Consistenly High FG

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guinnessface

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(Damn, I just saw I spelled "consistently" wrong in the title).

I'm a little stumped here, I'll defer to the experts on this. My last three AG batches have finished with uncharacteristically high FG. I'm pretty experienced and haven't run into this problem before. All 3 were in the 1.05 to 1.06 OG range and finished around 1.04-1.06. Here's what the conditions were (All were mashed around 154-156 degrees):

Beer 1: Coffee Porter. This had lactose, so I expected the high FG, but there were still more to ferment out at the end.
Beer 2: Double IPA. This finished around 9%, but I used honey for a cleaner finish, it's still pretty cloying. For this and the porter, I used Cal Ale yeast and fermented around 68-72 degrees.
Beer 3: Hefeweizen: I used a Hefe Ale yeast and same fermentation conditions...it only went from a 1.054 to a 1.014 after 3 weeks and re-agitation...it initially had a very active start. Plus the finished product is more tart than I expected. In the past, the FG on this recipe usually ends up right around 1.01.

So with the 1st 2, I used starters and let things go for about 3 -4 weeks in a conical. I'm pretty sure I even re=pitched some more yeast in the porter, so it leads me to believe it's a mash problem rather than a fermentation problem.

I hit my strike temps in a cooler, spot on, then leave it for about an hour. Will the dropping temp cause a rise in unfermentable sugars? It hasn't been a problem in the past. I usually heat the sparge water up to 180 and even that only brings the mash up to the upper 150's....maybe the conversion is going on too long? I wonder if a mash out after 45 minutes would help instead.

I've double checked other things like m thermometer and equipment; everything is calibrated properly. The only remaining thoughts I have is that maybe the temperature change is affecting the beer (at the top of a finished basement stairwell, next to the kitchen). Maybe the swings in temp from the oven and cold from the basement have an effect, though they haven't in the past!

I'm at a loss here. I've tried to look at this from several angles and keep coming up short. Any thoughts you might have would be greatly appreciated.

All the best, and cheers!

guinnessface
 
Actually dropping temps and longer mashes would make the wort MORE fermentable, not less.

Just so I'm understanding, the first two went (best case) 1.060 to 1.040? There's definitely something wrong there.

  • Are you getting complete mash conversion? Unconverted starches won't be fermentable by yeast.
  • How sure are you on the thermometer temp? Have you changed thermometers?
  • Are you reading FG by a refractometer or hydrometer?
  • Have there been any other equipment changes or process changes between the previous batches and these three?
 
Thanks for your reply. I had a typo there, it was 1.014 vice 1.04. I haven't checked the ph in the mash in a while, but have had pretty reliable results with complete fermentation otherwise. I used a digital thermometer twice, but went back to my lab thermometer for this last one. I've taken my readings with a hydrometer and have had no real equipment or method changes from mash to kegging. That's what's so confusing!
 
Ok, then it sounds like it's just you're mashing a little warm for what you want. Those FGs are very reasonable for those mash temps and original gravities, even figuring some higher attenuating yeasts. If you're using lower attenuating (English or English-derived American) yeasts for the Porter or IPA, you actually got very good fermentability, espeically if lactose is involved.

You may not have a thermometer as accurate as you think you do (many thermometers have a wide temperature tolerance of a couple degrees, more than enough to cause changes in fermentability). And if you're mashing as high as 156, and still getting ~70% attenuation, that's nothing entirely out of the ordinary. In fact, you may be getting higher attenuation than I'd normally anticipate. I actually follow that kind of mash schedule regularly looking to get the results you're getting, but starting at a lower gravity (aiming for 1.014-1.015 starting from 1.040-1.045 or, or even my house beers at 158 that go from 1.033 to 1.012 or so).

If you want the FG to drop a few points, drop the mash temp down to 152 or so. 152 is a pretty good middle of the road mash temp. 156 is definitely on the hot, alpha-amylase heavy side (although by no means extreme, I've gone to 160 and others have gone higher).
 
Great advice, thanks a million. I'll double check the thermometer and try dropping the mash temp a bit.
 
Great advice, thanks a million. I'll double check the thermometer and try dropping the mash temp a bit.

You'd have to look at the specs for the thermometer. Many (including digital) will offer a precise reading (say, 154.2), but will have an accuracy of +/- 2 degrees or more. No point in having that 0.2 at all if the actual temp could be 156.2 or 152.2. And the kicker is, just because it's accurate at one temp doesn't mean it'll be accurate at another. A thermometer can easily read 32F in ice water and 212 in boiling at 1 atm (or whatever it's supposed to at a given elevation), and still read 152 when it's actually 154-156. I had that problem routinely the opposite way, I thought I was mashing in at 154, but was really at 149, because the +/- 5 degrees of the thermometer went that way at mash range- it was almost dead on at both freezing and and actually read the other way, a degree or two low, at boiling. All my mashes attenuated far more than I wanted unless I intentioanlly mashed high. Needless to say, I ended up switching to a high quality thermometer (Thermapen, which is +/- 0.7 degrees) and my results are much more predictable as a result.
 
I'll double check my usual thermometer. It's been pretty good compared to the digital which was consistently several degrees off. Thanks for the advice
 
Thermapen are having a sale on Teal at the moment. Got an email yesterday. It seems they are always having some color on sale for $79. I got green for Paddy's day sale.

A great product. Use it for everything brewing and cooking related.
 
Sometimes you can get them even cheaper than that. But many brewers (myself included) swear by the Thermapen. It's expensive, but it's one of the best out there, plain and simple.
 
@thwemerkle: I have an aerated transfer tube that usually helps add some O2 in from kettle to fermenter once it's cooled. It hasn't been a typical problem
In the past. Good point though, it's often overlooked. Thanks
 
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