Help with consistent high FG problem

Okay, so I recently got back into brewing after a long time off. So far I've done 8 batches and all have had a problem with high final gravities. I think I've addressed all the obvious things - I double checked the hydrometer and thermometer, started mashing lower (around 148-150), pitch larger volumes of yeast, aerate more thoroughly, leave the beers longer in the primary, etc.

For example, my latest batch is a bitter (5 gal) with an OG of 1.040 from a base Marris Otter with .5# 50L crystal and that's it. I aerated with a pump and airstone for 30 min, pitched the yeast (Wyeast 1450) from a 2L starter at 65F. Fermentation took of right away - ambient temp in the basement is 60F (air temp) so I'm guessing the ferment temp was mid 60s. After 4 days a sample was at 1.030, so I roused the yeast and moved upstairs (ambients temp 70F). It's been there for a week, and samples the last three days have been steady at 1.024. That's less than 50% attenuation.

The other batched have been similar, but some have used a pack or two of dry yeast (some Notty, mostly S-05) and others have been directly on the yeast cake of an earlier batch. The resulting beers have, surprisingly to me, been drinkable - nothing all that sweet, no off flavors, etc.

Any ideas what might be going on here? I know my fermentation temps have been on the low side, but they seem to get going fine and I generally bring them upstairs where it's warmer once it slows down. The only other consistent thing is the aeration system, but shouldn't even terrible aeration should do better that 1.040->1.024 (with a big starter)? And pitching a lot of dry yeast did similarly, and as I understand it they're less sensitive to aeration.

Maybe I'm really messing up the mash - if I'm producing a ton of unfermentables then the yeast are doing the best they can and no amount of pick volume, aeration, etc will fix it. That would also explain why the don't taste sweet. But I don't understand what I could be doing wrong - I've been paying close attention to the mash temp the last few batches, and to be safe I've been letting them go 90+ minutes. I'll do a conversion test next time, but I have a hard time believing that's the problem - how could that happen so consistently across several batches if the thermometer is fine? My water is Great Lakes water from the Chicago municipal system, treated with campden, and the last few batches have used 5.2 ph stabilizer in the mash just in case. Some of the mashes have had some gypsum as well, but certainly not all.

Any other ideas?

It certainly sounds like you've covered most of the obvious things.

The first thing I would suspect is the thermometer. How did you calibrate it?
I assume you calibrated the hydrometer with water and are doing the temperature corrections.

Next, I would look at using a water bath with an aquarium heater to get your fermentations into the desired range. All of my fermentations improved after I switched from ambient to a water bath. The heater allows you to dial in a temp, and the thermal mass of the water helps slow down temp changes. Plus you don't have to cart the fermenters upstairs

You mentioned the aquarium pump/aeration system as being a potential problem. I'm suspicious of that as well. Next batch, just put the carboy in your lap, cover it with a piece of sanitized tin foil and shake the bejeezes out of it, and see if you can't get better attenuation. I mean really, when you think about it the only things it could possibly be are:

1. Incorrectly calibrated thermometer/hydrometer (Check thermometer with a cup of ice water and boiling water. Check hydro with distilled water at 60* F)

2. Improper pitching temperature into wort or starter wort (Re-calibrate thermometer)

3. Old or mishandled yeast (Try a new lhbs or order from another online vendor)

4. Gravity of starter too high/low
( http://brew.stderr.net/starter_wort_calc.html )

5. Lack of oxygen (Try shaking vigorously)

6. Large fluctuations in temperature during ferment (Or even small fluctuations with some of the more floculent yeast strains)

bgough said:

You mentioned the aquarium pump/aeration system as being a potential problem. I'm suspicious of that as well. Next batch, just put the carboy in your lap, cover it with a piece of sanitized tin foil and shake the bejeezes out of it, and see if you can't get better attenuation. I mean really, when you think about it the only things it could possibly be are:

Thanks for the reply. I have been shaking and pouring bucket-to-bucket as well, but I can make sure I do more to see if that helps. I like your list of ideas, but wonder how much each one might matter:

1. Incorrectly calibrated thermometer/hydrometer (Check thermometer with a cup of ice water and boiling water. Check hydro with distilled water at 60* F)

I have checked it with tap water, the DME/water mix for starters, and the OG of my batches against the expected with average efficiency. None of these is very accurate, but since they all check out I can't believe it's off by more than 5% or so - which doesn't come close to explaining final gravities of 1.020-1.030 from regular strength beers with simple malt bills.

2. Improper pitching temperature into wort or starter wort (Re-calibrate thermometer)

This might be a real issue - I've used a few thermometers and checked them at boiling/freezing to know they're accurate to a reasonable margin, but for chilling for pitching I know the wort at the top and bottom of the boil kettle are at very different temps and I don't mix that thoroughly at the end to keep the trub/hop debris/etc settled. On the other hand, even if I'm pitching at 85 or 50 when I think it's 65 can it be that serious? Given that the ferments are taking off ok, I'm not killing them, and ambient of 60-65 should get it to something reasonable within a day or so (while I'm still seeing obvious active fermentation).

3. Old or mishandled yeast (Try a new lhbs or order from another online vendor)

I'd believe this, but I've used several yeasts from a few sources, so it doesn't seem likely unless the one mishandling them is me - but how badly can you screw up keeping packets of dry yeast in an airtight bag in the fridge?

4. Gravity of starter too high/low
( http://brew.stderr.net/starter_wort_calc.html )

Unless the hydrometer is really off this isn't it - and even if it is, that doesn't explain the dry yeast without starters behaving the same.

5. Lack of oxygen (Try shaking vigorously)

This is still my guess, but so many people report much better success with dry yeast and no aeration at all, I'm not sure this could be the complete explanation either.

6. Large fluctuations in temperature during ferment (Or even small fluctuations with some of the more floculent yeast strains)

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I don't think the basement varies so much, and I have not been seeing signs of early flocculation. I have been trying bringing the fermenter to warmer temps and swirling to re-suspend the yeast - wouldn't that work?


Given how consistent it has been with a large range of recipes/yeast/suppliers/techniques I think it has to be either something in the mash/sparge that's producing worts of the right OG that just aren't fermentable or something in the yeast handling somewhere along the way that is knocking the out really early.

So, for the next batch later this week I have two ideas - check for conversion (will that detect unfermentenables or just unconverted starch?) and to aerate by hand sufficiently to rule that out. Anything else that might explain it? If these steps don't work, what should I try next?

Here are other things you should look into.

If you hydrometer is dirty or has glass surface defects, those provide nucleation sites for dissolved co2 which post fermented beer is loaded with. If your hydrometer is incorrectly calibrated, your OG would be off as well but you haven't mentionned anything about that so I assume those readings are what you're expecting. Try vigorously spinning the hydrometer to shake such bubbles off before making a reading.

If the above doesn't work you may want to try an extract beer to see if he mashing is the cause of the issue. Although if your thermometer is fine, I can't imagine that being the issue with the temperature you're mashing at.

Lastly, you should also double check the freshness of your grain. The enzymatic content of stale grain may be insufficient to convert. Keep in mind this is rarely an issue especially if you buy grain frequently. Beyond these other things to consider, I have no idea what else could be responsible.

I think you've got it, if your beer is not sweet tasting, then it's not a yeast attenuation problem.

It sounds like a bad hydrometer or bad thermometer.

kwhyte said:

Anything else that might explain it? If these steps don't work, what should I try next?

Click to expand...

I’ve been having the same problems as you. Almost the exact same problems, in fact. My beers always finish 3-4, sometimes as much as 8 points higher than I expect/hope they will. 75% attenuation is place I’ve not yet been, and 60-65% is sadly routine.

And I never had the problem when I was extract brewing without using a starter. I switched to AG, managed to hit all of my OGs, took care to pitch more yeast, and suddenly I can’t ferment out. So I’ve concluded it must be something I’m doing wrong with the mash, yet my thermometers have been tested and confirm I’m right in the area of 150 each and every time.

What I’m considering, and just recently tried to account for, is the design of my MLT, which is 10g stainless steel, with a space of 1.5 gallons under the false bottom. Previously, I’d heat my strike water in the tun, and when it landed where I wanted (about 11 degrees above target mash temp), I’d stir in the grain - thoroughly. My dial therm would tell me I’m right on, as would my digital probe when poked into various spots of the mash surface. My theory is that those 1.5 gallons of 160+ degree water sitting on heated steel below the false bottom have been screwing with my mash temps. Sure, on the surface, and halfway down the grainbed, temps read right. But down there near the FB, there’s extra heat biding its time, waiting to make unfermentables of any starches that come near it. Could be? I mean, it’s got to be SOMETHING!

So, with this last batch, I stirred my strike water without the false bottom in place, to ensure uniformity. Then put back the false bottom, then added grain and stirred. THEN, recirculated at least a gallon to move the hot water under the FB back around, and stirred thoroughly. My dial therm told me 149, as did my digital probe, and the dial dropped to 147 by the end of a 70 min mash. I’m praying I have solved the problem. This is supposed to be a tripel, and I want to see a FG no greater than 1.010.

So, if you’re using something like the same gear I am, maybe this was helpful.

If you’re not, I humbly apologize for boring you into a coma.

I appreciate the suggestion - I think it is clear something is wrong with my mashing. I'm pretty sure it's not the hydrometer, so I think it must either be a temperature thing or something relating to water chemistry. Can anyone recommend a thermometer that responds quickly and accurately and can take submersion in boiling wort?

Judochop said:

I’ve been having the same problems as you. Almost the exact same problems, in fact. My beers always finish 3-4, sometimes as much as 8 points higher than I expect/hope they will. 75% attenuation is place I’ve not yet been, and 60-65% is sadly routine.

And I never had the problem when I was extract brewing without using a starter. I switched to AG, managed to hit all of my OGs, took care to pitch more yeast, and suddenly I can’t ferment out. So I’ve concluded it must be something I’m doing wrong with the mash, yet my thermometers have been tested and confirm I’m right in the area of 150 each and every time.

What I’m considering, and just recently tried to account for, is the design of my MLT, which is 10g stainless steel, with a space of 1.5 gallons under the false bottom. Previously, I’d heat my strike water in the tun, and when it landed where I wanted (about 11 degrees above target mash temp), I’d stir in the grain - thoroughly. My dial therm would tell me I’m right on, as would my digital probe when poked into various spots of the mash surface. My theory is that those 1.5 gallons of 160+ degree water sitting on heated steel below the false bottom have been screwing with my mash temps. Sure, on the surface, and halfway down the grainbed, temps read right. But down there near the FB, there’s extra heat biding its time, waiting to make unfermentables of any starches that come near it. Could be? I mean, it’s got to be SOMETHING!

So, with this last batch, I stirred my strike water without the false bottom in place, to ensure uniformity. Then put back the false bottom, then added grain and stirred. THEN, recirculated at least a gallon to move the hot water under the FB back around, and stirred thoroughly. My dial therm told me 149, as did my digital probe, and the dial dropped to 147 by the end of a 70 min mash. I’m praying I have solved the problem. This is supposed to be a tripel, and I want to see a FG no greater than 1.010.

So, if you’re using something like the same gear I am, maybe this was helpful.

If you’re not, I humbly apologize for boring you into a coma.

Click to expand...

I'm using Lake Michigan water as well (Lake County), and nearly every homebrewer I've talked to here uses the same water without treatment. Even if your water wasn't ideal, I'm not sure how wacked it would have to be to affect attenuation, if that could do it at all. Bottom line, I don't think it's a matter of water chemistry, for whatever that's worth.

Meeting OG and failing to meet FG is either a yeast issue, or an unfermentables issue, (or a cruel hydrometer issue). You've done what you can to treat your yeast well, as I had. You tested your hydrometer, as I had. It really sounds to me like a matter of unfermentables.

What are your exact mash procedures?

Judochop said:

I'm using Lake Michigan water as well (Lake County), and nearly every homebrewer I've talked to here uses the same water without treatment. Even if your water wasn't ideal, I'm not sure how wacked it would have to be to affect attenuation, if that could do it at all. Bottom line, I don't think it's a matter of water chemistry, for whatever that's worth.

Meeting OG and failing to meet FG is either a yeast issue, or an unfermentables issue, (or a cruel hydrometer issue). You've done what you can to treat your yeast well, as I had. You tested your hydrometer, as I had. It really sounds to me like a matter of unfermentables.

What are your exact mash procedures?

Click to expand...

Looking back over my process I think there are a few places where I could be going wrong. I use a rubbermaid cooler mash tun. My procedure is to heat water in by brew kettle until it reaches strike temps (calculated by brew software, usually around 15 degrees above my planned mash temp). While that's heating I put 1-2 gallons of hot tap water in the cooler (together with my pitcher) and close it to warm up.

When the strike water hits temp, I dump the water from the cooler and use the pitcher to transfer. I alternate water and grain, mixing as I go to avoid dry clumps. Once everything is in I stir a bit more, check the temp in a few places, and close it. While this is going on the remaining water is heating further, I usually just let it get to boiling and then turn it off. After that I just wait 60-90 minutes, sometimes longer (this is a step where I often have to do other things - cook dinner, put the kids to bed, etc.).

To sparge I turn the heat back on the kettle to heat the remaining water for sparging. I'm not that careful about the temps here, I just aim for 170-180 or so. When I get there, the first batch volume goes in, everything gets stirred and then is allowed to settle for a few minutes. I then drain off the wort, recirculating until it is running clear. Once that's drained I repeat with the second volume of water and that's it.

Maybe I'm doing something really wrong in here somewhere? I've never actually brewed with anyone else except for some extract batches awhile ago, so it's possible I've just badly misunderstood how it should work - but it seems fairly straightforward. If the process sounds ok I think there are a few points where I can be more careful :

- I usually can't get a very good reading of the mash temps because the thermometer I have can only read temps at the surface, and I don't think the temps are really that uniform at the start. So I'm really trusting the process and strike temp to get me where I should be. I'm looking for a thermometer that can read temps are various depths to get better at this, but so far haven't found anything that responds quickly and can be submersed in a foot or two of mash. How do other people measure mash temps?

- I'm not sure my volumes are that accurate either. I know how much the pitcher holds and use that to measure the amount of water for each addition, but what "full" is for the pitcher is a bit subjective, so I could be off by 10% or something. I imagine that would make the temps off a little, but playing with the software it doesn't seem like it'd make a difference of more than a degree or two.

Overall I can easily see how I could be off by several degrees (software doesn't match my equipment, volumes off a bit, etc.) but not where much bigger errors would come from. I've always figured that if I aim for 152 or so, even if I'm off by 5 degrees either way it should still convert fine - is that not true? It's hard for me to think I'd be off by much more than that unless my thermometer is suspect. I have checked it against others around the house and it seems ok, but I'm going to try to get a better one and see if that helps.

Well, it all sounds right to me. Strike water 15 degrees over mash temp is a little higher than what I find works, but it's not outrageous. I know that mash temps play a very important role in determining final gravity, but I guess I don't know just to what extent. For example, if you're mashing at the higher end of the typical range, say @ 158, I really don't think you should expect an attenuation drastically different than what the manufacturer's range predicts (provided your yeast count and O2 levels are adequate, which they seem to be). Those attenuation ranges they give take into account reasonably high levels of specialty grains and reasonably high mash temps. I'd think you'd have to exceed a mash temp of 160 before you started to see attenuation suffering well below the expected ranges.

Mithion's idea of going to an extract brew just once isn't a bad one. Hard for me to give that advice, since I'm in the same predicament as you and haven't tried that approach, but it might give you some peace of mind, I think. If you brew w/ extract, and all other things are kept equal in your process, and you end up with a decent attenuation, then you KNOW it's the mash and you can focus your attack. If my tripel currently fermenting doesn't turn out with a decent attn, after I've applied every precaution I can think of, I may very well do the same.

Good luck! I'll probably keep checking in here to see if anyone else has advise for you that I can steal!

I have been making starters with DME and they have been fermenting fine, even the second one when I need to step up to a big starter. Really, how badly can you mess up an extract batch unless you pitch at a temp that kills the yeast? That's part of what convinces me that it must be the mash - after all, people make extract beer with no aeration at all and wildly fluctuating fermentation temps and still get reasonable attenuation (plus a ton of off flavors, but that's a different story). Based on my notes, the runnings from the mash weren't even that sweet even with right right OG. I don't know if I think the temps are too low and I'm not getting conversion or if they're too high and and I'm denaturing the enzymes (or at least some) with much the same result. It's also possible I'm just getting bad/stale grain - it has basically all been from midwest supply and they have a good enough rep and fast enough turnover that I doubt that's it. I'm really hoping that a better thermometer and more careful measurements all around will take care of it. I'll report back either way.

https://www.homebrewtalk.com/wiki/index.php/Iodine_test

This should help you find out if you have good conversion. I just use iodophor. get a drop on a toothpick or something.

Wandering about the forums in search of another topic, I came across some information which might be of use to the OP as well as me.

As I said earlier, I’m frustrated by the fact that since I’ve switched from extract to AG, my final gravities have gone up, yet all I’ve changed is doing my own mash and using yeast started. Assuming that adding more yeast cannot possibly be problem, I assumed it was my mash temps.

But perhaps that is not all I’ve changed in the switch. I just read somewhere that by adding tap water to top off a primary to 5 gallons after an extract brew, I was actually adding O2 which was present in the water. Whereas in AG brewing, I boil away all that O2. It never occurred…

So, while my aeration techniques were constant, my levels of oxygenation have probably not been. Maybe it wasn’t the mash’s fault after all? I feel bad. I’ve really been down on my mash tun, yelling at it, calling it a liar and a bast#$% and worse.

I just tried O2 injection for the first time with this last batch, along with absolutely positively ensuring the accuracy of my mash temps, so hopefully the problem is licked. You may want to consider O2 as well, kwhyte.

FWIW, I did something right this time. I just took a gravity reading on my tripel, coming up on the 5th day of fermentation this evening, and she's down at 1.011. And, though airlock activity has slowed to a crawl, it's still burping once every 30-45 seconds or so, so she may go lower yet.

This is the first FG I've met since AG'ing. The only things i did differently, are to ensure uniformity in my mash (so I KNOW 149 really means 149) and inject O2 (as opposed to siphon spray and shake). I guess I'd like to think I clevery solved a problem with a sneaky mash tun, but I have this gnawing suspicion that it's always been simply a matter of getting more O2 in there.

So, kwhyte. If you're still out there, try getting a stone and some O2 and see if that doesn't wake your yeasts up.