[gcupples]

I've been having some really highly attenuated beers (85% and up regularly). I got into the habit of 90 minute mashes with a really fine crush while I was on a saison kick a year ago. I always attributed the high attenuation to the low mash temps I was using, the yeast (French Saison typically), and the (sometimes warm) ambient temps I was fermenting at.

Anyways, the short of it is I never stopped with the really fine crush and the 90 minute mash. I had them firmly in the category of "can't hurt, might help" as far as conversion went.

But now that I've acquired the coveted chest freezer to ferment in, I'm getting back into making stouts the right way (it's about the only beer the gf will drink)

Recently, I made an Oatmeal Stout. I mashed at 158* for 90 minutes, had an OG of 1.056, and fermented at 64* for 7 days. SG was at 1.010 before I let it free-rise to 72*. Two days later, SG is at 1.008 (Final Gravity is TBD). The result is a beer that's simply out of balance: too bitter/harsh/thin because of the lack of residual sweetness. The batch before this was a Belgian Dubbel that had the same end result.

I feel confident that it's not a sanitation or a thermo/hydrometer calibration issue.

I'm going to probably revert back to a coarser crush and a shorter mash. Any thoughts on which is likely to contribute more to the issue?

The TL;DR summary is: are extended mash times and my fine crush giving me a wort that's too fermentable? Even when mashing on the hot side and fermenting on the very cool side? Or is it something else that maybe I haven't considered?

[reverseapachemaster]

You're probably right that your mash is the source of your problems although it might be a few other issues than the length of the mash. The mash duration certainly will give you a highly fermentable wort but as mash temperatures go up the benefit of the longer mash goes down because conversion happens at faster temperatures the higher the temperature. However, if the temperature is dropping by more than a few degrees during the mash then you might be heading into beta territory and you are getting conversion for a much longer period of time and those longer chain sugars are getting broken down into more easily fermented sugars. That could certainly explain your attenuation but I'd want to know what kind of efficiency you are getting from the mash (along with the brewhouse as a whole).

It's also possible your thermometer is incorrect and you are mashing lower than you think and getting significantly more beta conversion than you want.

I'd also take a look at your water profile and mash ph to see if you are getting more acrid character out of the darker grains due to a low mash ph. If you experience good conversion than the water profile might be fine for the mechanics of the mash but not necessarily for the flavor of the beer. A water profile that produces a good mash ph for saison isn't necessarily the same for darker beers.

The attenuation could also be caused by infection somewhere in the process, yeast selection, fermentation temperature (i.e. your thermometer might be reading much lower than what it really is), etc. but I think the mash is at least partially responsible here.

[dmtaylor]

90 minutes is hurting you.  It is best to take your mash time down to 40 minutes.  I have been doing short mashes of 40 minutes for many years and love the results.  30 minutes will get your attenuation down even lower but probably a little too low for premium enjoyment in my experience.  Try 40.

[toby]

The TL;DR summary is: are extended mash times and my fine crush giving me a wort that's too fermentable? Even when mashing on the hot side and fermenting on the very cool side? Or is it something else that maybe I haven't considered?

Few possibilities would be:

1) You're mashing too long for your temp.  90 minutes is typically what I do for a lower temp, highly fermentable mash since beta amylase works more slowly than alpha amylase.  You can cut your mash time in half for most modern malts in the high 150s.
2) Your crush and the type of malt may be causing additional problems for you.  Pulverizing the husks will lead to extra tannin extraction.  With Pils malt, that may only contribute some graininess, but with dark malts, you'll get extra bitterness and astringency.
3) You also didn't mention water chemistry.  Water with a high pH (sparge pH above 6.0) can lead to even higher tannin extraction.  Are you doing anything to treat your water?

[gcupples]

You're probably right that your mash is the source of your problems although it might be a few other issues than the length of the mash. The mash duration certainly will give you a highly fermentable wort but as mash temperatures go up the benefit of the longer mash goes down because conversion happens at faster temperatures the higher the temperature. However, if the temperature is dropping by more than a few degrees during the mash then you might be heading into beta territory and you are getting conversion for a much longer period of time and those longer chain sugars are getting broken down into more easily fermented sugars. That could certainly explain your attenuation but I'd want to know what kind of efficiency you are getting from the mash (along with the brewhouse as a whole).

The mash temperature only drops about 3 degrees over the course of the mash. Brewhouse efficiency is consistently 70%

I'd also take a look at your water profile and mash ph to see if you are getting more acrid character out of the darker grains due to a low mash ph. If you experience good conversion than the water profile might be fine for the mechanics of the mash but not necessarily for the flavor of the beer. A water profile that produces a good mash ph for saison isn't necessarily the same for darker beers.

2) Your crush and the type of malt may be causing additional problems for you.  Pulverizing the husks will lead to extra tannin extraction.  With Pils malt, that may only contribute some graininess, but with dark malts, you'll get extra bitterness and astringency.
3) You also didn't mention water chemistry.  Water with a high pH (sparge pH above 6.0) can lead to even higher tannin extraction.  Are you doing anything to treat your water?

I've used dark grain in the past with this water and haven't had any issue with an acrid or tannic character. I think it's mostly the lack of sweetness that's highlighting the out-of-balance-ness.
I assume my water is pretty middle of the road. I don't mess with it beyond running it through a charcoal filter, mostly out of laziness. I live in NYC and the water is generally considered good for brewing. If anything, my mash pH is on the lower side (based on readings from those cheap pH strips).
 

90 minutes is hurting you.  It is best to take your mash time down to 40 minutes.  I have been doing short mashes of 40 minutes for many years and love the results.  30 minutes will get your attenuation down even lower but probably a little too low for premium enjoyment in my experience.  Try 40.

I dig your style. I think this is going to be my first adjustment and I'll see where I stand after that.

[bboy9000]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

[HoosierBrew]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

FWIW I fixed my harsh stout problem by raising pH. Kept crush the same - made a huge difference.

[bboy9000]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

FWIW I fixed my harsh stout problem by raising pH. Kept crush the same - made a huge difference.

Yes, I raised my mash pH with mineral additions.  In my case the the low pH may have been caused by the powder-like crush Jamil recommends for the roasted grains in his dry stout recipe.  I won't do that again.

[toby]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

FWIW I fixed my harsh stout problem by raising pH. Kept crush the same - made a huge difference.

Yes, too low a pH (higher acidity) will lead to a different harshness.  That's why water chemisty is your friend.  There is no water that's universally good for brewing.  Certain waters will brew certain styles better, so you have to work around it brewing a different style.

[bboy9000]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

FWIW I fixed my harsh stout problem by raising pH. Kept crush the same - made a huge difference.

Yes, too low a pH (higher acidity) will lead to a different harshness.  That's why water chemisty is your friend.  There is no water that's universally good for brewing.  Certain waters will brew certain styles better, so you have to work around it brewing a different style.

Yes, I learned my water is pretty good for   APA.  For everything  else I use Bru'n Water.

[HoosierBrew]

In my experience I've had harsh stouts probably due to too fine a crush and too low mash pH.  I changed both at the same time so I'm not sure which variable made the difference.

FWIW I fixed my harsh stout problem by raising pH. Kept crush the same - made a huge difference.

Yes, I raised my mash pH with mineral additions.  In my case the the low pH may have been caused by the powder-like crush Jamil recommends for the roasted grains in his dry stout recipe.  I won't do that again.

Ok, gotcha. Didn't see the reference to JZs stout.

[gcupples]

Yes, too low a pH (higher acidity) will lead to a different harshness.  That's why water chemisty is your friend.  There is no water that's universally good for brewing.  Certain waters will brew certain styles better, so you have to work around it brewing a different style.

Yeah, I might have been painting in broad strokes in my first reply. I understand that water chemistry ideally should cater to the style. But I also think for my purposes (I'm not trying to brew a flawless, award-winning beer), so long as nothing is egregiously wrong with the water, I should be able to brew a decent beer. And I have brewed balanced stouts with this water. What I'm really after here is fixing the over-attenuation problem.

[toby]

Yes, I learned my water is pretty good for   APA.  For everything  else I use Bru'n Water.

Local water here is really good for dark beers, although the sodium level is on the high side for lighter beers.  It's workable, though.  Overcoming the carbonate levels and pH are a challenge for really light, delicate styles.  I've managed to make a pretty decent kolsch with it in the past, despite my hop snafu on the last batch.

[HoosierBrew]

Most of the water in Central Indiana is just plain crap, so I made RO, TDS meter and Bru'nwater my friends. Loving the difference they make.

[bboy9000]

What I'm really after here is fixing the over-attenuation problem.

I understand that but with descriptions such  as bitter/harsh we immediately thought of mash pH due to roasted grains.  Water chemistry can change seasonally as well.  If you believe over-attenuation is a problem have you tried using different yeasts?