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Old 11-10-2012, 08:58 PM   #1
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Default BIAB and decoction mashing

I'm looking to brew a Czech Pilsner based on the "Polka Dot Pilsner" recipe in 'Radical Brewing'. I usually do BIAB full volume mashes. This recipe calls for a decoction mash using 1/3 of the of mash volume. My question centers on the volumes. Since I will be mashing with around 8.5 gallons, should I try to pull about 3 gallons of mash off and do the decoction steps or is there a better way? Is the decoction really necessary? I've never tried it before and in the book, Mosher gives an alternative to the decoction using Munich and/or Vienna malts, does that give similar results or would I be missing something? Just not sure how to approach this one. TIA!

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Old 12-03-2012, 09:15 PM   #2
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I do decoctions when the style calls for them. I have done the full triple decoction, but these days, I am more apt to do a step infusion (adding boiling water to my M/LT) and then a single decoction for mash out (boiling about a third of the mash for 15-30 minutes, then adding it back in before sparging). That way, I don't have to worry so much about hitting my temperature exactly at the end--and it's a bit simpler.

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Old 12-14-2013, 04:03 AM   #3
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I hate bringing back old threads, but has anyone been doing this for certain styles?
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Old 12-14-2013, 12:40 PM   #4
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I've done it once. Actually, doing BIAB makes it easier to remove just the grains to boil. I lift up the bag just enough to bring some of the grains out of the water then scoop out what I want. I found it a little more difficult to control temperature (mostly because of my small volume brewing), but it was my first time doing a decoction mash and I was working my way through learning a new process...
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Old 12-15-2013, 02:30 AM   #5
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I've done decoction mash BIAB several times. Instead of the general rule of pulling 1/3 of the mash, I've used the estimates from the BrewPal app to figure out how much volume to boil and have come pretty close (within a degree or 2) each time. And I generally do it for my Belgian styles.
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Old 02-20-2015, 06:55 PM   #6
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I've been having a go at single decoctions w a bag, but can't figure out how decocting for the mash out should work with the sparge/teabag process. Since the mash out is taking care of the temp change, do i just heat the sparge water less and do the drain/teabag process as before? Would it make more sense to do the decoction at an earlier step if the style/malt calls for a rest (bock/Weyerman's Munich)?
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Old 02-20-2015, 07:10 PM   #7
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Up to you. A number of blind trials have shown that Decoction mashing provides no noticable difference.

I do it occasionally when it is to style, but I personally do a "full volume" decoction, IE all of the grains at once.

Mash for the length of time that you want, then drain off most of the wort volume and bring the resultant grains and a bit of water (that is a couple of fingers below the top of the grains) to a boil for 15 minutes and done.

Its rather easy for me with my BiaB method as I normally do a 60% volume mash in my main 6 gallon pot and a 40% volume soak in my 5 gallon pot after 60 minutes, for 10-15 minutes.

So when I do a decoction, I do the regular mash in the main pot, I then dump the grains from the grain bag in to the 5 gallon pot with only 20% volume in that pot (and 80% in the main pot instead of my usual 60/40). That is generally enough to keep the water below the level of the grains enough that I should be getting good malliard reactions going on.

In theory. I certainly get some nice sludgy goodness at the bottom of the pot that I have to scrape off even with vigorous stiring.

I frankly don't trust doing this with the grains still in the bag. Once I am done I just dump it all back in to the main pot and strain with the bag still in the main pot.
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Old 02-20-2015, 07:41 PM   #8
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My wife and I (she did the decoction, I watched... ) did one triple decoction for a historic gruit that we brewed. Gruit turned out great, decoction... I might never do a triple again.

We used my RIMS to manage the step temperatures post adding the decoction so it was more about getting the flavors by removing a thick part of the mash and boiling it then temp raises.

I think there is a value in a single decoction for flavor, but after that... if you can just step mash with re circulation or something.

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