Brewing Considerations for Very High Gravity Beers

Brewing high gravity beers like barley wines, tripels, and imperial stouts present some challenges unique to high gravity brewing. This week I provide a few tips and considerations that come into play when brewing high gravity beers.

Big Beer Challenges

High gravity beers which start at around 1.080 original gravity and can go as high as 1.120 present serious challenges that may surprise the average homebrewer. You need to consider the fact that you may get much lower mash and brewhouse efficiency, may overflow your mash tun with the grains needed, and also need to take several factors into effect when selecting yeast. I’ll cover the major items below.

Mash Considerations for Large Beers

First, you need to understand that you will almost certainly get lower mash and brewhouse efficiency for a high gravity beer than you would get from your system for an average beer. The reason for this is quite simple. You will be using a lot less water per unit of grain when mashing and sparging. Consider a typical 5 gallon (19 l) batch where you may have 10 lbs (4 kg) of grain. To make this beer you are running about 11-12 gal (23-27 l) of water through the grain bed between the mash and sparge or a bit over 1 gal of water per lb of grain.

A high gravity beer may have 15 lbs (6 kg) of grain for the same 5 gal (19 l) batch which means only about 0.73 gal of water for a pound of grain. As a result fewer sugars will be extracted per pound of grain, and you will get lower brewhouse and mash efficiency. So when you brew a large beer you probably need to lower your brewhouse efficiency by 10% or more to compensate for this.

A second item to consider is how much grain and water you can fit into your mash tun. A 5 gal (19 l) Gott style cooler, for instance, will only hold about 13 lbs (5.9 kg) of grain, which is not enough for a very high gravity beer. I highly recommend you calculate the space needed for grain and water (BeerSmith does this on the mash tab) so you know if your mash tun is large enough. If its not you may need to either split your mash into two vessels or add malt extract during the boil to raise the gravity up to your target.

Yeast Considerations for High Gravity Beers

I made a series of very high gravity meads this year, some starting as high as 1.160, and I learned a tremendous amount about high gravity fermentation.

High gravity worts can put significant stresses on your yeast. When selecting a yeast, for example, you need to consider the alcohol tolerance level of the yeast strain. Many typical beer yeasts have tolerance levels only in the 8-10% range, which means they will stop fermenting if the alcohol level gets higher than 8-10%. If you are brewing a 14% alcohol barley wine with regular beer yeast it will stop fermenting around 10%, and you’ll end up with a very high finishing gravity and a very sweet barley wine. Make sure you select a yeast strain that can tolerate the alcohol level you are targeting, and use wine or champagne yeast if brewing a very high gravity beer.

Another consideration for very high gravity beers is called osmotic shock. This is primarily an issue for dry yeast, though most of the high alcohol wine and champagne yeasts used in high gravity beers come in a dry form. The basic problem is that dry yeast cells are not able to properly regulate their cell wall until they have been hydrated. Also high gravity yeasts have a very high sugar concentration. So if you add dry yeast directly to a high gravity wort or must, the osmotic pressure from the sugar can breach the cell wall membrane before the yeast cell wall is in a state to regulate its flow, resulting in a high fatality rate. While its unlikely to kill all your yeast in a beer, it can result in a less than optimal pitch rate.

To avoid osmotic shock with dry yeast it is important that you properly hydrate the yeast before adding it to your wort. The method I recommend is to add lukewarm water at about 104 F to some GoFerm first. When the GoFerm is mixed in then add your yeast and allow the mixture to sit. Slowly add small amounts of wort until the mixture is down to within 10 degrees (5 C) of your wort temperature. You want to take time when doing this as you don’t want to alter the temperature of the mixture more than about 10 degrees in 10 minutes to avoid shocking the yeast. The combination of hydrating the yeast and slowly adding some wort will minimize the effects of osmotic shock and give you a healthy fermentation going forward.

Fermentation and Aging Considerations

Not surprisingly, big beers take longer to ferment out and age. Most big beers take several months, and some like barley wine can take a year or more. Though fermentation may be extremely rapid at first, often it will slow to a crawl as the alcohol level rises and the beer nears completion. As a result, patience is needed when fermenting a big beer. I generally allow extra time both for the primary and secondary fermentation and, even then, give it a bit more time before I consider bottling a big beer.

Even after fermentation is complete, it can take some time for the higher alcohols (fusels), yeast and other flavors to age and mellow out. Some beers like barley wines and big braggots take a year or more to reach peak flavor.

Hopefully these tips will help you as you plan your next high gravity beer. Thanks for joining me on the BeerSmith Home Brewing Blog. Be sure to sign up for my newsletter or my podcast (also on itunes…and youtube…and streaming radio station) for more great tips on homebrewing. Also check out the How to Brew Video series I shot with John Palmer if you want to learn more about all grain brewing.