Lagering - Chapter 2: How to Lager

Making a Great Traditional Lager

Now that we've cleared up what a lager really is, let's get down to actually making one in a traditional style. It's a little more involved than making a typical ale, but it's well worth it. You're always going to follow the same set of basic steps:

• Build a yeast starter
• Pitch your yeast
• Primary (cool) fermentation
• Diacetyl rest
• Secondary (cold) fermentation
• Serve and enjoy!

Step 1: Building A Yeast Starter

To brew a traditional lager successfully, you really want to make sure and give your yeast culture a running start. This is a pretty straightforward process that will help any beer you make, but it's especially important when you're going to be fermenting at cooler temperatures. For one thing, it's the best way to make sure that you're actually using a batch of live, healthy yeast. Unlike an ale, where it's pretty obvious pretty quickly when your yeast get to work, that's not as easy to see with a lager. Even more importantly, though, starting with a large batch of active yeast going to cut down dramatically on the time that it takes create a sterile, productive environment in your fermenter.

Step 2: Pitching Your Yeast

You'll brew the wort for your lager beer just as you would for any traditional ale. When the time comes to pitch your yeast, you'll definitely want to make sure that your wort has cooled to 60F - 65F first.

Step 3: Primary (Cool) Fermentation

Your fermentation should obviously take place at the recommended temperature for the yeast that you've selected — usually around 50F - 55F, but depending on the strain, this could be as low as 45F. Once cooled, you obviously want this temperature to remain as consistent as possible, especially making sure that the temp doesn't rise above the recommended range while the primary fermentation is underway.

Step 4: Diacetyl Rest

Once the primary fermentation is complete (usually after 2 weeks), then you actually do want to raise the temperature of your batch, again. This temporary warming phase is usually called the "diacetyl rest", and it does a few different things to help your beer:

• It helps to make sure that the primary fermentation process is thoroughly completed.
• It will drive off excess CO2 that was generated through fermentation, and which could generate off-flavors.
• Most importantly, it allows the yeast to absorb a compound called diacetyl, which is generated as a side product of fermentation. Diacetyl creates a buttery, slick taste — it's actually the chemical that's used as butter flavoring for popcorn — and you almost certainly don't want it in your beer. While yeasts will create diacetyl while fermenting at any temperature, warm or cold, they only re-metabolize it at warmer temperatures, so while you don't need to worry about it when making an ale, it's something you need to manage in a lager.

For an optimal diacetyl rest, you want to keep your beer as close to 62F as possible, for 2-3 days. This will allow the benefits of the rest to kick in, without letting the yeast get too warm, and start generating esters and other bad things. Check out our fermentation temperature control tools.

Step 5: Secondary (Cold) Fermentation

Now it's time for the true lagering takes place — an extended period of cold storage, that will condition and clarify your beer. Rack your beer into a carboy, and cool it very gradually, about 5 degrees a day, down to a very low temperature.

At this point, obviously, you want to monitor your temperature closely, to make sure your batch doesn't freeze, but the colder you can keep it (and the longer you can keep it there), the more of the benefits you're going to get.

How Cold is Cold Enough for Lagering?

You can (and should) store your beer at a much cooler temperature for this second phase, than you even did for the primary fermentation...ideally, 35F (or lower)!! If you can't easily lager your beer at a temperature that's close to freezing, there's a very simple rule to keep in mind:

You want to lager your beer at least 5F colder than your target serving temperature

Why? The answer is simple — if you bring the temperature down when you serve it, then you're actually forcing another cycle of precipitation to take place. After the time and effort of lagering, you're still creating the possibility of a chill haze in your beer. On the other hand, if you're bringing the temperature up slightly to serve it, then not only have you clarified your beer as much as possible, but it will actually be able to re-absorb a small amount, and you'll have crystal clear beer.