* 1 small cooler
* freezing winter nights
* tap water
The Weather Channel explained this.
You don't freeze the whole thing, just a top layer.
Pros: Perfectly clear ice. Total win. Simple instructions. Inexpensive. Large mass of ice at once. Impurities pushed out. No filling ice trays.
Cons: Hassle. Jacked by Global Climate Change™and el Niño and ordinary weather disruptions. Wet mess. Must be thawed to release and refrozen causing problems. Must be chipped to fit glasses. Out of doors airborne debris. Knife hazard.
