All Grain Brewing: Boil Trub and Boil Volume

Recipe size used to be simple. If I wanted to make 2.5 gallons of beer, I designed a recipe for that amount, boiled however much water I wanted, and topped off to 10 quarts with distilled water. I hit my OG every time and ended up with exactly 10 quarts in the keg. I'm learning more and more that it isn't so simple.

First off, when doing a full boil, there is no top-off. Sure, if you end up with less than intended you can top off a little, but you can't go the other way - if you have too much water, you can't just make it disappear. You'll end up with beer of a lower gravity.

Which brings me to number two, evaporation rate. This is tough. Evaporation rate differs based on how long you boil, the temperature, humidity and pressure of the room you're in, the pot you're using and what you're boiling. I suggested in an earlier post that you test the evaporation rate of your pot with water, but that is only an approximation. Beer wort will evaporate at a lower rate in practice than what you measured from your water test.

Let's say you have your evaporation rate down. After your boil, you have exactly 10 quarts of wort. Are you really going to dump all of that in? Hell no. You've got hops in there, absorbing up all your water. That isn't coming out. If you're doing all grain, you have *tons* of break material (reminder: cold break is the gray-ish material that separates from your wort when it cools). That break material should mostly stay in the pot if you can help it.

All in all, you'll be lucky to get 8.5-9 quarts of your boil. Sure, you could dump in all 10 quarts, but then you'll end up with more fermenter trub, which brings me to number four...

Fermenter trub. Stuff is going to fall out of your beer and settle during fermentation. When you rack to secondary or a bottling bucket, that material won't come with it, and your total volume of usable beer will be less. At this point, if you're doing a 10 quart all grain batch, you will probably have about 8 quarts, or 2 gallons.

The solution is usually to just make more beer. Design your recipe for 12 quarts (3 gallons). After your wort has cooled, remove as much boil trub as you can. You can either strain it out somehow or let it settle and only rack the clear wort into your fermenter. This means leaving 1-1.5 quarts in the kettle, and 10.5 quarts in the fermenter.

The method I use is to first create a whirlpool in the kettle while it is still hot by stirring the wort immediately after the boil and adding the aroma hops. Once the wort cools, break material and hops will tend to settle in the center in a cone. Then I transfer from the edge of the kettle, since most of the trub is in the center. I siphon from the kettle into a sanitized bucket. Then I allow the trub to settle out for an hour or two, or until I have at least 10-11 quarts of clear wort. With most beers, the difference between the trub and the clear beer will be very obvious. Tilt the bucket back to get the trub away from the spigot (make sure the spigot is sanitized!) and rack from the bucket to the fermenter with some tubing. Make sure, using the markings on your bucket, that you get at least 10 - 10.5 quarts in the fermenter. I generally end up with 2.5 gallons during bottling when I use this method.