final gravity question

[Ken_CT]

How close should I expect to get to the recipe's final gravity?

I have a Nut Brown ale in the secondary which has a designed final gravity of 1.013. I'm currently at 1.017 and it hasn't moved for over a few days (multiple readings at 64F). The OG was pretty much spot on. I plan to bottle tonight, but was wondering how common it is to be a bit off on FG if the OG was correct.

 

[Aleforge]

Was it an extract?

If the gravity readings are steady over multiple measures then its done, if its extract its normal. Extract has a habit of not nailing its projected gravity.

 

[jcarson83]

How long has it been fermenting?

 

[Ken_CT]

yep, it was dried extract with specialty grains recipe.

Is there a range I can expect (.005 off for example) before worrying if I've got a stuck fermentation?

 

[Ken_CT]

How long has it been fermenting?

it was in the primary for 8 days, has been in the secondary for 16 days

 

[jcarson83]

My guess is its done but it won't hurt to let it sit for a week or so.

 

[Bob]

What was the OG? What yeast did you use?

The process of fermenting from OG to FG is called "attenuation". Each strain of yeast has its own range of attenuation percentages. That can make for a wide range of FGs from the same OG.

For example, Wyeast 1056 - a popular American ale yeast - has an attenuation range of 73-77%. This means that, given an OG of 1.048, the FG could be anywhere from 1.013 (73%) to 1.011 (77%). Alternately, Wyeast 1187 (Ringwood Ale) has an attenuation range of 68-72%. Given the same OG, the FG could be anywhere from 1.016 to 1.014.

Please keep in mind these ranges are under optimum conditions, which homebrewers - even the most advanced - rarely achieve. There are many factors that influence attenuation. Temperature, wort aeration, composition of wort sugars, blah blah blah. That's why it's important you pay attention to the following sentence, which I want you to write five hundred times on the chalkboard:

A piece of paper cannot control my ferment.

You see, yeast can't read. They don't know the piece of paper says they should ferment another degree Plato. Hell, you can read it out loud to them and still nothing would happen, because they also don't understand human speech. They have one word, and it sounds like "bloop". (Remarkably, we hear it translated through the airlock. Fascinating.) They only understand their environment - what's there to eat, the general 'livability' of their environment, etc.

The only way we can tell if they've finished the job is to use a scientific instrument to gauge progress. That's your hydrometer. If the reading is the same three samples in a row, and the reading is within the yeast manufacturer's stated attenuation range for the yeast, you can rest assured the yeast have done their job and the ferment is complete. If the samples are the same and the reading is well out of that range - high - then you have some thinking to do. Is the reading too high? Using the above example, if the FG reading is 1.018, I'd suspect the yeast are not finished; they're on strike.

But that's for another thread. In future, ignore the FG on the piece of paper. There are too many variables involved for that number to be useful.

In this specific instance, 1.017 may very well indicate a complete ferment. But until you tell us what recipe, and yeast you used, I can't make a definitive judgement.

Cheers,

Bob

 

[Ken_CT]

thx for the detailed response. I'll post the recipe and yeast strain used when I get home

lol at the yeast can't read comment.

 

[Bob]

Thought that might get a giggle.

I'm off-line from tonight (10PM?) through Monday AM, so if I don't get back to you right away, hit me with a PM to remind me of the thread.

Bob

 

[Aleforge]

I enjoyed that NQ3X, some reason halfway through I started thinking it came from monty python.

 

[Bob]

I live but to serve. I read far too much (or not enough) Terry Pratchett and PG Wodehouse.

 

[Ken_CT]

Thanks Bob

here's the recipe:

OG 1.053 FG 1.013 SRM 24 IBU 28 ABV 5%

specialty grains:
5oz British 55L Crystal malt
3oz British Chocolate malt

6 lbs. Muntons Extra Light Dry Malt Extract
5 HBU East Kent Goldings (bittering)
2.5 HBU Fuggles (bittering)
0.5 oz East Kent Goldings (flavor)
1 tsp Irish Moss

pitched with Wyeast 1187 Ringwood Ale.

I was a bit worried about the fermentation temp as it dropped to 58 for a couple of days. Testing the samples they don't taste sweet if that matters any.

 

[Ken_CT]

wanted to give a quick update. I swirled my beer a bit to re-suspend the yeast, and after a couple of days have now reached a gravity of 1.012 (checked over two days) So I guess it was a bit stuck and got moving again.

 

[Bob]

Aha! There's the thing - Ringwood. Ringwood is a tricksy little beastie that takes a lot of getting used to. It's not a yeast I recommend to a new(er) brewer, as it requires a bit of specialized technique to successfully use.

Ringwood specifies a range of 68-72% attenuation. 1.017 from 1.053 is 68%. If what I suspect about your procedure is true - underpitching, combined with your cold ferment - that FG is a reasonable one.

Bob

 

[Ken_CT]

Hey Bob,

yes your suspicions are correct. I pitched only one smackpack. (smacked about 4 hours before pitching). I'm learning about starters and will use one next time. Temps of the fermenter have been right on the edge of 60. We're expecting some warmer weather later this week which should help. I bottled that batch at 1.012 last night, and now have a Bavarian Hefeweizen fermenting.

thx again for your help!