Extreme High Gravity Beer Brewing Part 1

This week I take a look at the brewing of very high gravity beers to include styles like Barley Wines and extreme Imperial Stouts. These beers require somewhat special handling as it can be hard to achieve the very high starting gravity and a good fermentation, and in addition they often require extensive aging.

Very High Gravity Beers

I’ve previously covered high gravity brewing in both articles and podcasts. A few notable ones include my articles How to Brew Big, High Gravity Brewing with BeerSmith and my interview with Michael Tonsmeire on very high gravity barrel aged stouts. These covered many of the basic techniques for brewing higher gravity beers, which is generally considered beers that are 1.080 starting gravity and up.

Today I’m going to go into what I might call extreme high gravity beer brewing, which starts at 1.100 and often can go much higher. This primarily encompasses two styles: Barley Wine and Imperial Stouts, though a few other styles fall into this range like Eisbock or Sahti.

The flavor challenge all extreme high gravity beers face is maintaining some balance in the beer. Due to the extreme starting gravities, these beers usually also have a high finishing gravity. This means they will have a lot of malty sweetness that needs to be offset by something else. In the case of Eisbock and Imperial Stout we’re relying on tannins from the dark malts, sometimes combined with tannins from wood aging to offset the sweetness. For the Finnish Sahti style, rye and juniper along with a strong banana-clove flavor provides balance. English Barleywine is the odd man out as it embraces a rich malty finish and compliments it with a generous dose of caramel malts.

Brewing Very High Gravity Beers

When we discuss very high gravity beers the first challenge is how to achieve the extreme starting gravity. With some extreme imperial barrel aged stouts starting in the 1.160 OG range, you can’t use a traditional mash on these beers. There is simply not enough space in a standard mash tun and even if there was you would get such poor mash efficiency (due to the low total water/grain ratio) that it would be hopeless.

So we are left with a few options to achieve extreme beer gravities:

• An Extremely Long Boil – Many commercial brewers use two or more separate mashes at merely “high” gravities and then boil them down over a long period of time, often 24 hours or more to achieve their high target gravity. Sometimes the second mash is done while the first one is boiling, with the total wort boiled down even further.
• Malt Extract or Sugar Additions – Both commercial and home brewers can brew a moderately high gravity wort and then directly add malt extract or various sugars to boost the original gravity higher before boiling and fermenting. This is probably the easiest way for a home brewer to achieve very high gravities.
• The Eisbock Method – Eisbock is made not from an extremely high starting gravity but actually by freezing the finished beer and removing the ice that forms, leaving a higher alcohol beer behind. Water freezes at 32 F (0 C) while alcohol has a freezing point of -173 F (-114 C) so chilling separates the two. The process, called “freeze distillation”, is illegal commercially in the US without a distillers license, and some care must be taken as you are also concentrating fusel alcohols like methanol which can be toxic at high concentration.

Overall the malt extract/sugar method is probably the easiest for a home brewer. Simply start with as much grain as you can fit in your mash tun and then add either malt extract (liquid or dry) or sugars as needed to achieve your finishing gravity. Be aware that sugars ferment at a higher rate, so you may get more attenuation during fermentation and a lower finishing gravity if you use sugar.

Next week in Part 2 I will look at some of the fermentation considerations that come into play with very high gravity beers. In particular, you need to ensure a good starting environment and good yeast health or you will end up with a stuck fermentation and very high final gravity leaving a beer that is sickly sweet.

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