuated ice cube in my drink though, I'm going to say "no".
—hippo, Sep 25 2003
   

       hippo: that strange blue colour putting you off?
—yamahito, Sep 25 2003
   

       Just for the record, at 0 C, the vapor pressure of water is only 1/ 160 of an atmosphere.   

       Might it melt from the inside out? That's an interesting question. Keep in mind that water in "vacuum" melts at a _higher_ temperature than does water at atmospheric pressure; I'm not sure this situation is so simple though.   

       Also, sorry about the the use of the term "evacuated". Perhaps "vacuous" would have been better.
—spiel, Sep 25 2003
   

      

Well, I think this is a nice idea. Good for you, spiel.

I’m imagining a glass of iced tea, the ice is melting. Then puuuuushk... puuuuushk.... pushk... the cubes develop holes, sucking up the tea. Suddenly my glass of tea is now half empty.

Cool.

Oh wait, gosh no, now I see a problem. This ice is too light, the cubes are like ice balloons in the glass, they won’t sink—they just jumble up at the top. I try to drink but all I get is ice.

Hummmm....maybe you could add some weights to the ice. Ball bearings or something?

—pluterday, Sep 25 2003
   

       Absurdly difficult to make, given that ice containing compressed air will also melt with random snaps, crackles and pops, and is readily available.
—DrCurry, Sep 25 2003
   

       Ah, no, compressed air would not be the same. Although it might be fun for some if their drinks boiled over when the cubes let go of their gases, displacing the contents of the container. I’ll take vacuum cubes, please.
—pluterday, Sep 25 2003
   

       Nitrous Oxide-filled ice cubes?
—hippo, Sep 25 2003
   

       Ice cubes filled with sulphurous (eggy smelling) gases probably not a good idea.
—spinynorman, Sep 25 2003
   

      

Here’s a way to make a bunch of them. Make frozen hollow hemispheres. Put two arrays of the hemispheres facing each other. Blow steam between them. Press together.

The steam displaces the air and condenses on the faces of the hemispheres. When you press them together, the condensed water freezes to make a seal. The steam within the two-part sphere also condenses, leaving a decent vacuum inside.

The tray that holds the array of hemispheres can be the same tray that you froze them in. Of course, a two-part tray is needed to make the hemispheres, but I’ll leave that to you.

—pluterday, Sep 25 2003
   

       If I get my toung stuck in one of these thing I'm going to be mad.
—Dagwood, Sep 25 2003
   

       I suspect hollow spheres would hold the vacuum better than cubes. Perhaps you could call them Vacuum Balls ;)
—webchat, Sep 26 2003
   
      
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