by Mike Retzlaff
The concept of brewing subdued gravity beers isn’t particularly exciting but I hope I’ve generated some interest in doing just that. Which type of brewing procedure is the most suitable for you depends on your skill set and the equipment available for your use. Let’s go through the several methods available and look at some of the positive and negative aspects.
By far, the easiest way to brew Small & Session beers is through the parti-gyle or 2nd runnings process. In parti-gyle, you collect the initial wort for your main batch. Then you can run more water through the mashed grist (usually batch sparge) to collect a 2nd run of wort. Commercially, the 1st and 2nd runnings are often combined to produce the initial batch while the 3rd and 4th runnings are made into progressively smaller beers. If you ponder the wasted sugary grist normally discarded after the lauter and sparge, you should be able to see the value of the parti-gyle method. Besides, most of the hard work is already done and it’s almost like getting a free batch of wort!
Session beers require a larger concentration of sugars than Small beers so it would be desirable to start with a mash from a heavy duty beer or from a Brew Off mash. Because of the massive quantity of grist, this would work with almost any style of Brew Off beer and you could get multiple remnant 5 gal. batches. Brew Offs have garnered 60% to 75% brewhouse efficiency over the last several years with only a few exceptions so there’s lots of sugars left for someone to retrieve. Talk with the Brewmaster before making any plans.
A brewer might offer assistance to a fellow brewer in exchange for the 2nd runnings from their next batch. Various brewing sugars can be used to adjust the pre-boil gravity for a Small or Session beer if needed.
When utilizing parti-gyle procedures, it is important to acidify the sparge water to pH 5.8 or less as most of the buffers have left the mash during the first lauter. This will help negate the extraction of polyphenols (tannins) and keep the beer from becoming astringent. I acidify my sparge water anyway to assist the finished beer in getting down into the pH 4.6 neighborhood after fermentation which makes for a better balance of flavor and a better drinking beer.
An example of the parti-gyle style of brewing is Anchor Brewing’s Old Foghorn Barleywine. Once the wort is run off, the second runnings are collected for a small beer. If you are collecting from your own heavy duty mash, that’s one thing. If it is someone else’s mash, that other person is the one with control over mash temps and through that, the ability to adjust wort content such as dextrins. This is certainly a trade off and especially problematic for use in a Small beer. A calculated amount of malto-dextrin powder or even lactose can be added to the kettle to compensate.
Brew In A Bag
When a “spent” mash isn’t available, we can utilize the BIAB method. This can easily be tailored in brewing to a particular OG. BIAB is well suited to 2½ or 3 gallon batches. It’s possible to use this method for 5 gallon batches but it may not be practical. If you overload your strainer bag, bad things can happen. When brewing Small beers, the grist bill is very light so the concern would shift to the volume of the kettle. Of course, the great thing about BIAB is your batches of beer can be held to just several gallons. It promotes a quick turnaround which allows you to tweak recipes to fit your taste and style requirements a little faster.
Unless your normal brews are rather big beers, Session beers should not be much different than a regular batch. Whether you use brewing software to calculate your own recipes, or simply follow something out of a book or magazine, Session beers shouldn’t be much of a change to your normal brew day procedures. Small beers, on the other hand, seem quite different, as it’s a little scary to see just how little goes into the mash tun when brewing these beers.
Water evaporates and sugars concentrate as wort boils. I know with my set-up that I’ll pick up 2 gravity points with every 15 minutes of boil. With a 60 minute boil I get 8 points, 10 points with a 75 minute boil, and 12 points with a 90 minute boil. That, added to the pre-boil gravity, will invariably indicate my post-boil OG. Kettle geometry changes everything so you really need to understand your own equipment and figure such things into the recipe.
Small beers have little ability to hide flaws and require due diligence on the part of the brewer to make sure everything is done properly. Session beers are closer to our normal brewing but can still present a challenge.
One of the things required for Small beers (and low end Session beers for that matter) is to manage the mash temps to produce dextrins. You’ll want to be creative in your hopping methods to add depth and a variety of hops to add distinctive flavors to the beer. Small beers require a thoughtful choice of yeast to keep ferment attenuation in due bounds. That also leads us to keep an eye on ferment temperatures. You can brew a normal beer with a friend and split the final beer between two ferment buckets and top up each before adding the yeast. There are all sorts of ways to get where you want to go.
I offer both Small and Session beer recipes in other articles. Take a look and give them a try.