A fast temperature drop is critical for several reasons:
- Risk of contamination: There are plenty of airborne yeasts and bacteria that would love to feast on your freshly boiled wort when it’s in the range of 80-160°F (27-71°C). You want to be in this zone as briefly as possible.
- Protein coagulation: A rapid cool-down knocks proteins out of suspension and results in clearer beer in your glass.
- More predictable hops utilization: Hops continue to contribute bitterness even at sub-boiling temperatures. Letting wort remain too hot for too long extracts additional bitterness you may not want.
The most popular ways to chill wort are ice baths and wort chillers. And of the latter, you have a few choices, all of them excellent.
Most of us start out using an ice bath, and it’s not a bad choice if you’re cooling down only three gallons or so for a small batch or concentrated boil. Simply fill a kitchen sink or bathtub with cold water, dump in as much ice as possible, and add the pot of hot wort.
Pros: This is a tried and true method that’s simple and effective, provided you wait long enough. And you don’t need any special equipment, just a lot of ice.
Cons: You need a lot of ice. And it can take half an hour or more, making it impractical for full 5-gallon batches and more or less unheard of for larger volumes.
An immersion chiller is nothing more than a coil of copper or stainless steel tubing that you dunk into the boil kettle with 10-15 minutes left to go. Cold water goes in one end, gets heated by the wort as it spirals through the tube, and comes out hot on the other side.
Pros: Immersion chillers are easy to sanitize, readily available, and affordable. There are no moving parts, and they’re virtually foolproof.
Cons: These chillers work more quickly than an ice bath, but it still takes 10-20 minutes, depending on the temperature of your water. And you’ll use a fair amount of water in the process, especially in the summer months when supplies are warm.
A counterflow chiller is a tube within a tube. Hot wort travels through the inner tube, while cold water flows in the opposite direction through the space between the two tubes.
Pros: You’ll chill five gallons of wort to pitching temperatures in 10 minutes or less, and you’ll use a lot less water than you would with an immersion chiller.
Cons: You need a pump or a healthy gravity drop to move wort, and that wort needs to be clean and clear (no whole cone hops detritus) to keep from clogging the inner tube. These are also harder to clean and keep sanitary than immersion chillers. And you’ll pay for it.
A plate chiller works on the same principles as a counterflow chiller, but instead of concentric tubes, wort runs over steel plates that contain cold water. More surface area means faster cooling.
Pros: Plate chillers are by far the fastest way to chill wort. It’s possible to bring 10 gallons down to 65°F (18°C) in five minutes with one of these babies.
Cons: You’ll need to pay extra careful attention to wort clarity so as not to clog the lines. A good gravity flow or pump is needed to move wort, and sanitation requires special attention. And as with counterflow chillers, you’ll pay for the pleasure.
Finally, if you live in a cold climate, avoid the temptation to place a hot pot of wort in a snowbank and walk away. The heat merely creates a layer of ice around the kettle, which traps air and actually insulates the kettle. If you really want to use snow to your advantage, throw a few handfuls into your cooling water.