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Dark beers and under attenuation - pH issue?

Mashing
#1

I’ve been having this issue for several batches. Any darker beer that I brew is under attenuating, usually finishing around 1.020. I’m wondering if this is a pH issue. Usually I mash without the dark malts and add them at the end of the mash before sparging. I usually adjust my water with calcium chloride, but I haven’t been very strict about it. I used to use Bru’n water a lot more, thinking maybe I should start paying a little more attention to that again.

Anyone know if that may be the issue? I can’t really think of much else…

For instance, the last batch I brewed was 3 gallon batch, brew in a bag method, oatmeal stout with 5 or 6 lbs of pale malt, 6oz of caramunich III, and about 6oz of blackprinz malt 500L (put in at the end of the mash). Mashed at 153-154F. OG was 1.060 which was about 78% efficiency.
It never formed a krausen, which I thought was very odd. Pitched US-05, shook the carboy, and it took off the next morning. Fermented fairly vigorously, but with no krausen, never seen that before. Right now the OG is at 1.020 after a week and it seems to me that fermentation has slowed nearly to a stop. I don’t see it coming down 5 or 6 points…
All of my lighter beers are attenuating just fine…so that’s why I think it may be a pH issue.

Any insights?

#2

Oatmeal does have soluble fiber that is probably affecting your FG. I’d guess if you didn’t have it in there you might be closer to 1.015. Otherwise your recipe and method seems reasonable, not too much crystal, a good mash temp, adding dark malts late in mash to prevent extreme mash pH adjustments.

You could try mashing at a lower temp, maybe your thermo is reading a little low. If its a bimetal they do have a tendency to wear out and start reading low.

#3

I find that a lower mash pH tends to create a more fermentable wort that ends with a lower FG and the body is also reduced. I agree that the other grains are probably reducing wort fermentability.

#4

[quote=“tom sawyer”]Oatmeal does have soluble fiber that is probably affecting your FG. I’d guess if you didn’t have it in there you might be closer to 1.015. Otherwise your recipe and method seems reasonable, not too much crystal, a good mash temp, adding dark malts late in mash to prevent extreme mash pH adjustments.

You could try mashing at a lower temp, maybe your thermo is reading a little low. If its a bimetal they do have a tendency to wear out and start reading low.[/quote]

If the thermometer is reading low he should be getting a more fermentable wort.

#5

Well, a lot of the time, I was using my Thermopen for mash temp and adjusting it. This seems to be an issue for many dark beers I’m brewing, even with high pitch rates, and not necessarily with oats in the mash. Perhaps I am mashing too high. I’ll have to do some experimenting to see what the issue is. I’ve been using tap water and treating it with camden and such. Before I had this issue, I was using RO and adjusting with Bru’n water. I may start doing that again as my first trial and error. I think that brewed better beer anyway, it’s easier to work with a blank slate.

Thanks, guys. So this may not be a pH issue after all…

#6

If you’re adding your dark malts late in the mash then you’re not getting the acidic benefit from them in your mash, and your ph may be high because of that. Going back to RO water & adjusting the ph based on the grain bill (less the dark malts if you add them late) should lower your ph. Mashing lower (~150) should help as well. Cheers!!!

#7

When making a dark beer, I adjust the pH with whatever portion of the roasted malts brings it in line, then add the rest at the end of the mash prior to boosting the temp (I no-sparge) - no issues with fermentability using this method. But if you’re adding all the dark malt at the end without giving them enough time to convert, I wonder if you’re adding unfermentables.

#8

[quote=“Nighthawk”][quote=“tom sawyer”]Oatmeal does have soluble fiber that is probably affecting your FG. I’d guess if you didn’t have it in there you might be closer to 1.015. Otherwise your recipe and method seems reasonable, not too much crystal, a good mash temp, adding dark malts late in mash to prevent extreme mash pH adjustments.

You could try mashing at a lower temp, maybe your thermo is reading a little low. If its a bimetal they do have a tendency to wear out and start reading low.[/quote]

If the thermometer is reading low he should be getting a more fermentable wort.[/quote]

If the temp is actually 160F and the thermo is reading 154, he’d get lower fermentables/higher body. Thats what I mean by reading low, actual > observed.

#9

I thought about that explanation but unfermentables in crystal shouldn’t really be affected by mashing, and a 500L malt shouldn’t have much in the way of fermentables either.

#10

That seems likely…it’s only 25 cents a gallon for RO, which is nice. So I’m going to give that a try again anyhow. What I used to do was build my water for an amber colored wort, then add the dark malts at the end. It seemed to work well. But I may do was Shade said and add some of the dark malt at the beginning, and the rest at the end. That could be something to try before switching back to RO, as the pH may be too high to begin with.

Thanks for the input guys, if y’all have any more ideas, post 'em!

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