I've heard that brewing anything over around 14% ABV is pretty much impossible…and that achieving anything over 11% in a homebrew environment is not very realistic. Is this true? If so, how do they make beers like the Samuel Adams Utopias?
14% would be pretty high, even for high gravity yeasts, but 11% is definitely realistic. There are a few tricks to getting high ABV. You want really good aeration so that the yeast are healthy, often this means aerating when pitching and again the day after.
You also may want to add sugar slowly instead of putting it all in at once. This is easy with belgians for instance because you can just start with the malt and then add belgian candi sugar slowly, putting a little bit in every day or so. This is also a good technique for brewing things like mead.
And then just basic things that you want with every beer, but are especially important, like high pitch rates, a large starter, good temperature control, etc.
11% is very realistic though, wine homebrewers do it all the time!
Edit: As to how higher gravity beers are made, it looks like Utopias is actually a true beer, it just is fermented for a really long time using hardy yeast and a lot of simple sugars. A lot of other higher gravity beers (Sink The Bismark, etc) use ice distilling to increase ABV after the beer is brewed.
For very high gravity beers, you can use White Labs Super High Gravity Yeast - WLP099. It has a stated alcohol tolerance of 25%. You can use just this yeast, or use the regular yeast that you want to use to produce the dominant flavor profile, and then pitch WLP099 when fermentation is 2/3 complete (ideally, from an active fermenting starter comprising the same wort as the main beer.)
While you can brew high gravity beers just like regular beers, there are two common faults that occur in a homebrew setting:
- higher alcohols - this gives a solventy aroma and taste to the beer. Caused by yeast stress, such as too few nutrients and by too high a fermentation temperature.
- high finishing gravity - again, this is caused by the yeast dropping out early, due to insufficient nutrients, alcohol intolerance, or temperature swings
Both are reduced to a small degree by time. But the best way is to use the best practices when brewing the high gravity beer:
- Oxygenate with pure oxygen to attain 15ppm of O2. Oxygen solubility in wort decreases with gravity, so airation via shaking etc.. doesn't provide sufficient O2. Oxygenate at 6h, 12h and 18h after pitching to ensure successive generations are able to propagate.
- use Yeast nutrients (ideally a blend containing micro-nutrients as well)
- pitch a big starter - at least 1.5x what you would normally pitch for the given OG. (at least 1.5 mil. cells/ml/°Plato)
- regulate the beer temperature. This is particularly important since the yeast will easily push the beer up 10-15°F above ambient temperature during the first few days of fermentation, causing harsh fusel alcohols to be produced. Keeping the beer temperature low (as low as 15C/60F) will reduce the amount of fusel alcohols produced. As fermentation slows, the temperature is then increased towards 22°C/75°F to ensure the yeast don't drop out before the target FG is reached.
With these processes in place, you can turn around big beers in a couple of months, rather than waiting over a year as traditionally done. The same applies to making mead. I recently brewed a 12% wheatwine that is very enjoyable in just 10 weeks.
I can recommend this page to view the tolerance levels of White Labs different yeast strains.
Look up fractional freezing, Brewdog use this technique with "32% Tactical Nuclear Penguin" and " 41% Sink the Bismarck"