We should probably start out by talking about how beer becomes beer. It's all about fermentation. Fermentation is the process by which yeast metabolizes the sugars (in beer) into:
1. Carbon Dioxide
2. Ethyl Alcohol and...
3. A whole host of other things that contribute to the flavor, both bad and good.
That's really it in a nutshell. The rest is just mechanics. They are some stunningly complex mechanics, but mechanics nonetheless.
Fermentation is actually a very complex process. The actual scientific study of fermentation is called zymurgy. Zymurgy is defined as the branch of applied chemistry dealing with fermentation, as in winemaking, brewing, the preparation of yeast, etc. For further reading into the complexities of zymurgy click here.
It's good information, but just knowing a few basics about how yeast behave is adequate for the everyday Joe Sixpack Homebrewer (like me) to produce fine brews. In the yeast section of this site, I will attempt to make the subject understandable, yet not oversimplify it.
So give me a good overview of the mechanics already? OK, fair enough. Let's start with a brief description of the most abundant ingredient in beer (aside from water): malt.
Malt is basically the sugars that come from barley (or wheat). The grain is allowed to just begin germination, then stopped. That results in malted barley (or wheat) that would then have to be converted to fermentable sugars via mashing. For the casual homebrewer though, the simpler way is to purchase malt extract (in powder or syrup form) that you can add directly to water for boiling.
Any fermentable concoction that will be turned into beer should be boiled. This boiling concoction of malt sugars, hops, and water is known as wort. It's generally accepted that a wort should be boiled for an hour, with hops added at various stages in the boil to achieve different goals. Hops added in towards the front end of the boil are there for bittering, while those at the back end are there for flavor/aroma. Hops are the flowering tops of the hop vine.
Once the wort has been boiled for an hour, it's cooled and transferred to a container for fermentation. The typical volume of wort for the homebrewer is 5 gallons, so I like to use a 6.5 gallon glass carboy for my initial fermentation to allow headroom.
So now you have a carboy full of potential beer. What's next? Add yeast to it. That starts the process of turning potential beer into real beer. I don't know about you, but I'd much rather drink real beer than potential beer.
Normally, after about 3-4 days of vigorous fermentation in the first carboy (primary fermentation), it's good to transfer the fermenting wort into a secondary carboy to allow the yeast to settle and fermentation to complete. You can leave it in the primary for the entire fermentation if you want to keep it simple. For the beginning homebrewer, this is probably the way to go. If you do go the two-stage route, I've heard different rules of thumb about how long it should stay in the secondary, but the only way to know for certain is to take a gravity measurement of the wort. I usually just kind of go by feel and observation of the wort in deciding when it's done. After a while, you'll develop such a feel. For me, the time period is usually from ~10 days to 2 weeks from the time I started.
Assuming the wort is finished fermenting, it will next have to be transferred to some type of vessel from which you can consume it. I've kegged mine (and artifically carbonated) a few times and had pretty good success, but I generally bottle it. When you bottle, you'll have to add priming sugar (corn sugar) at a rate of 3/4 cup to 5 gallons beer to carbonate it. The corn sugar gives the remaining yeast a bit of food to consume in the bottle and turn into carbon dioxide, which is what gives beer the characteristic "fizz". After adding this priming sugar, it will take another ~10 days to 2 weeks in the bottle before carbonation is complete. You can then refrigerate and enjoy.
The one thing I haven't explicitly stated in any of the above is that sanitation is key to a good product. In every process, things must be kept clean or you may not like the taste that results.
Thanks for reading and good luck in your brewing.
- Mike