Always lower than expect FG

[Johntodd]

OK, I've got a few brews under my belt now. And I've had to let my belt out a little. </RIMSHOT>

My final gravity is always lower than expected. And the ABV is always higher than expected.

Not too worried about it, I'm making great tasting beer.

But I am curious as to what is going on. I'm following other peoples' extract recipes, and weighing things on a scale, etc. I'm also an experienced cook so I know how to follow a recipe; esp. an extract recipe.

So what gives?

Thanks!
-Johntodd

 

[CU_tony]

Im by no means an expert but are you hitting your desired OG every time? If you are hitting OG and then passing your FG it sounds like the yeast are doing to much work.
What is your fermentation setup like? Are you at the right temp for the yeast, and maintaining that temp during primary?

 

[GrogNerd]

I'd also look at fermentation temperatures

we like the yeast to be happy, but not TOO happy, so it's best to keep the temperatures towards the low end of the yeast's range

if you don't have temperature control, I HIGHLY RECOMMEND it. it provided an astonishing boost to the quality of my beers.

 

[Qhrumphf]

How far are you undershooting your FG? If you're hitting 1.014 instead of 1.016, there's probably no cause for concern. If you're hitting 1.006 instead of 1.016, then that may be another issue.

How are your recipes being modeled? Some sources are better than others. But any good software I can think of will still model a fairly standard fermentability of extract, which isn't the case. Some extracts are more fermentable than others (for example I believe Alexander's LME is slightly more fermentable than average, where Laglaander extracts are notoriously unfermentable). But if you're always using the same maltster's extract, then you should be fairly consistent. You may just be using an extract a little more fermentable than your recipe source assumes it will be. Problem with extract brewing is that you have no direct means of controlling that, unlike with all-grain where the mash temperature could be adjusted.

Of course fermentation temp is another possibility.

 

[Johntodd]

OK, could be temps, as I have absolutely no temp control. I also do not plan to; I'm on a "nature kick" of brewing ales in the heat and lagers in the winter.

Moments ago, I kegged two beers. Here are the numbers:

Witbier: OG: 1.100. (expected 1.069) FG: 1.010 (expected 1.016) ABV:11%
Oatmeal Stout: OG:1.044 (expected 1.049) FG: 1.006 (expected 1.011) ABV: 4.33%

Hope this helps!
Thanks all!

EDIT to say that I don't particularly care about "numbers", and I don't particularly care about being true-to-style. As long as the beer is nice and drinkable, me and SWMBO are happy.
But due to my inexperience, I don't want to set myself up for unforseen troubles down the line somewhere.

 

[Johntodd]

And my beer modeler is brewer's friend website.

 

[Biscuits]

I am wondering if when taking your OG if you are letting the sample cool to the appropriate temp for your hydrometer. I am thinking there is a devil in the details here because you would have needed some super yeast to attenuate 1.100 down to 1.010.

 

[chickypad]

Witbier: OG: 1.100. (expected 1.069) FG: 1.010 (expected 1.016) ABV:11%
Oatmeal Stout: OG:1.044 (expected 1.049) FG: 1.006 (expected 1.011) ABV: 4.33%

I am almost sure your witbier OG is an error measurement. You mentioned extract, if your volume is correct it's not really possible to miss your OG by much. Many folks doing extract with partial boil have erroneous measurements due to inadequate mixing, it's very tough to get it thoroughly mixed after topping off. Curious what your recipe was, 1.069 even sounds like a high target for a wit.

As someone else mentioned, be sure you are correcting for temp and also check the calibration on your hydrometer. I'm not sure fermenting warm would have anything to do with it - should mostly be related to how much unfermentables in your wort. You could certainly get stuck at a higher FG with an unhealthy fermentation but I don't think fermenting warm could make a wort suddenly more fermentable.

 

[CU_tony]

Warm doesn't make the wort more fermentable per se, but it will make the yeast more active and less likely to drop out of suspension until you get too high then yeasties die

 

[kh54s10]

I suspect the numbers for OG are off due to uneven mixing of top up water, incorrect volume or sampled at a temperature different than the Hydrometer's calibration. The OG of the Witbier is almost certainly not accurate.

FG could be off due to incorrect volume or the temperature of the sample.

 

[Johntodd]

Next brew I'll double check my mixing for topping off, but I don't think that's it. When I top off I take a sanitized whisk and whisk the batch for oxygen. It does get stirred. Will still check, though.

As for the Witbier style, I added sugar to give it more alcohol. We don't like to pee a lot, as someone's signature around here says. Not true to style.

As for the beast yeast, it was DanStar Nottingham on both beers. I had them ferment a previous brew from 1.110 down to 0.998. I used to make wine, so I've seen attenuation like that before. And, sure enough, that brew would knock your socks off. I ended up calling it "Colt 47".

My guess, based on your offerings, is temperature at the hydrometer. The wort always feels cool to touch, but who knows it's actual temp? That seems to likely culprit now.

Thanks!
-Johntodd

 

[boydster]

Since you are brewing extract, as long as you use the correct amount of extract and you have the correct volume going into the fermenter, your OG simply can't be wrong; you are mixing a known amount of sugar into a known amount of water. You stated that you are using top-up water - I'd bet dollars to donuts your wort was stratified with the syrupy wort on the bottom and the watery wort at the top. And I'd also bet you took your sample on the witbier from the bottom. It's pretty normal for all of this to happen, it's not a flaw in your process or anything, just something to keep in mind when you are taking your readings. With extract, trust what the recipe's target OG is (as long as you use the correct amount of extract and end up with the correct volume of wort) and trust your measured FG (since the yeast will have thoroughly mixed everything during fermentation).

As for why your beer is finishing so low, that's another question. Certainly temp could be the culprit. It could also be that there is another bug helping the fermentation along. For a beer to go from 1.110 to 0.998 with Nottingham is... shocking. I would suspect infection in that case. Unless I misunderstood what you meant.

 

[Johntodd]

IDK about infection ... wouldn't that make a noticeable flavor change?

 

[Qhrumphf]

Have you calibrated your hydrometer? I wonder if you're not reading a few points off acrosss the board.

Also if you're routinely dumping a bunch of sugar in your beers, that will drive the FG down.

 

[chickypad]

As for why your beer is finishing so low, that's another question. Certainly temp could be the culprit. It could also be that there is another bug helping the fermentation along. For a beer to go from 1.110 to 0.998 with Nottingham is... shocking. I would suspect infection in that case. Unless I misunderstood what you meant.

Agreed. Wine is one thing but not a malt based wort. Something is not adding up.

 

[Johntodd]

OK. I'll be brewing tomorrow. I'll check the hydrometer with plain water (and check the meter-temp charts) and also be sure to mix properly when topping up.

Thanks!