Brewing Session Beers


At the August 2014 meeting, I presented a brief educational discussion on brewing “Session” beers.  Below is an edited version of the presentation, including the portion in which I described using math to compare the perception of bitterness between two beers.  If you have any questions,please feel free to comment below.

While there aren’t any official style guidelines for session beer from the BJCP, there are some guidelines offered by The Session Beer Project, started by beer writer Lew Bryson as a backlash against the ever-imperial world of beer (Think Double Imperial Russian Stout or Double Trippel, etc.)

Lew and some of his friends decided they preferred “session” beers, and they were seeing fewer and fewer of them in the market, as every brewery seemed bent on brewing higher alcohol beers or beers which were deliberately out of balance.  So, they started the Session Beer Project, which was intended to be a movement against the increasing tendency towards “Extreme” brewing.

They knew what they didn’t want, but then they had to decide what they DID want.

So they came up with a definition of a session beer, and it is this:

► 4.5% alcohol by volume or less

► flavorful enough to be interesting

► balanced enough for multiple pints

► conducive to conversation (beer does’t overpower the conversation)

► reasonably priced

If that seems vague…it is. Here’s another definition: low-alcohol, but not low-taste. It’s subjective. Live with it, and enjoy it. We’re here to help make your night out more fun, more tasty, and more safe. Cheers!

Examples: dry stout (Guinness, O’Reilly’s), porter (Geary’s London Porter, Boulevard Bully Porter). helles (Victory Lager), Belgian pale ale (De Koninck), hefeweizen (Paulaner, Schneider, Penn), most pilsner (Stoudt’s, Pilsner Urquell), brown ale (Newcastle, cream ale, steam beer (Anchor Steam), dunkel (Sly Fox Dunkel, Victory Dark Lager, WarsteinerDark), witbier (Allagash White, Blue Moon Belgian White), kölsch (Cap City Kölsch, Gaffel), and bitter, when you can find it here in America… Not a comprehensive list, but you get the idea.

The 4.5% alcohol was not an arbitrary number, either.  They wanted to make sure they came in below the average beer (Budweiser is 5%, though Bud Light makes the 4.5 cut), and well below most Standard Craft Beers.  Some craft beer drinkers set their bar even lower, requiring the ABV to be under 4%.  The point is that the alcohol is low enough that you can drink more beer and be less intoxicated.

A great session beer should be designed in such a way that you can drink a few and not get palate fatigue, have to call a cab, or be bored by your beer.

It’s a trick to balance a beer well.  Whether you are brewing a hop-heavy Session IPA, biscuity malt-forward bitter or a salty gose, having lighter flavors means the balance is more delicate.  Refining a good session beer recipe can be trickier than using more robust flavor profiles and can take a bit of trial and error.

Practical Advice about Balance: 

Let’s talk about something you can actually use to brew a session beer.  First, keep the alcohol low.  Cut back on your grain bill and use percentages to hit a good ratio of specialty grain to base malt.  Some tweaking may be in order to ensure it retains a full flavor, but be cautious how much you increase the percentage that makes up the specialty grain, as too much of a good thing can be overpowering, and balance is key to developing a good session beer.

You’ll also need to back off of the hops a bit when decreasing your grain bill, but you’ll still need to maintain balance.  This is also tricky unless you have a way to predict the result of tinkering with a grain bill and hop bill.

Some brewing software, such as Beersmith, will do an estimation of the balance, but to give you an idea of how this can be done, here’s some useful information about predicting the balance of a beer.

The IBU number doesn’t mean much to the drinker unless you also know how well that number is balanced against the other flavors in beer.  For this discussion, we’ll limit the “other flavors” to malt flavors, and to quantify those, we’ll use the gravity.

Before we get too far, please understand that this is simplifying the myriad of flavors available in malt and hops and is meant as a guideline for how you can get an IDEA of how well your beer will be balanced.

Ray Daniels and the BU:GU

The ratio we’ll use is the Bitterness Units to Gravity Units.  (BU:GU)  This ratio was first introduced by Ray Daniels in Designing Great Beers.  It measures hop bitterness against malt sweetness where the higher the number, the higher the bitterness is to the sweetness in the beer.  It’s calculated by dividing the IBU by the Original Gravity of the beer.  This is the method most software uses to estimate the balance, and it works as a good estimation most of the time.

For example, if we have a beer that hs 25 IBUs and a 1.050 OG, you would divide 25 by 50 to get .5 (take everything after the decimal in the gravity).  On the BU:GU scale, that would be considered “balanced” and land somewhere in the Irish Red to American Schwarzbier level.  An American Pale Ale would come in around .75 or so, and an American IPA would approach .85-.9.  An Imperial IPA starts climbing towards 1.2 pretty fast.

On the malt-heavy side of things, a weizen would land at about .25, Baltic Porters around .4, and Scotch Ale around .35.

This is the simplest mechanism to predict your results, but if you want to go a step further, you can also take into account the apparent attenuation of the beer.

The Mad Alchemist adds Apparent Attenuation

The Mad Alchemist came up with a formula incorporating the Apparent Attenuation into the BU:GU formula to account for the dryness and increased bitterness perception of a highly attenuated beer.  It uses a constant of .7655 as the average attenuation of all beer styles.  The formula is this:

Relative Bitterness Ratio

RBR = (BU:GU) x (1+(ADF – 0.7655)) where ADF is your apparent Attenuation and the BU:GU is the bitterness to gravity ratio we talked about a minute ago.

Just as in the BU:GU, the higher the number here, the more bitter the beer will seem to the consumer.  Let’s say our 25 IBU 1.050 OG beer has an apparent attenuation of 80%.  Here is the math on that:

RBR = (25/50) x (1 + (.80-0.7655))

RBR = .5 x (1 + .0345)

RBR = .51725

The idea is that if you have two beers with different attenuations, the consumer will perceive them differently, and this number will reflect that.  This follows the supposition that a higher attenuation would result in a dryer, less malty, beer.  That, in turn, would increase the drinker’s perception of its bitterness.


Overall, there is no single trick to brewing a great session beer, and specific advice is hard to give.  Keep it light in alcohol, high in flavor, and balanced enough to keep out of its own way, and you’ll have something you can drink a lot of without making a fool of yourself or getting bored with it.

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