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I don't see any possible explanation. If there's a crystallite at one orientation, why would a crystallite at another orientation start growing instead of more molecules just building onto the surface that's already there in the same orientation? Does the size of the crystallites vary as the reciprocal of the speed of movement of the boundary between the solid state and the liquid state?

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  • $\begingroup$ Another crystallite would start growing for the very same reasons that the first one. It is not like the first crystal to form would immediately send a telepathic signal throughout the whole volume of liquid to the effect "it's OK, I'm here, stop forming new crystals, wait for me to grow and reach you". $\endgroup$ – Ivan Neretin Jun 22 '16 at 4:39
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Embryo crystals spontaneously and independently form in a supercooled liquid. A crystal successfully growing in one location doesn't prevent others from growing elsewhere. As the temperature decreases, the rate of embryo formation and chance of successful growth increase, so at a low temperature you're likely to get multiple successful crystals.

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  • $\begingroup$ Actually, usually, only a very small part of a liquid gets supercooled before it begins to freeze if the heat is sucked out of it quickly and then after that, you get a migrating boundary between the liquid and the solid moving as a result of continuous suction of heat and the solid still forms in polycrystal form. I want to know why that happens. $\endgroup$ – Timothy Apr 23 '16 at 2:12
  • $\begingroup$ My Masters dissertation is on the control of supercooling by proteins. Are you talking about water or liquids in general? Water has unique properties. $\endgroup$ – gsurfer04 Apr 23 '16 at 10:22

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