With all of my recent lager recipes I've put up on this blog, I got to thinking about actually posting some tips on the whole process. If you read basic information on lagers vs. ales, you get the usual "bottom-fermenting vs. top-fermenting; cold vs. warm fermentation; clean vs. fruity flavors", etc. How to translate this to home-brewing, however, can get a bit overwhelming and confusing. Well, it did for me anyway!
Here are a few major topics in homebrewing lagers compared to ales:
Equipment - Most of your typical ale-brewday will be the same when brewing a lager. You do your mash, vorlauf, sparge, typical boil, wort-cooling, etc. It's when you get to the yeast and fermentation that things change and get trickier. Equipment-wise, you really just have to decide if you want to buy a fermentation chamber, which typically means a fridge or freezer bypassed by a temperature controller. This is quite essential for lager-brewing in general, especially during warmer months, and is really great to have for any brewing at all, as it allows pretty much complete temperature control by the user. If you have a cool area of the house to set a fermenter, you can do this as well, but there's no guarantee this way that you'll get the temps that you want. Sometimes temps will get too warm for brewing a proper lager, and other times they'll get too low. I once brewed a California Common (an ale-lager hybrid) during early spring, and set the fermenter in the garage to get temps close to 60 F. Unfortunately, the temperature dropped at night, the yeast flocced out, and I couldn't wake them up again, resulting in a stuck fermentation and one overly-sweet and low-ABV beer. You can also try to control temperatures using the water-bath/wet shirt/electric fan trick; I've talked to some who have had pretty good results with this approach, but it obviously involves a lot more attention. It'll really come down to what's affordable, what you have room for, etc.
Temperatures - Obviously the biggest difference in brewing lagers vs. ales. While ale fermentation temperatures can range anywhere from low-60s F to high 80s (depending on the style, of course), all lagers are typically fermented at somewhere between 48-55 F. CAN lager yeast actually ferment at ale temperatures? They sure can, but you're going to get a lot of fruity-ester development, and that's not usually a feature in aroma or flavor that you want to see in a lager. The lower temperatures allow the lager yeast to ferment clean, so that there's very little (if any) additional esters or phenols produced.
Fermentation speed - Because of these lower fermentation temperatures, primary fermentation will take longer in lagers than it does in ales. While a lot of ale styles can finish primary fermentation in as little as several days, lagers can take a week or longer, easily. Primary fermentation also typically takes longer to begin with lagers, depending on your approach; don't pitch yeast into a lager style and expect to see fermentation begin within hours. It can often take a good 24-48 hours before any visible signs are seen (e.g. airlock bubbling). You still generally see a krausen during fermentation, but it's usually not as large as what you can see for an ale, and fermentation itself doesn't appear to be as "violent" - the chances of having a blow-off while fermenting a lager are probably pretty low in your typical 6 - 6.5 gallon fermenter! You DO still want the ferementation to be quite active, however, as it increases the amount of sulfur that is blown off.
Amount of yeast needed - You really need to pitch twice as much yeast for lagers compared to ales. This is very important, and often ignored. It's also one of the major pains with brewing lagers - unless you want to buy several packs of yeast to pitch (and who can afford that?), you have to plan well ahead and build up a good yeast starter. For comparison, a 1.050 gravity ale would require a 1 L starter with intermittent shaking (if you follow the pitching calculator at mrmalty.com - and you should!). With a similar-gravity lager, on the other hand, you would need to make a 4.5 L starter to get the recommended amount of yeast! Crazy, isn't it? I wouldn't even recommend making a first-lager bigger than that; if you were hell-bent on brewing a high-gravity lager like a Doppelbock, I'd suggest brewing a smaller lager with the same yeast, and then culturing the yeast cake to use for the Doppelbock. Otherwise you'll be spending a lot of money and time on building super-sized yeast starters.
To secondary or not to secondary - If you've done your research on brewing ales, you probably know by now that racking to a secondary fermenter just isn't necessary - unless you're dry-hopping, adding secondary ingredients, or aging the beer. In lagers, however, moving over to secondary is a must-do, simply because the actual "lagering" process (where you drop the temperature of the beer down to near-freezing) takes time - more time than the beer should be sitting on the yeast cake from primary fermentation. Depending on the beer, lagering can take anywhere from several weeks to many months, so it really has to be in secondary for this final step.
Results - So, aside from the yeast, process, etc. what is the difference b/w a lager and an ale as an end-product? Of course there's lots of lager-styles, and even more ale-styles, but I'd mainly say that lagers are typically CLEANER than ales. Of course there's exceptions to this rule, just like all the others in brewing, but it's generally true. Fruity esters and spicy phenolics, which are so often expected and welcome in many styles of ale, are considered flaws in lager beers. The slow, clean fermentation, and long lagering process should result in a beer where the malt and hops are allowed to really shine. As a result, other possible brewing flaws related to water, oxidation, stale ingredients, etc. are more easily noticed. This is another reason why lagers are more difficult to brew properly than ales - it's that much easier to pick out problems.
My approach to brewing lagers... your results (and opinions!) may vary...
I tried to do a fair amount of reading on this subject before I brewed my first lager. There's a lot of information out there, some of it conflicting (of course). The following procedure has worked well for me; I have a deep freezer with a digital temp-controller, which technically would be needed to follow this approach. But if you want to try using the trick with the water-bath mentioned above, you can certainly give that a shot and just add more ice when you want to gradually decrease the temperature.
There are two basic approaches to beginning lager fermentation. An older, more classic method is to pitch the yeast "warm" (say, mid 60s F) and wait for visible signs of fermentation to appear. When they do, you bring the temperature down to 50 F or so, and continue until fermentation is complete.
The newer approach, the Narziss method, is to pitch the yeast at around 45 F, a little lower than what you want the fermentation temperature to be. A lot of experts seem to agree this is the way to go. Why? It's argued that when you pitch at ale temps, and fermentation begins, the yeast will have increased diacetyl production. Also, if you then lower the temperature too quickly, the yeast may floc out and/or produce unwelcome byproducts. Just because they're lager yeast doesn't mean they like to go from 68 F to 50 F overnight... too-fast temperature drops are not healthy for ANY type of yeast. The Narziss method will result in slower fermentation, but less diacetyl and other byproducts should be produced. This is the method I've used each time.
When primary fermentation begins to visibly slow, it's usually time for a diacetyl rest. Even though less diacetyl should be produced, in theory, by pitching cold, it's still a good idea to do a rest (especially depending on the yeast - some are more well-known diacetyl producers than others). If you want to be sure exactly when you should begin this rest, you can take a gravity reading of your beer - when it's within 4-8 points of your target FG, that's a good time. I usually just take the fermenter out of the chamber and set it somewhere at room temperature. Once the temp on the fermometer reads anywhere over 60 F, I leave it for a couple of days to let the yeast clean up any residual diacetyl that may be around.
So, now what? At this point I lower the temp back to where it was before the diacetyl rest. But I try not to just drop it back in the freezer with the temp set at 50 F... that could be a quick drop of almost 20 degrees over a short period. Maybe I coddle my yeast too much, but I've had too many quick-drop temp issues at this point! So, while the beer was undergoing its diacetyl rest, I increase the temp of the chamber to a few degrees under what the beer is currently resting at. So, if the fermometer reads 65 F, I'd bring the chamber to about 62 F, and begin the temp drop there. I'll then decrease the temperature by 1-2 F every 12 hours or so, until it's back down to 50 F.
This is where I'll leave the beer until it's been about 3 weeks since pitching the yeast. Now it's time to rack to secondary to begin lagering. Once the beer is in the secondary fermenter, I leave it in the chamber and begin a gradual decrease in temperature. This time I go even slower than before; it's generally agreed that about 2 F each day should suffice, so I lower the temp by 1 F every 12 hours (roughly). I'm sure it's fine just to go by 2 F every 24 hours, but since I usually don't have trouble remembering, I go in shorter intervals. Most people lager as low as 32 F (the freezing mark), or a bit above. However, I've read in
"Yeast: The Practical Guide to Beer Fermentation
" that temps lower than 40 F generally don't involve a lot of yeast activity anyway. Not that they're really doing a lot at this stage anyway, but there should be some minor activity where they're doing a bit of further clean-up of the beer. So, I personally shoot for a lagering temp of about 38 F.
So, how long do you really need to lager for? This is definitely a personal preference. While the beer is lagering, the flavors are melding together more, and as more yeast drops out, the beer becomes even clearer. In general, the higher the OG of the beer, the longer it should be lagered. I've seen recommendations of 1 month for every 4 OG points over 1.050, but it's really up to you. Something smaller like an American Lite Lager would probably be fine after 3-4 weeks; a Doppelbock, on the other hand, should probably be given a good 3-6 months before bottling.
Speaking of bottling, when you've had a beer lagering for a while at low temps, it's not a bad idea to add a bit of dry yeast to the bottling bucket along with your priming sugar. I'll rehydrate about 1/5-1/4 pack of ale yeast (it's ok that it's ale yeast, you're just looking for carbonation - no flavor developments or anything), and add it after the beer has been racked on the priming sugar. This is just to make sure that you have enough yeast for carbonation; when a beer has been at cold temps for a long time, a lot of the yeast will be asleep at the bottom and not make it over to the bottling bucket. A lot of times it's probably not necessary, but it's good to be sure. You can then just leave the bottles in a warm room somewhere for a couple of weeks to carbonate, like you'd usually do with ales.
So, that's my method. With six lagers brewed, I'm far from being an expert, and it's not exactly the final word on the subject, but it's worked for me so far. Please don't hesitate to point out errors or make any helpful additions!
For example, using the yeast calculator at mrmalty.com, if you enter that you're going to brew a 1.060 lager, the calculator tells you to make a 7 L starter (with intermittent shaking selected). Crazy, right? Who has a bottle large enough for a yeast starter of that size? Not to mention how expensive that much dry malt extract would be, if you don't happen to have starter wort frozen and on hand. One may immediately assume that if you made two 3.5 L starters, one right after the other, you'd end up with the same amount of yeast, but that isn't the case. It's kind of complicated, but basically the amount of wort you use changes the yeast inoculation rate. A 4 L starter would result in more yeast, for example, than a 2 L starter, but not proportionally-so (e.g. a 2 L starter, with intermittent shaking, would result in ~250 billion yeast cells; a 4 L starter, ~350 billion cells... not the 500 billion you may first assume).
