Thought of another.

If you need to cool something off quickly-sodas in a cooler for example, instead of just ice, add water.

The water increases contact and allows the what-ever to cool by conduction rather than radiation.

This also applies to cooling things like boiled eggs or custards or if you’re doing ice cream the “old way”, getting it started faster.

Also if you find you need crystal-clear ice, say for cocktails, you can make your own mold using a thermal or insulated cup and casting silicon resin. Get whatever you want to use as a positive for the mold, if you want spheres, a racquet ball or squash ball works well. Then, attach a straw with some glue- hot glue works, Elmer’s or CA. Doesn’t really matter.

You will need a second positive that goes into the bottom of the mold and has another straw between the object you want, as long as it creates a large space with a small void between them (a half an inch on straw length,) you can make this with crumpled up paper or something. It doesn’t need to be pretty. Just about as large as the positive you want.

Set that positive up in the mug exactly how you want the ice to form- something to keep the mold and straw centered helps. String held in place by the lid works.

You will also want to know about where the positive is widest. If you’re molding something cubed or with flat faces, have the straw come off a corner and that straw being the lowest point.

When the silicone is cured, use a knife to cut through at the widest. If you need to worry about alignment, you can cut in a wide shallow V. This cut lets you unmold.

It’s not necessary but helpful to leave some gap at the top to fill with, the water will find its way in,

The way that this works is simple. The insulation on the cup causes it to freeze from the top down. The clouding stuff in ice is caused by impurities coming out of solution. As it freezes top-down, the impurities are pushed out of the top chamber and into the bottom still-liquid chamber.

Leave the lid off for freezing. Then to finish, all you really need to do is cut the bits of drain and fill holes, temper the ice, which makes it nice and shiny (and, huh, wet…)

Whiskey snobs will be impressed. You can get best results with distilled water (the bottled jugs at the grocery store are cheap,) but some air will still be trapped and cause problems.