Crystals III

[DougC]

- - - That reminds me, , ,

- - - At the store where I work, there's an open fish freezer. Normally the humidity freezes like regular freezer frost, just what you'd expect. But every now and then, it forms larger, solid, clear crystals - that look like quartz. Occasionally you will find "pincusions": 10-20 thin crystals growing out from one point, each individual being 2-3mm thick and 20-25 mm long. Once in a great while, instead of a bunch of little ones you'll find a few really big crystals: 8-10mm thick and 25-30mm long. The crystals always are perfectly clear, with perfectly flat sides. I know that the crystals formed there, because they often grow in between and across different packages of fish. I never see them in the daytime; only at night. I ain't ever seen the fridge at home do this. What's happening? - MC

[Nickrz]

I've never seen this effect, but I think what's happening is water vapor in the air is passing directly into the solid state (sublimation) and hence crystallizes in a very pure form (that is, without air trapped inside i.e. freezer frost).

The fact you only see this happen "at night" might have something to do with the air currents in the freezer - you said it was "open" and I assume you mean a "coffin" type. When the store is busy, the air around and in the freezer gets stirred up more often, preventing the undisturbed ice formations you describe. Just a guess.