If you're trying to chill Champagne super-fast, or building an ice bath for a long party, salt is the secret weapon. Depending on the size of the bucket or tub, Add a cup of salt (I use Kosher) for every gallon of water. Make a slurry in the bowl first, whisking the salt with warm water to dilute it. Then dump the ice on top and add cold water quickly. What's the difference between this and the proper bath above? When ice melts in water, it stays at 32°F until it melts away (and gets warmer). When ice meets salt, it melts so quickly at first it uses its own thermal energy to turn into water, but that water chills down much, much colder to, say, around 15°F.
