The Dunkel Decoction Disaster

A Munich Dunkel is a classic dark German lager. It is tasty, though not quite as malty sweet as its beefed up cousin, the Bock. I’ve never brewed one so I thought it would be a great time to give it a try. This style is very quaffable and I’m thinking that it would be perfect for pulling around the neighborhood on Halloween (going as a Monk this year, been growing the beard since August). So, I did like any brewer would, and I listened to a Jamil show, cruised around thehomebrew talkdark lager pages, and scoured the internet.

I came up with the following recipe:


  • 5.4# Munich Malt (20 EBC; 9SRM) * 4.8# Vienna Malt (3.5 SRM) * 0.6# Caramel/Crystal Malt 80L * 0.15# Carafa III (525 SRM) * 23 IBU Liberty (60 Minutes)

Now as I read about this, the old decoction mash because a common concern. I have never done a decoction mash before, but what the heck. If it is good enough for some of the best German Breweries to still use it, who am I to say no. Besides, what a better way to extend the brew day and try out a new technique. I settled on a single decoction, Mash in for a protein rest with 6.74gal of water to hold at 122. Decoct 2.8gal of the thick mash and boil. I boiled and stirred and boiled and stirred for what seemed an eternity. In the fall, when the humidity is up already in Virginia, there is nothing quite as enjoyable as standing over a propane burner, stirring mash. Lost a few # water weight during that mash. Now what was supposed to happen is that I was supposed to return it to the mash tun and it would bring the temperature up to 154 for the Saccharification rest. However, it didn’t do it. I don’t know if I messed up on the measuring or something else went wrong, but when I stirred it back into the main mash, it raised to 138. Crap.

So, I quickly reconfigured the mash tun and boil kettle, remembering to rinse out the husks from the decoction, it will cause problems later if you do not, into a 2 vessel recirculating mash system and raised the wort temperature via direct fire of the boil kettle. I suppose this is what I should have been doing all along. Perhaps a step mash would be better than a decoction for me at this time. Who knows. I got it up to 154 and rested until conversion. I ran it off and batch sparged then boiled a 120 minute boil (I was afraid I was undershooting the SG so I wanted a little concentration. Hit gravity perfect at 1.051. Chilled via recirculating through a plate chiller and then threw it into a keg in the fermentation chamber set to 52.

During the process, there was quite a mess made in the old brewing corner of the garage. It was messy, I did some stupid things with the hoses, and stickiness ensued. There will probably not be any way to replicate this particular batch (at least I hope not). I’ll pitch in the morning the 2L 2 vials of WLP833 I’ve built up and let it run. I’ll try to fully implement the spunding valve on this one. We shall see what happens.

Father, Husband, Brewer, Professor

Middle aged guy trying to keep it all together and figure out how to best navigate the world as it is. Technology geek, practitioner of fermentation sciences, researcher, biologist.