thoughts/observations/questions on my first Decoction Mash...

So I'm brewing up a Weizen and figured this would be a good time to bite the bullet and try a decoction mash for the first time. Here's the grain bill:

4.75 lbs Pilsener (~47%)
4.50 lbs Wheat (~45%)
0.50 lbs Munich (~5%)
0.31 lbs Acidulated (~3%)

So I created a mash schedule using ProMash, and here's what the numbers came up to:

Glucan Rest 97*F Infusion, Temp 99*F, 18.00 quarts, 1.79 qt/lb ratio
Protein Rest 122*F Decoction, Temp 212*F, 4.81 quarts, "decoction thickness" 1.0
Amylase Rest 154*F Decoction, Temp 212*F, 7.86 quarts, "decoction thickness" 1.0

Everything starts of pretty well; I mash in for the protein rest just fine, hit numbers for temp dead on. After the rest, I pull off the (approx.) 4.81 quarts, boil it and dump it back in to the mash tun. BUT, I only hit 118*F instead of the expected/desired 122*F. No biggie, I RDWHAHB on that one, but decide that I'll just pull a little more for the 2nd decoction.

So I pull a full 8 quarts after the protein rest, boil it, dump it into the mash tun. This time, after a good stirring, I'm only hitting 150*F (at best...). I figure I'll pull another quart...I quickly boiled it in the microwave, then add back to the mash...still barely at 151*F. Pull another TWO quarts, quick boil in the microwave, and I finally settled to ~152-153*F. At this point I call well enough alone, and that's where I stand now...I'm about a half hour from sparging.

To recap, I ended up adding a total of 11 quarts of boiling wort to the mash to hit my amylase rest temp, and the calculations said I needed only 7.8 quarts...

So here's the question(s):
- Why did I not hit temps with the calculated numbers?
- Is this just a quirk of my own setup that I need to learn to deal with?
- Is there some faulty assumption or input in the software that gave me wrong numbers?
- Are my temp measurements off? (I don't think they are, I used both a digital thermometer and a glass/alcohol thermometer, and they are correlating pretty well...)
- What exactly is the "decoction thickness," and how does it affect things if it is altered (I used the default, which was "medium," and was noted as "1.0")

Sorry for the long post, and thanks in advance for any advice from those more experienced with decoction!

For hefeweizens a more common approach now (with well modified grains) is dough in at 97F (if you need the acid rest) then 113F, 148F, 158F. If you can't go from 113 to 148 you might want to stop off around 130F for a brief rest. An unnecessary protein rest will start breaking down proteins you need for mouthfeel and head retention. However, lots of people do different rests and produce delicious beers so don't feel like you have to do something different.

When you pull decoctions you should pull from the thickest part of the mash so you're getting a lot of grain. The denser decoction will hold more heat and give you more accurate increases in temperature. It also allows you to boil the grain and break them open so more starches are available for conversion. If you only pull liquid it's hard to get the temperature to come up correctly. The other thing that is really important is to stir your mash for a few minutes to thoroughly and evenly raise the temperature before you even check the temperature. If you just dump the decoction in without thorough stirring you aren't going to get an accurate read and you're probably going to end up adding too much heat.

I don't think you're getting the full benefit of the decoction mash by boiling in the microwave.

I don't have my spreadsheet in front of me, but those decoction volumes seem low. Did you validate the Promash decoction volumes with other calculation methods (i.e. John Palmer's calculations)?

Kaiser has some good videos on decoction mashing that are very helpful. I think they are in the sticky at the top of this section.

One thing I notice is that Kaiser (and others I've read) recommend pulling 10 to 20% extra for the decoction. This allows you to add back gradually until you hit the desired temp. If you have any left, let it cool to the rest temp and then add back.

Also, when you hit 118 instead of 122, your next calculations are affected. The software told you to pull 4.81 qts and it assumed you would add that back to the main mash at 122. If the main mash only got to 118, (and may have dropped further during the rest), those differences from the software assumptions need to be accounted for.

Thanks for the quick reply! (I'm just finishing the boil now...)

ReverseApacheMaster said:

For hefeweizens a more common approach now (with well modified grains) is dough in at 97F (if you need the acid rest) then 113F, 148F, 158F. If you can't go from 113 to 148 you might want to stop off around 130F for a brief rest. An unnecessary protein rest will start breaking down proteins you need for mouthfeel and head retention. However, lots of people do different rests and produce delicious beers so don't feel like you have to do something different.

Click to expand...

I did read about considering a rest in the one 'teens...supposed to increase precursors for the clove-y phenols... This is partly the reason why I didn't stress too much about not hitting temp on my first decoction. I'll have to read up a lot more on the various rests and what they can contribute...

ReverseApacheMaster said:

When you pull decoctions you should pull from the thickest part of the mash so you're getting a lot of grain. The denser decoction will hold more heat and give you more accurate increases in temperature. It also allows you to boil the grain and break them open so more starches are available for conversion. If you only pull liquid it's hard to get the temperature to come up correctly. The other thing that is really important is to stir your mash for a few minutes to thoroughly and evenly raise the temperature before you even check the temperature. If you just dump the decoction in without thorough stirring you aren't going to get an accurate read and you're probably going to end up adding too much heat.

Click to expand...

So I'm already seeing one thing I did wrong! I did only pull liquid, as if I was starting to sparge. I had no idea (guess I have yet more homework to do!) that you were supposed to pull actual mash contents, but in that respect the concept of Decoction Thickness makes much more sense!

It's funny, b/c I kind of thought boiling grains was a "no-no" in general -- releasing excessive tannins, and all that.

I did, indeed, give good periods of thorough mixing before recording temps (with two different types of thermometers, as noted).

ReverseApacheMaster said:

I don't think you're getting the full benefit of the decoction mash by boiling in the microwave.

Click to expand...

Yep, I did actually do a regular boil for the main decoctions...I only used the micro for the 2 aliquots I pulled to get my mash temp up to where it needed to be....

Tun thermal mass. You have to heat the vessel as well as the mash.

The decoctions returning to the main mash are never truly at boiling temp.

Decoction mashing really pays off on a Hefeweizen IMO. Continue using whatever calculations you had been, but pull an extra 20% and let it cool to the next rest temp if you don't need it.

texasbrewer73 said:

I don't have my spreadsheet in front of me, but those decoction volumes seem low. Did you validate the Promash decoction volumes with other calculation methods (i.e. John Palmer's calculations)?

Click to expand...

No, I didn't validate with any other source, but used a pretty well known software (ProMash)...I will say though that your guestimation matches my experience today, although as I've already realized, some of the issue may be that I only pulled wort, rather than complete mash contents. As someone else also observed, I also really didn't correct for the lower temp of my first decoction when I did the second.

Overall, I was pretty much winging things as a first attempt.

This brew was as much as anything just a big starter...I plan on doing a pretty big wheatwine (sort of a Terrapin Gamma Ray clone) and will use the same WLP300 strain. I had thought I should do a decoction with such a big wheat load, and wanted to hammer out some procedures on a smaller beer...so far, I've definitely learned a lot, and feel like I'm getting the gist of what I should be doing/thinking about when I do the big wheatwine...

I actually wanted to give a big fat plug to Terrapin...I e-mailed them about Gamma Ray, and actually got an e-mail back directly from Spike (owner/head brewer) with recipe tips/hints! The proportions on the grain bill and yeast recommendation are from him...

JakeFegely said:

Kaiser has some good videos on decoction mashing that are very helpful. I think they are in the sticky at the top of this section.

One thing I notice is that Kaiser (and others I've read) recommend pulling 10 to 20% extra for the decoction. This allows you to add back gradually until you hit the desired temp. If you have any left, let it cool to the rest temp and then add back.

Click to expand...

You know, that sticky caught my eye earlier today...the reticular activator having decoction on the brain...I just never noticed it before!

944play said:

Tun thermal mass. You have to heat the vessel as well as the mash.

The decoctions returning to the main mash are never truly at boiling temp.

Decoction mashing really pays off on a Hefeweizen IMO. Continue using whatever calculations you had been, but pull an extra 20% and let it cool to the next rest temp if you don't need it.

Click to expand...

Great points...I really don't know exactly how to account for the mash tun itself in the software, but I've learned to work around it with simple infusions.

I do like the adding 20% idea (and double corroboration on that point, excellent!)...I'll probably do something like this on my next attempt...