fermentations always stop early...

So my fermentation's always finish with their gravity a lot higher than they should be.... usually around 8-12ish points higher. I know a couple points are reasonable just depending on different variants but not the 8-12ish that I usually get.
The last batch I did was a scotch ale that the O.G. was 1.084 and FG was 1.032 (Suppose to be 1.022-24. I used safale us-05 and oxygenated for a minute with the disposable pure 02 and shook it another minute or two for good measure.
I ferment in a chest freezer with a temp controller monitoring temps. I have the thermometer taped to the side of the carboy with some cardboard and a bit of paper towels holding it against the carboy to hopefully measure more of the inside temp of the carboy.... I'm pretty sure it's right there with what the beer temp is.
The last batch I did I was wondering if it was due to the carboy sitting against the bottom of the chest freezer and getting too cold too quickly and "giving a shot of sleepping pills" to the yeast to make them go dormant too early as it is getting closer to being done. So, I cut a few 2x4s in ft long sections and stored the carboy on top of these boards. Not much luck....
I'm getting annoying and not sure how else to try and figure this out. Spent money on the temp controller and chest freezer and now not sure if it's really helping much more than just a water bath in my bathroom!

Any suggestions?

Thanks!!

How are your pitching rates? Are you making any starters or rehydrating?

Check out Mr. Malty to find proper pitching rates for specific yeasts. http://www.mrmalty.com/calc/calc.html

Ultimately though, how does your beer taste?

Follow mrmalty all the time. Rehydrating since more of the times I use the dry yeast but if I do use the others I do use starters.
Beer tastes good but some is a bit too sweet and not dry enough and you can tell it wasn't finished doing it's thing

How are you measuring gravity?

my hydrometer.. It is off by a few points but I take that into consideration when I check it.

Are your OG's off as well?
Is your hydrometer reading 1.000 in pure water?
Are you reading at the calibrated temperature?

What temperature are you holding for the fermentation?

Most of my O.G.s are right on... unless I do something wrong obviously.. but otherwise no, they are correct.

Hydrometer reads 1.004 in pure water at 68. So when I do my reading I just subtract .004 from it.

depending on the yeast,.. I used to keep the temp monitor at a specific setting, for instance 65 or 66 and just leave it... lately, I have been setting at say 65 for the first 1-2 days of fermentation then up to around 67-68 for last few days in an effort to not put the yeasts to sleep early.... but that hasn't seemed to help either.

What about recipes? Are these all-grain? Is your mash temp off?

How are you aerating? Even if you pitch right if there is no oxygen you will have trouble hitting your FG. I had a batch finish high a few months ago because I was too lazy to aerate properly, even though I did a starter.

pabloj13 said:

What about recipes? Are these all-grain? Is your mash temp off?

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Good call re recipes. I have heard a lot of comments about LME being less predictable in fermentation and less likely to achieve FG. I don't have enough experience to comment, but I have read it a lot.

freisste said:

Good call re recipes. I have heard a lot of comments about LME being less predictable in fermentation and less likely to achieve FG. I don't have enough experience to comment, but I have read it a lot.

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Yes this is true but more like 1.020, not in the .30's

Are you sure you temperatures are correct and calibrated? If fermentation is too cold the yeast will quit on you.

You might want to try removing the primary from the chamber after active fermentation and let warm up a bit and gently rouse the yeast and see if you can get those last points.

In addition, are you going to secondary? If so, you need to verify FG first, if you are removing the beer off the yeast too soon the yeast may not fully attenuate as well.

Yes, all grain. Mash temps are correct. I aerate with pure 02, the disposable kind and an aerating stone thing from Morebeer.com for about a minute and then shake it up.

When in doubt, try a forced-ferment test. On your next batch, take a quart of your wort, plenty of yeast, and lots of o2 and ferment it at room temperature (70+) as if it were a starter (a stir plate is best). When it is finished, measure the gravity of that sample.

If your forced ferment test finished much lower than your whole batch, then you have a fermentation problem (not enough yeast/02, bad temps, etc).

If your forced ferment test finishes about the same as your whole batch, then you have a hot-side problem (recipe, mash temp, etc.).

Alright, will have to try that and see. Brewing another batch next week so I'll see what I come up with with the tester. Thanks!

freisste said:

Good call re recipes. I have heard a lot of comments about LME being less predictable in fermentation and less likely to achieve FG. I don't have enough experience to comment, but I have read it a lot.

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My first 3 brews were LME and they all finished below what I expected except for an imperial stout I did before I knew I needed a starter for bigger beers. That stopped way short. I also brew 3 gallon batches so a smack pack is the perfect size for my fermentations.

JDFlow said:

My first 3 brews were LME and they all finished below what I expected except for an imperial stout I did before I knew I needed a starter for bigger beers. That stopped way short. I also brew 3 gallon batches so a smack pack is the perfect size for my fermentations.

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Have you verified a smack pack alone is adequate by using a calculator? Not only is the batch size important but also the gravity and date on the pack which will reflect viability of yeast. You might be surprised to learn that you are still under pitching

What would be the harm in just pitching a gram or two more yeast? If it tastes sweet, shouldn't the new yeast just continue where the old ones left off?

jwalk4 said:

What would be the harm in just pitching a gram or two more yeast? If it tastes sweet, shouldn't the new yeast just continue where the old ones left off?

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If the cause of the problem was less fermentable wort than no, additional yeast will not just finish it up. In addition you would no be pitching yeast into an alcohol environment which would cause them to stress out. Some people would recommend adding champagne yeast or a small starter at full krausen to combat this although results will vary.

Matteo57 said:

Yes, all grain. Mash temps are correct. I aerate with pure 02, the disposable kind and an aerating stone thing from Morebeer.com for about a minute and then shake it up.

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I just changed from an Igloo MT to a direct fired MT and a couple of my batches mashed too high while I was dialing in the system. One of them stopped 10 pts short of estimated FG while the other was 8 pts short.

Mash temps was my first thought actually. It would explain the consistency of your results better then pretty much anything else. Are you using campden by any chance? When and how much?

duboman said:

If the cause of the problem was less fermentable wort than no, additional yeast will not just finish it up. In addition you would no be pitching yeast into an alcohol environment which would cause them to stress out. Some people would recommend adding champagne yeast or a small starter at full krausen to combat this although results will vary.

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Thanks for the info!

Not using camden tablets.
When I dough in I check temps for a good few minutes while stirring and making sure no dough balls or anything and all is stirred together well. I will then usuallly check it at least another 1-3 times throughout the process. My igloo usually keeps it within 1 degree or so for the duration, it works great!

Matteo57 said:

Not using camden tablets.
When I dough in I check temps for a good few minutes while stirring and making sure no dough balls or anything and all is stirred together well. I will then usuallly check it at least another 1-3 times throughout the process. My igloo usually keeps it within 1 degree or so for the duration, it works great!

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But could something be wrong with your thermometer? Have you calibrated it?

Extract or all grain? If you're actually mashing, calibrate your thermometer and mash lower, say 150.

If extract, try subbing some corn sugar for extract. Also when you ramp up the temp on fermentation, give your fermentor a good shake to get the yeast into suspension, also you can take the temp up to 70+ with no worries.

Eta : missed the post two up. Try mashing lower. Also a large amount of specialty malts will increase your unfermentables.nix the carapils if you use it and add simple sugars.