When I pulled out the ice tray to make a whiskey lemonade over the weekend, I couldn't help but notice that the ice had a cloudy white spot in the middle of it. This prompted me to ask: why is it that some ice I buy at the store is crystal-clear, but the frozen cubes at home in my freezer appear murky and white in the center?
Ice cubes develop cloudiness when water is frozen quickly. As ice begins developing on the surface of water, certain gases can no longer remain dissolved and begin to surface as microscopic bubbles. An already-developed outer layer of ice traps all the bubbles inside the frozen cube. Another reason for the white color may be traces of calcium carbonate or impurities, which are small and flaky in appearance but are completely harmless.
Ice makers are able to achieve a clear, see-through effect by distilling water, then freezing it in stages, and by using a mechanism that allows bubbles to be washed away as ice cubes develop.
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Vanessa Bruno
Interesting..
1Much of it is impurities within the water. If you see an ice sculptor work you will see that when they freeze their large blocks, they will have a metal bar (zinc, I believe) down the center of the block as it forms. As the ice forms the impurities will be drawn to the bar. Once completely frozen the bar is removed and the entire large block is crystal clear.
2Interesting!
3I've ALWAYS wondered about this!
4I never knew. Thank you. I feel as though I've learned something scientific today.
5Thank you for this, I remember asking myself this very question one lonely night when I was totally drunk.
6Yeah, the impurities make a difference. I can always tell the rare occasion that my housemate fills the ice trays.
He always uses tap and I fill using Brita filtered water. Additionally, he usually overfills it and the cubes are all connected instead of individual cubes.
7Boiling your water (and cooling it) before freezing will produce crystal clear ice-- try it! It's all about the dissolved gases, which boiling forces out of solution. Remember: if you're not part of the solution, you're part of the precipitate.
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