Step 7: The Boil
Once the wort starts to boil, a countdown begins. Depending on the recipe, you will be boiling the wort for 60, 75, or 90 minutes, we boiled ours for 60 minutes. Immediately after it boils, it's time for the bittering addition of hops, put them in a hop sock and drop it in.
The hops added this early will have their oils mostly broken down by the end of the boil. This will destroy their aromatic properties, but create the bitter flavors that counterbalance the naturally sweet beer flavor.
At fifteen minutes from the end of the boil, the next hop sock is added. This addition is for hop flavor, rather than bitterness. The oils and flavor characteristics of the hops will have time to be extracted from the flowers, but only partially be broken down, adding the hoppy flavor to the beer.
The final hop addition happens just five minutes from the end of the boil. The hop oils won't be broken down at all, and add only aroma to the beer.
Besides adding the various hops characteristics to the beer, the boil also serves to evaporate a number of unpleasant chemicals from the wort, such as dimethyl sulfide. Dimethyl sulfide, or DMS, rather unpleasantly adds a burnt plastic taste to beer.
At sixty minutes of boiling, it's time to remove the brewing pot and start chilling it--this is known as the "Cold break".