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Home Brew Forums > Home Brewing Beer > All Grain & Partial Mash Brewing > Attenuating too low
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Old 10-31-2009, 08:10 PM   #1
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Default Attenuating too low

Hey all,

I've recently started brewing all-grain and have about 4-5 batches under my belt. Everything has been working out well with my system with the exception of some of my brews seeing over 80% attenuation when I'm expecting 70-75%. I'm wondering if it is just the way my system is working and I might need to just mash a few degrees higher. Here are some details of recipes that went way lower than planned however they taste good just a little less body than I'm shooting for. I've been mashing for 60 minutes and stirring very well at dough in and another 3-4 times during the full 60 min mash. I'm doing a single infusion batch sparge at an initial ratio of 1.33 qt/lb. Lastly, I've calibrated my thermometers and they're giving true mash temp readings so I know I'm hitting the temps that I've recorded.

Magic Hat #9 clone:
- Mash settled at 154 after dough in and ended at 151 after 60 min.
- Used wyeast 1968 London ESB which is supposed to have ~69% attenuation... I pitched a 1L starter
- Fermented right at 68 degrees for two weeks
- OG 1.052
- FG 1.009 (I was expecting mid-teens but I got over 80% attentuation!)

My 60 minute clone:
- Same exact deal as above... mash settled at 154 after dough in and ended at 151 after 60 min
- Used wyeast 1187 Ringwood ale which is supposed to have ~70% attenuation - I pitched a 2L starter
-Fermented right at 68 degrees for two weeks then dry hopped for a week in secondary
- OG 1.061 (a little low due to low efficiency from bad crush)
- FG 1.011 (I was expecting mid/high-teens but got 81% attenuation again!)

Should I just try mashing higher on my next go-arounds?

Any advice would be appreciated... not sure if anyone has had similar experiences. Oh, I do want to note that my extract brews do seem to attenuate by the expected amount. This really leads me to believe my issue is somewhere in the mash.

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Old 10-31-2009, 08:16 PM   #2
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At 151, you're mashing for very fermentable wort. If you mash at 154, you'll notice a bit less attenuation. Also, double check your thermometer- if it's off even 2 degrees, you could be mashing at 149!

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Old 10-31-2009, 08:51 PM   #3
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Thx for the reply...

So I'm assuming that most of us who mash in a cooler mash tun end up losing a couple degrees during the duration of the mash. If you have a target mash temp of 154, are you shooting to hit 154 at the beginning of of the mash ending a little bit lower or are you intentionally hitting high to eventually end up at 154 at the end of the mash?

For me, I've tried to hit a degree or so above my target mash temp and then settle to a degree or two lower than target by the end.

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Old 10-31-2009, 08:52 PM   #4
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In all reality, I think i'd answer my own question by trying to mash a few degrees higher in my next go around.

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Old 10-31-2009, 08:59 PM   #5
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What I do is preheat my cooler with hot water. I'll usually add the water at about 180 degrees, and then let it drop to my strike temperature. Then, it seems like I don't lose more than one degree over the course of the mash. Preheating the cooler for at least 15 minutes seems to make a huge difference!

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Old 10-31-2009, 09:07 PM   #6
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I have the same idea but use a little different method than Yooper. The bottomline, important point is that preheating the mash run makes a difference.

I loose very little (sometimes not even one degree) over an hour mash.

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Old 11-01-2009, 10:50 PM   #7
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So go figure... all three of the thermometers that I have are off! I have two floating thermometers and one lab thermometer... and they're all off by 1-3 degrees which had me mashing lower than expected. Before, I assumed that the lab thermometer was spot on and the other two floating thermometers that I had were within 1 degree of my lab thermometer which I was using as a reference. I checked all of them together last night with my cdn probe thermometer that I usually use for BBQ and found that they're off. Yes, it sucks that I have two extremely "dry" beers on tap now but I'm glad that I think I found the issue and will try to fix it on my next batches. I'll call one of them my saison IPA.

I just ordered one of those digital pocket KM12 deals so I'm hoping it's more accurate. Thanks for all of the info.

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