Brewing High Gravity Beer: 5 Tips for Producing High Levels of Alcohol & Keeping the Yeast Healthy
Beer gravity refers to how much sugar is present in the wort before the yeast is added and any fermentation begins. This is known as “original gravity (OG)” and is measured at the very beginning of the gravity brewing process before anything has really started happening yet.
Generally, the higher the OG, the higher the sugar content and the higher the alcohol content in the beer will be at the final gravity stage. The yeast consumes the sugars and ferments the wort, which creates the beer. It’s easy to see how there’s a direct relationship.
As most hobbyist brewers quickly learn in order to create your own mini brewery, when brewing high-gravity beer with a high ABV and the taste of a ‘big beer’ like a Russian imperial stout, a pale ale or other strong beer, you’ll need a hydrometer to measure the OG and to take additional specific gravity measurements throughout the brewing process. For reference, the specific gravity of water is 1.000. Anything higher than that is denser than water. High density beers are defined as having OGs greater than 1.065.
Obviously, you’ll need a number of ingredients to make your favorite beer, which could include fermentable sugar, malt and malt extract, dry yeast and yeast starter and yeast strain, mash tun, different grains, and many other ingredients.
Here are some great tips on how to produce strong beer with high alcohol content and keep the yeast healthy:
1. Watch Osmotic Pressure
If you don’t recall osmotic pressure from chemistry class, here’s a quick recap. If there are solutes of two different concentration on either side of the semi-permeable membrane, the solute will cross the membrane until the concentrations on either side are equal. The force exerted on the membrane as this is occurring is the osmotic pressure. In brewing, the membrane is the cell wall of the yeast.
In high gravity worts, the concentration of sugar outside of the yeast will be much high than inside, which means the osmotic pressure will be high. This can damage the yeast and change its metabolism which will affect the fermentation of the beer.
Aim for an OG of 1.106, which is 1.106 times the density of water. If you add more throughout the fermentation process, make sure to also add nutrients for the yeast so it will stay healthy and be able to function properly.
2. Use the Right Yeast
Choose a yeast that’s going to be able to tolerate the high sugar and alcohol concentration. You want one that is highly attenuative, which means it will actually ferment a lot of the wort sugars. Highly attenuative yeasts will be able to ferment at least 78% of the sugars.
This is an important part of home brewing because it affects the taste of the beer. Whatever sugars the yeast does not ferment will remain and add sweetness to the final product.You also want to make sure the yeast you choose has a high enough alcohol tolerance to survive the brew you’re making. Once a strain of yeast reaches a point where it can no longer tolerate the amount of alcohol in a brew, it will just stop working.
3. Oxygenation and Aeration
While some people think too much oxygen isn’t good for the taste of the beer, oxygen and aeration need to be considered carefully with high density beers. The yeast is working really hard and it needs oxygen to reproduce.
As the specific gravity increases, oxygen solubility gets harder and harder. For high gravity beers, though, you need more oxygen for the health of the yeast so you need to add more, but you need to add it slowly.
4. Aim for a Low Fermentation Temperature
Try to start with a fermentation temperature of about 65 degrees F and monitor it throughout the process. Fermentation releases heat which will raise the temperature. Because there is a lot of sugar in high-density beer and a lot of fermentation going on, it’s better to start low than to struggle to keep the brew cold as the process continues.
There are a lot of ideas about how to keep the temperature down. There are some really simple, inexpensive methods you can use:
- Use the “wet tee shirt” method, aka evaporative cooling. Put the fermenter in a few inches of water and place a wet tee-shirt over the fermenter. Make sure the bottom of the shirt sits in the water. Blow a fan on it to encourage evaporation. While this method can lower the temperature by 10-15 degrees, it’s also not very exact and won’t be able to hold temperatures consistently.
- Put your fermenter in an ice bath so that it’s submerged up to the level of the beer. Make sure you use a container tall enough to that the fermenter can actually be contained inside. It’s better to use frozen bottles of water as these will melt more slowing. The water is contained and so it won’t melt quite as quickly which will help keep the temperature down longer.
- In the winter, keep the fermenter in the garage or basement. Take advantage of the natural cooler temperatures.
- Build a refrigerator by enclosing the fermenter in a container like a large box. Cut a hole in the side and create a shelf out of something waterproof. The idea is to place a large amount of ice on the shelf.
- Buy a refrigerator dedicated to fermenting. You can easily find a good, inexpensive one at a scratch and dent appliance place.
5. Be Patient
There are a lot of things that can go wrong during any brewing process and high gravity beer brewing is no exception. There are a lot of things that might not work out right and you may need to start all over again. Put simply, in order to create your personal brewing company, you need to be patient!
Sometimes, with high density beers, they might not taste good right away—or even after a few months. Sometimes, you do have to wait for the reward.
Brewing beer is an art form and making a proper high density beer is no easy task. There are a lot of different factors you have to look out for in order to make sure your brew turns out the way you expect it. Sometimes, it will take you a few tries to figure out. By following these tips, you should get a pretty basic idea of what you need to do to continue building your brew.