BrainStuff Classics: Why Does Ice Get Cloudy?

When temperatures dip below freezing, it adds a number of extra hazards to driving, but perhaps none so tricksy as black ice. These are slick patches of ice that blend in with the black pavement beneath them because they're so transparent. When drivers, blind to the danger steer their cars over the ice, they can lose traction and wind up in an accident. Other kinds of ice are easier to see.

You've no doubt noticed that homemade ice cubes usually look cloudy in the little opaque in the middle, like whitish blocks of cotton candy. That stands in contrast to the frightening clarity of black ice. So how come black. Ice is see through, but the cubes and your typical ice trays are not. Liquid. Water appears to be clear. That's because the material neither absorbs nor reflects most of the spectrum of visible light. Most wavelengths and spectrum pass right

through it. And that's right, I said most. Technically, water is not colorless, although it often looks that way. Believe it or not. The liquid has a natural bluish tint, owing to the fact that it absorbs red, yellow, and orange light more easily than blue light. But our human eyes can only observe this azure quality in deep bodies of water. This helps explain why ocean water in glacial ice look blue to us, while glassfuls of drinking water

look transparent. Yet there is a deceptive quality to water. No matter how fresh and clear it may seem, it's never one hundred percent pure. A sample of H two O might contain floating bits of organic matter like algae or plant remains, along with suspended sediments, a dust, particles, or flex of minerals like calcium and lime. It may also harbor lots of dissolved gases, such as oxygen. Without

said oxygen, fish wouldn't be able to breathe. A Gases and physical impurities are the key to understanding why those ice cubes in your tray are so darn cloudy. When water freezes, internal debris and air bubbles can become concentrated the cluster's impede light, causing all the differently colored frequencies on the visible light spectrum to scatter. When this happens, it makes the ice look white and clouded. But it doesn't always happen. Let's take for a case study, a

YouTuber who once appeared to walk on water. In twenty fourteen, Thomas Nunnak filmed himself in a travel companion walking across velke Hinkovo Pleso, a deep freshwater lake in the Slovakian Mountains. His video went viral because it shows the two men standing on some unbelievably clear ice. The lake bottom rocks

below them are pristinely visible through frozen water. The ice in linux video was so transparent that some viewers assumed the footage had been faked, but the phenomenon is very real, and when the lake freezes over, as it often does, the surface ice can be crystal clear. An ice sheet needs to be almost entirely free of both air bubbles and debris. In order to have this degree of clarity,

there are other requirements as well. Ice is made up of crystals, and when water freezes rapidly, those crystals tend to be small and numerous. That makes the ice look whiter because each of those crystals have reflective surfaces, so if there are more crystals, there'll be more reflection going on, which will help scatter in coming light. On the other hand, ice that's been slowly frozen is built out of fewer

and larger crystals, and those promote transparency. So ice will only be see through and crystal clear if it freezes slowly and doesn't have too many impurities or crystals. Thomas Ninnock's now famous YouTube video is what it looks like when all these conditions are met. On the day of his track, the lake was topped with an icy blanket that was around two centimeters thick that's about three quarters

of an inch. The water must have frozen gradually during a tranquil period with no strong winds to deposit debris in the lake or to churn up the water. We see the same kind of thing happening in roadway black ice. Although Not all of this stuff comes from the same source. It can start out as fog, mist, drizzle, or melted snow. It always freezes slowly during low wind periods. It's consistently thin, and it contains very few impurities. That's why black ice

is so transparent and frustrating to motorists, but highway annoyances. Nonwithstanding, transparent ice isn't as common in nature as the white clouded variety. There are a lot of reasons why a given ice chunk you find out in nature might not be clear. Some ice is made up of fallen snowflakes, whose angular shapes and irregular crystals scatter light, and sometimes temperatures drop rapidly, resulting in ice with those smaller crystals.

Artificial ice is subject to these same physical laws. A Most household ice trays are designed to freeze little blocks of water from the outside. In doing so has the side effect of driving impurities within the water toward the center of each cube. The finished products therefore look white and hazy in the middle. To get clearer, more attractive cubes, some restaurants use expensive machines that freeze water very gradually

and exclusively from one side that lets the impurities escape outward. Though, if you want to make clearer cubes at home, you can do it on the cheap. Try boiling the water first, thus ridding it of dissolved gases before the freezing process starts. Just let it cool of it before you add it to your ice tray. You wouldn't want to melt the plastic. Today's episode is based on the article why ice usually freezes cloudy not clear on HowStuffWorks dot com, written by

Mark Mancini. Brain Stuff is production of iHeartRadio in partnership with how stuffworks dot Com and is produced by Tyler Klang. Four more podcasts from my heart Radio. Visit the iHeartRadio app, Apple Podcasts, or wherever you listen to your favorite shows.