Make Clear Ice Cubes

While you are making glow in the dark ice, why not make some clear ice? There is a 'trick' to making clear ice cubes, but it isn't complicated and doesn't require an expensive restaurant ice machine. You need pure water and you need to control how it cools. The icemaker in my freezer has a water filter, but the ice cubes that it makes are opaque. My filter is relatively new, so I think that water doesn't cool at the right rate to produce clear ice or else there is a lot of air in the water. The clear ice cube in this photo was made using bottled water that had been purified using reverse osmosis (distilled water would be fine). I boiled the water to remove most of the dissolved air. I have heard that ideally you want to boil the water, let it cool, then boil it again. I got good results just boiling the water once. I let the water cool slightly so that I wouldn't burn myself spilling it, then poured it into an icecube tray and put it in my freezer. My unscientific investigation confirms that you can make clear ice by boiling and freezing purified water. I tried another tray, this time chilling the water more slowly, but that ice was milky on the bottom and clear on top. I also tried to make ice with unfiltered tap water. Let's just say the results convinced me I don't want to drink water straight from the faucet.

What can you do with clear ice? I guess you can use it as a magnifying glass. I can't say that I recommend using an ice lens for reading, unless you are reading outdoors in the dead of winter. In a pinch, you can use an ice lens to start a fire. Also... unless you like the taste of quinine, clear ice tastes a lot better in drinks than glowing ice.

Photo: This ice cube is clear enough to use as a reading lens. (Anne Helmenstine)