hark 2021

[Andy W]

Just a cell phone photo - but I can't explain this. :beguiled:

I fill these small paper Dixie Cups near to the top with water and freeze for Dixie Cup Ice Massage. It's used in physical therapy to help reduce inflammation. I've been freezing these since the late 1980's after my third knee surgery. But ... but how??? :highly_amused: It didn't tip over at any time in the freezer either.

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I asked my son about this since he worked in icing research:


I saw this rarely when working with ice in a vacuum at work trying to make samples. When water freezes, it expands. When you stick a warm cup of water in the freezer, it freezes from the outside in. Same thing for water in an ice cube tray. Since it forms a shell and then continues to freeze, it creates quite a lot of pressure inside the ice. The outer layers typically stay clear; they're formed at low pressure and dissolved gasses don't build up there. The inside gets cloudy as gasses are pushed out. Anyways, as the pressure builds, it can help create a hole at the surface and form a straw. As the water comes out, it freezes and lengthens the straw, and you can get a long spike.

See this Wikipedia article (they're saying a hole is left at the top in the freezing process, which sounds plausible to me): https://en.wikipedia.org/wiki/Ice_spike

 

[hark]

I asked my son about this since he worked in icing research:

I saw this rarely when working with ice in a vacuum at work trying to make samples. When water freezes, it expands. When you stick a warm cup of water in the freezer, it freezes from the outside in. Same thing for water in an ice cube tray. Since it forms a shell and then continues to freeze, it creates quite a lot of pressure inside the ice. The outer layers typically stay clear; they're formed at low pressure and dissolved gasses don't build up there. The inside gets cloudy as gasses are pushed out. Anyways, as the pressure builds, it can help create a hole at the surface and form a straw. As the water comes out, it freezes and lengthens the straw, and you can get a long spike.

See this Wikipedia article (they're saying a hole is left at the top in the freezing process, which sounds plausible to me): https://en.wikipedia.org/wiki/Ice_spike

Thanks, Andy. And this makes sense. When I took photos of an ice jam on the Delaware River, I remember hearing the ice *groan* and creak as sections of ice shifted against other pieces of ice. The entire river was covered with small mounds of ice - not flat at all. So perhaps the ice freezing there is applying the same principles you explained.