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What Makes Ice Cubes Cloudy?

ice, ice cubes, freezing
Ice gets cloud during the freezing process because of how it freezes. (Image credit: Ice image via <a href="http://www.shutterstock.com" target="_blank">Shutterstock</a>)

Curious children, and adults with lots of free time on their hands, often notice that apparently clear water sometimes produces oddly clouded ice cubes. The main reason is that the (hopefully) crystal-clear water you pour into the ice trays is not as pure as it seems, containing small amounts of (hopefully) harmless suspended minerals and sediment.

Because all objects freeze from the outside in, the center of the cube is the last to solidify. Water free of minerals and impurities freezes first, pushing the cloudy parts containing the sediment (and tiny trapped air bubbles) toward the center. The result is a harmless (but not particularly photogenic) ice cube clouding.

Not only do ice cubes cloud in the freezer, but they also shrink noticeably after about a week or two due to sublimation, the term used for evaporation directly from the solid to gas phase.

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Benjamin Radford
Benjamin Radford is the Bad Science columnist for Live Science. He covers pseudoscience, psychology, urban legends and the science behind "unexplained" or mysterious phenomenon. Ben has a master's degree in education and a bachelor's degree in psychology. He is deputy editor of Skeptical Inquirer science magazine and has written, edited or contributed to more than 20 books, including "Scientific Paranormal Investigation: How to Solve Unexplained Mysteries," "Tracking the Chupacabra: The Vampire Beast in Fact, Fiction, and Folklore" and “Investigating Ghosts: The Scientific Search for Spirits,” out in fall 2017. His website is www.BenjaminRadford.com.