IronGoober
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Oh, ok. I only watched a short part of the video, but it makes sense.
So the reason you want to freeze it slowly is to keep the solidification front planar... and you want it to be directional solidification. If it freezes fast, the ice forms dendrites and can potentially trap stuff in between them. Dendrites cause all the stuff that isn't the perfect crystal to get pushed into the liquid in front of the growing dendrite, but this stuff can become trapped because of the funky shaped nature of the growing dendrites. When people grow Si crystals, the solidification front is planar, so you end up with a perfect crystal. The directional bit can be accomplished just by insulating the whole thing and keeping the opening exposed. But planar, directional solidification will end up with the most perfect crystal formation,pushing most contamination out in front of the crystal until the last liquid forms ice, trapping all the contaminants there.
Having contaminants like gases and mineral in the water can serve as nucleation points for new ice crystals that causes new crystals to grow, potentially leading to cloudiness. (which is from crystal grain boundaries possibly?)
I made a comment on your video Joe, but I think the directional solidification will do the trick.
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Making ice balls with boiled water (Read 151 times)
