Most of the all-grain brewing systems you hear about have three barrels: a mash tun, a hot liquor tun and a kettle. See What I learned about brew systems a “Big Brew” for more details on how these systems are usually configured.
A little while ago I heard about a two-barrel system, and I wondered how something like that could work. The only thing that made sense to me was that you’d have a kettle and a mash tun. You’d heat up your strike water in your kettle, then add it to the mash tun. Then you’d add all your sparge water to the kettle, and you’d recirculate water between the kettle and the mash tun until you reached the gravity you wanted.
There’s one clear disadvantage to this method. You end up washing your grains with wort that already has dissolved sugars in it, and there’s no way that would be as efficient at extracting sugars from the grains with clear water.
But I decided to give it a try. Since this was just a test, I didn’t go whole hog on the equipment. I set up a very simple, low-tech method for trying out a two-barrel solution.
Since the wort was going to be recirculating through the grains, I figured this was a job for fly sparging, so I pulled out my (very simple) fly sparging setup. The fly sparging arm sits inside the top of my picnic-cooler mash tun, and I pour the sparge water into the funnel on the top.
I’ve used this before, and it works like a charm. You pour the sparge water into the funnel, the fly sparging arm dribbles the water onto the grains, and the wort is slowly extracted from the mash tun.
That brings up one of the problems my two-barrel experiment. When you’re sparging with clear water, the system works great. When you’re recirculating wort, little bits of gunk clog up the the fly sparging arm. I should have filtered the wort before I poured it back through the sparging apparatus.
This happened several times. I had to stop, disassemble the fly sparging arm, clean it out, then put it all back together.
The recirculating process sorta resembles a decoction mash, because you need to keep heat on the brew pot to keep your wort / sparge water at the right temperature.
My goal was to recirculate the same volume I would typically use in a batch sparge, but when I got to that point the gravity wasn’t where I expected it to be, so I kept recirculating / sparging.
I never got close to my target gravity, so this system — at least this time around — was very inefficient. About 80% as efficient as my normal batch-sparging method.
However … the beer turned out great. I was aiming for the higher end of an alt, and I ended up with a pretty mid-range alt. It’s very malty and very good.
I’m going to try this method again sometime and I’ll report on the results.