A while back, I posted a lengthy description about How To Make Ice Spheres. If you recall, spheres of ice that fill your glass originated in Japan where they are hand-carved behind the bar. The large spheres keep drinks cold with very slow dilution. Not wanting to risk slicing a finger, I opted for alternatives to carving, but the best alternative is a very expensive ice melting device. So, I explored slow-molding options and until recently had settled on a two-part 3-sphere ice tray to pull this off. My tedious process often involved refreezing mis-shapen "eggs" in order to get the proper spherical aesthetic—until now!
Enter the Muji silicone Ice Ball mold. This unique and inexpensive mold does a fantastic job making spheres without the problems and hassles associated with a thin plastic tray. I was so happy to finally see these in stock at Muji online again that I bought two of them. Muji used to sell a similar item that had a cylindrical outer shape, but for some reason it disappeared for a couple of years. I was always disappointed and dumbfounded that this unique item which has such potential could be unavailable for so long. I even considered trying to make my own. Well, Muji finally came through with a new version that isn't stackable, but perhaps takes a little less room in the freezer.
The two-part silicone molds fit snugly together. The bottom half is flat on the outside so it won't roll around. The top half has a hole at the top used for filling with water. The hole is about as big as your pinky finger, so there's plenty of room to fill it from the faucet. Once filled with water, you press the mold halves again to ensure it they are sealed and seated properly. Once frozen, it's a simple matter to peel the flexible mold open and reveal your perfect spherical ice!
There are a few tips in the instructions that are helpful. First, the slower the ice freezes, apparently the better the appearance will be. Also, boiled water will have fewer air bubbles. I didn't even bother to test this and went straight for the tap. I figured it might help set my expectations lower if I went the easy route first. Finally, you don't actually fill the mold completely. Leaving just a tiny bit of airspace at the top of the sphere will allow for expansion. My molds have all pushed ice through the hole at the top, but this is a much easier problem to deal with than a mold that separates and expands into an egg. For me, the mold stayed together nicely and the spheres were usable on the first freeze.
Because I don't use them every day, I wrap my spheres in plastic and place them into a ziplock bag. This keeps them from absorbing odors and from sticking together. Ice also tends to sublimate over time, so keeping them wrapped in plastic maintains their size and shape until needed. Nothing impresses guests more than a classic cocktail served with a giant sphere of ice in the glass, and Muji just made that a lot easier for all of us!