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My First Decoction Mash Took Forever!

Posted by homebrewdad on 3/18/2014 at 05:23:06 AM


At the beginning of this month, I tackled my first ever decoction mash.  This would be for the traditional bock of my own design (special thanks go out to /r/homebrewing, and especially to Ray Daniels and his superb Designing Great Beers).  I had been reading a bit on decoction mashes, and my friend Rob (author of the superb Munich Dunkel featured in the recipes section of this site) had been raving about how great they were.  I'm a sucker for details and tradition, and so decided that a decoction mash was the way to go for this beer.

For the uninitiated, a decoction mash is the process where, instead of the simple method of mashing (soaking) your grains in water at a certain temperature to hit your desired balance of dryness and body, you instead pull off a portion of your mash, boil it, and add it back to raise the overall temperature of the mash to the desired range.  This boiling creates maillard reactions in the wort, which is supposed to yield a depth of flavor that is impossible to perfectly recreate any other way.

I ended up going with a take on Kai Troester's enhanced double decoction mash schedule.  The original plan was an acid rest @ 97 degrees F, a saccharification rest @ 144 degrees F, a second saccharification rest @ 156 degrees F, and a mash out @ 168 degrees F.  Troester's plan had only a single sacc rest, but also a protein rest @ 133 degrees F.  I'd read about protein rests being blamed for poor head retention and body... so I decided on two sacc rests, instead.  Sure, the decoction was going to make my brewday longer than usual, but it would be well worth it.


This brew would also hold a couple of other firsts for me - I'd get to use my new pH meter (an Omega PHH-7011), as well as my shiny new scale (accurate to .01 gram).  The last time I had brewed, I had made myself aware of my water chemistry, but this time, I would be able to easily measure my mash pH, as well as accurately weigh out my brewing salts.  I set a target water profile based on Munich (albeit with a lower overall alkalinity level) and a target mash pH of 5.5. 

Normally, I am able to warm both my mash and sparge water in my smaller (six gallon) pot; this time, I needed to mash in with about six and a half gallons, so I had to start the water in my main kettle (the eleven gallon pot). 

This small change would be the first in a series of missteps that would lead to the longest brewday (by far!) of my life.

One very nice aspect of the day was my pH meter.  It was easy to calibrate, simple to use, took quick readings, and was a breeze to clean up.  I'm sure that one of the super nice $300 scientific models would be superior, but for brewing, this thing seemed to be fantastic.  I obviously can't speak to how well it will hold up to time, but if it does, it will be a superb value.

I pulled a pH reading ten minutes in to the acid rest, expecting a 5.5 (per Bru'n Water).  Instead, the reading was a whopping 5.94!  I eyeballed a half teaspoon of lactic acid, stirred it into the mash, and pulled a 5.5 on the nose.  Yay me!

A few minutes later, I drew off a large part of my mash for the decoction (in fact, I worried at the time that I pulled too much volume).  Troester recommends that you use 50% - 60% of the total volume for this decoction step.  Looking back, I realize that I should have pulled even more grain than I did, to say nothing of more total volume... cest la vie.  I warmed this part to a middling conversion temp of 152, then started my timer.  Fifteen minutes later, I was at 156, so I cut the heat and added blankets to the pot.  The temp would dip to 148, so I heated it back to 156 and reapplied the blanket, but all in all, this step did okay.  At the end of the forty-five minutes, I boiled the decoction portion for a good half hour, then added it back to the main mash.

Unfortunately, I would discover that I had not, in fact, pulled too much volume to decoct - in fact, the use of every drop of my boiling decoction portion would only raise the main mash temp to 140 degrees F.  I ended up having to add in two gallons of nearly boiling water to hit my rest temp of 144 degrees F.  This bumped my mash pH up to 5.72, so I spitballed another quarter teaspoon of lactic acid, which got me back down to 5.48. 

At this point, I had a decision to make.  I had planned to sparge with two and a half gallons of water, but had just used two gallons to fix my mash temp.  I was afraid that a no sparge method (or near no sparge) would kill my efficiency, so I added two more gallons to my secondary pot and got it warming as I drew off the second decoction for boiling... knowing that this water addition would mean an increased time in my main boil.  

This step did at least work, and I hit 158 degrees pretty easily.  A little stirring, and I was at the target temp of 156 (with my mash pH still at a nice 5.48).  However, I was already a long, long way into my brew day.  At this point, I decided to make an executive decision here, and I deleted the mash out step. 

I began the vorlauf - where you pull the first gallon or so of your runnings, then carefully add it back to the mash tun, which helps to filter out grain fragments, then drained the rest of my wort.  This is usually a quick process, but this time around, it took at least twice as long as normal.  I added my sparge water, stirred like crazy, then repeated the vorlauf/drain process... and hit my first ever honest to goodness stuck sparge. 

I had wort standing in my cooler, but it would barely drain out.  I tipped the cooler up to no avail.  I moved the hose braid around, which helped a slight bit, but far too much wort was still left behind.  I ended up having to dig around with my spoon to get it to all drain.  This digging revealed the issue - at some point, either I or my helpers (my little boys love to stir the mash with my paddle) had managed to crush my hose braid, which was preventing most of my flow.  I'll have to figure out a way to fix this before I brew again!

Finally, the boil began.  Originally, I had planned on a sixty minute boil.  Instead, it took a whopping two hours and fifteen minutes to boil everything off properly!  At least I had plenty of time to make spent grain bread while the boil proceeded.  As always, my little boys really enjoyed throwing the hops into the boil... though they *did* miss the kettle more than usual, resulting in a few more hop pellets being picked up off the ground than is typical.

After the boil, I hooked up my wort chiller to my garden hose, turned it on, and went inside to watch the Walking Dead with my wife and two of my boys.  I disconnected the chiller during a commercial break, then dumped the wort into the fermenter after the show.  I will say that the beer had some gorgeous ruby highlights as I poured it.  Who knows if that means anything, though.

My OG reading was higher than my target, which is very much in line with what I understood might happen with a decoction.  My target gravity was 1.070, but I ended up with a 1.077.  I'll be interested to see exactly where this one finishes!

When all was said and done, this was the longest brewday I've ever had.  I usually brew in five and a half to six hours.  Now understand, I did take some breaks; I went on a walk with my wife and kids, I helped with the baby a time or two, I fixed food for the boys, etc.  Even so, from the moment I started pulling together my gear until the moment I finished cleanup, a full eleven hours had lapsed!

Chilling had gotten the beer to 68 F, so I stuck it in my fermentation chamber overnight.  The next morning, my wort was at 52 degrees F, so I oxygenated with pure O2 and pitched my 3.5 liter starter of WLP920 (Old Bavarian lager yeast).  By the time I got home from work, I already had krausen, as well as some nice airlock bubbles. 

In retrospect, I'm not sure to hope if this beer is absolutely amazing (in order to make the huge time investment worth it), or to hope that it stinks (so as to make sure that I'm not tempted to undertake this process again).  Regardless of how it turns out, I'll be sure to share the results!

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Batch Size (gallons)5.5
Recipe typeAll Grain
Style5B. Traditional Bock
Original Gravity1.070
Final Gravity1.021
ABV6.43% (basic)   /   6.46% (advanced)       [what's this?]
Color23.8 SRM
Boil Time60 min

YeastWhite Labs WLP920 (Old Bavarian Lager)

Munich Malt9 lbs63.2%9
Vienna Malt3 lbs21.1%3.5
Caramel/Crystal Malt -120L 12 oz5.3%120
Caramel/Crystal Malt - 80L 12 oz5.3%80
Wheat Malt, Ger 8 oz3.5%2
Chocolate Malt 4 oz1.8%450

Hallertauer (Boil)2 oz604.8%21.2

for complete recipe (with details like mash and fermentation temps), click here

Tags for this post: decoction, mash, traditional, bock, lager, brew, brewing, double decoction

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Nice post. I was just introduced to decoction mashing through the book Radical Brewing by Mosher and I was really curious to move to all-grain mashing (currently only doing BIAB) just to try it out. It sounds like a lot of work but we didn't start brewing because it was quick and easy! :)

posted by Fsanchez on 3/18/2014 at 03:22:22 PM