He's Misstra Know It Alt
Tracy Hurst at Metropolitan Brewing has called me both an Alt Savant and a Düsseldork. I'm pretty sure it's not so much a reflection of my knowledge of Altbier as it is my passion for the style. I think most brewers pick a style or two that they really want to perfect. In my case, Düsseldorf-style Altbier is definitely my white whale.
Part of my motivation for pursuing the perfect Altbier is that I fell in love with the style the first time I tried a Diebels Alt as a college student studying abroad (I was sitting in a basement jazz club in Reutlingen, Germany, trying to summon the courage to jump on stage during their jam session, when my buddy Joon--a German-Korean saxophone player from Düsseldorf--bought me a bottle). Part of my motivation is that hardly anybody (with the exception of Metropolitan) brews a Düsseldorf-style Altbier in the U.S., so when I started brewing my only options for drinking an authentic Alt were traveling to Düsseldorf or brewing one myself.
At any rate, I'm far from an expert on the style, though I'll cop to knowing more about Alts than most American brewers. I've had the pleasure of visiting Düsseldorf twice (in 2007 and 2011) and can't wait until I go back again. I want to say the second beer I brewed was an Alt, and since then I've brewed more batches than I can remember... certainly more than any other style. I even had the pleasure of taking a day off of work to help Doug and Tracy at Metro brew their I-Beam Alt, the predecessor to their Iron Works Alt (which you all should go out and buy NOW).
All that being said, my homebrewed Alts have been inconsistent to say the least. I would go from dry and bitter to sweet and not-so-bitter and back again, always having trouble dialing in that perfect combination of maltiness, but with a dry finish, and a crisp bitter hop foundation that isn't TOO bitter. It's hard, especially at the homebrew scale where mash temps, alpha acid percentages and hop utilization can all have large margins of error.
So what have I learned? Well, first and foremost, I'm a big believer that German-style beers should get their maltiness primarily from Pilsner and Munich malts (which give a rich, bready sweetness) rather than crystal malts (which give a sugary sweetness). So I think the first thing you have to nail down is your Munich to Pilsner ratio for your grain bill. You can add a little CaraMunich (and I do add a pound of Caramunich III per ten gallons) but that shouldn't be your primary source of maltiness. (The exception is Uerige, which is all Pilsner plus a small amount of specialty malts, but it's the least traditional of the Altstadt Alts and in my opinion is too thin and thus unbalanced in its bitterness.)
Now an early mistake I made was trying to make my Alt maltier (to stand up to the hop bitterness) by upping the temperature of my saccharification rest. But I quickly learned that upping your mash temp leaves you with a fuller, sweeter maltiness, and an Alt needs a dry finish. As such, I do a protein rest at 122°F and a sacc rest at 151°F. If you want your Alt to be maltier, up the Munich; don't up the mash temp.
The final part of the equation is obviously the hoppiness. Your level of hops will be dependent on both the maltiness of your beer and your personal preference for bitterness. Nearly every American Alt I've had is too low in bitterness* (Metro's Iron Works is to style, though even that is on the low end of the spectrum by Düsseldorf standards). Our last Alt came in at an estimated 45 IBU's with an O.G. of 1051 and it just won first place in its category at the inaugural Chicago Winter Brew Fest, so I guess it strikes a nice balance.
That being said, I had a chance to try my latest Alt side-by-side with a bottle of Füchschen Alt and I've decided I want to cut my Munich down from 14 lbs. to 12 (for the record, I use Best Malz Munich II, which is a dark Munich) and up my Pilsner from 4 to 6 lbs. and then drop the IBU's closer to 40. The idea is to drop the maltiness a little (to make it slightly lighter) and then reduce the bitterness accordingly. Unfortunately there's no easy way to calculate how fewer IBU's I need to compensate for the decreased Munich, so I'm just guessing. But the result should be a slightly lighter but equally-well-balanced Altbier.
So, I guess that concludes my rambling about Alt. Let me stress once again that this isn't authoritative. It's simply what I've learned based on some reading, some tasting, and lots of trial and error. If anybody else has thoughts, I'd love to hear them. Here's to building a better Altbier!
* I should clarify that most Alts from production breweries are under-hopped. I've had several great Alts from American brewpubs, but unfortunately those tend to be one-off brews and are almost always only available on draft.