Boiling the wort accomplishes several vital tasks and is another key step in producing a quality beer.  Boiling wort doesn’t require any particular skill and is a great time to socialize and drink homebrew, just make sure you watch for boil overs! 

Why Boil: 

Most homebrew recipes call for the wort to be boiled for at least 60 minutes and some call for boils of 90 minutes or longer.  While at first these boil times may seem arbitrary but they aren’t.  One of the most important things accomplished by the boil is the pasteurization of the wort.  Keeping up a steady boil for 60 minutes (or more) is a sure fire way to kill any bacteria or other microorganisms that may harm your beer.  By killing off most of the microorganisms you are making the job much easier for the yeast you will be adding later on. 

Boiling the wort also helps coagulate the proteins in the wort.  As you boil you will probably notice foam rising to the surface.  This is the proteins in the wort clumping together.  Eventually the protein clumps become heavy enough that they break up and sink back into the wort and are now called hot break.  By the proteins coagulating and falling out of suspension, you can leave most of them behind in the brew kettle which can potentially help in having a clearer, less hazy final product. 

It is also during the boil that the hops are added.  The hops add bitterness, flavor and aroma to the brew and play a major role in many styles of ales and lagers.  Additionally, hops can also act as a natural preservative when added to beer.  Only through an extended and vigorous boil can the bitterness (remember, wort is very sweet so bitterness here is a good thing!) of the hops be released. 

Procedure:

Put brew kettle on heat.  Bring wort to a boil.  Congratulations, you are done! 

Well, OK, maybe there is a little more to it than that, but fundamentally boiling wort is no different than boiling water.  If you produced your wort using either the extract or partial mash method you are more than likely not going to boil more than 3 gallons or so of wort.  Most kitchen stoves have a burner large enough to bring this volume of wort to a boil in a reasonable amount of time.  If you produced your wort with the all-grain method (or went big with one of the other two methods) you should have at least 6 gallons of wort to boil.  You may be lucky and have a kitchen burner big enough to boil 6 gallons of wort, but here at the Homebrew Garage we brew in the garage for a reason!  We boil our wort over a propane burner (like the kind used to fry turkeys) that is more than adequate to boil the full volume of wort. 

Once you have your brew kettle filled with wort and over the heat you want to bring it to a boil.  It is a good idea to stir frequently (especially if you used malt extract) to encourage even heating and to prevent anything from scorching on the bottom of the brew kettle.  As the wort comes to a boil you want to watch for the foaming prior to the hot break and stir constantly to prevent the wort from boiling over.  If it looks like a boil over is eminent remove the brew kettle from the heat until the danger has passed.  If you have 6 gallons of work in the pot be very careful as it will be heavy and you don’t want to spill boiling hot wort on yourself or on any helpers.  Once the hot break has happened you are more than likely out of the woods as far as boil overs are concerned.  Remember to keep stirring regularly for the duration of the boil. 

As mentioned above hops are added to the wort during the boil.  Hops come in several different forms (pellets, plugs and whole leaf are most common) and numerous varieties.  Each variety of hops varies in flavor, aroma and bittering ability.  Hops are generally selected for brews based on their characteristics and are added at different intervals during the boil. 

Bittering hops are added near the beginning of the boil so that they have a longer time to release the alpha acid resins that add the desired bitterness.  Because bittering hops are generally boiled for at least 60 minutes most of the flavor and aroma is boiled away leaving only the bitterness behind. 

Flavoring hops are added later in the boil (usually with around 30 minutes remaining) and due to the shorter time in the boiling wort don’t add as much to the bitterness as the bittering hops.  The shorter boil also keeps more of the flavor and aroma of the flavoring hops in the wort. 

Finishing hops are usually added to the boil in the last 15 minutes (sometimes at the very end) and add almost nothing in the way of bitterness to the brew.  Finishing hops are essentially just steeping and add plenty of flavor and aroma to the finished product since little of those properties are boiled away. 

Make sure to stir vigorously while adding hops as they can cause foam to develop quickly which could result in a boil over.  Follow the directions with your recipe for when and in what amount to add the hops to the wort. 

OK, now you can congratulate yourself for successfully completing the next step to a great tasting beer!