Craft ice is a thing

My brother-in-law and his family visited this year for Christmas, which was fantastic. Knowing my enthusiasm for mixology, he brought me a clear ice contraption that makes perfectly clear cubes. They don't make your old fashioned any colder, but they sure look cool. It's an insulated thing that makes "throw away" cubes at the bottom, and clear cubes in the top inside of a rubberized (silicone, I assume) compartment. The insulation is open on the bottom. Because of the way it freezes, it pushes the rubberized part, with a cover, up, but it means the rubber bits are touching all sides of the cube.

Naturally, I wondered what the physics were here. Unfortunately, the Internets are mostly wrong, as most people insist that this somehow forces the "impurities" out of the water. This is one of a hundred myths perpetuated by bartenders who don't really get into physics and chemistry. In fact, a bartender recently insisted that carbonation causes alcohol to be absorbed faster into your bloodstream. (There have been small studies, and while there is possible correlation for a subset of drinkers, there is not causation because the studies do not control for sweetness or rate of consumption. You can infer why that makes me skeptical of causation.) Anyway, a significant portion of "impurities" are already gone from my water, because it's filtered where it enters the house. If it was more "pure," logically my regular ice cubes would be clearer. They are not.

Getting deeper into it, these insulated gadgets cause the water to freeze more slowly, and if I'm reading it right, that means the gases inside of the water are forced in one direction away from your "perfect" cubes. That makes more sense to me. If there were significant impurities in the water, I think it would be cloudy as a liquid as well.

This isn't the only neat trick though. On our last cruise, they had drinks on the menu that included spherical ice, hollow in the center, with a hole, that they would put part of your drink in. Then you got to break it with a little hammer. Neat. The spheres are made by using round silicone molds. After a certain amount of time, when only the outside is frozen, they peel open the mold, run those very same hammers under hot water, and push a hole into the sphere, allowing the unfrozen water to pour out. Then they go back into the freezer.

So yeah, craft ice is a thing.