how close is "close enough" for attenuation?

[redfox]

I *DO* understand taking FG readings several days apart to confirm fermentation is done (and I WILL do so!).

just curious re: apparent attenuation, versus published data for that yeast, etc...

so, I have a nut brown ale (OG = 1.072). just checked the gravity and it's at 1.021. Safeale 05.
[extract, steeping grains, and a bit of beet sugar]

an on-line calculator says I'm around 71 percent apparent, but the published data says it should be about 81 percent...

 

[smata67]

How long ago did you pitch? I bottle at 3 weeks after pitching and it has mostly worked out. 1.021 is not bad for a higher gravity beer using extract. And 71% is acceptable. The "published data" is optimistic. I don't think I have EVER gotten 81% with S05. If you do a 1.040 or so beer, maybe. But not anything realistic over 1.060.

 

[redfox]

Thanks for the reply. after the bubbles in the sample settled, I re-read the hydrometer...it's 1.025

new numbers come in at 65 percent apparent.

Pitched just over a week ago. was hoping to bottle this weekend, if it stays the same.

 

[RM-MN]

Thanks for the reply. after the bubbles in the sample settled, I re-read the hydrometer...it's 1.025

new numbers come in at 65 percent apparent.

Pitched just over a week ago. was hoping to bottle this weekend, if it stays the same.

There a number of factors that determine the attenuation of the yeast. Part of that is the makeup of the wort as it probably contains some unfermentable sugars. Part of that is the temperature regime as too cool and the yeast quit early, too warm and they overattenuate and throw esters and fusels. Part of that is pitch rate and part is how you prepare the wort for the yeast's propagation. Part of it is time. You're just over a week. With the right combinations of conbination of factors the beer should be done but we don't know what the combination is in your beer.

Things you can try include warming the beer (low to mid 70's help if the beer was fermented cool), swirling the fermenter to resuspend some yeast, and adding a simple sugar to get the yeast restarted.

 

[Qhrumphf]

Reading with a hydrometer, not a refractometer, correct?

Extracts are notorious for underattenuating. To the point that it often limits around that point.

I haven't used US05 in a very long time, but with another Chico variant (from a smaller local lab) I routinely get in the low 80s apparent attenuation (but that's mashed for high attenuation, which extract is not).

 

[smata67]

1.025 is somewhat high. I got a large batch of Briess LME recently and have brewed four extract beers with four different yeasts and all ended up at 1.019. Typically, about 1 lb of steeping grains in 5 gallons, mostly Caramel 10 or 40. If you used, let's say 2 lb or more of caramel, I can see that high finish. But if you didn't, you should try to bring it down some using the techniques previously described, raising the temperature to mid 70s, swirling a few times a day to rouse yeast (but gently to not introduce oxygen), and adding 4 oz of sterilized corn sugar solution. This should get you results fairly quick, 2 or 3 days at the most. If still stuck, then bottle when fermentation of this additional sugar is complete, it is done. Should be a fine beer, lots of body, but lower ABV than originally planned.

 

[dmtaylor]

Might be shoddy extract. Might also be lack of patience. Give it another week, I bet it will attenuate down to closer to 80% attenuation. If not, try a different brand of extract next time. As others suggested, it's a fact that some extracts simply are not very fermentable by almost any yeast (except maybe diastaticus strains).

 

[redfox]

appreciate all the replies!

yes, hydrometer reading.

and yes, I steeped 2 lbs. of grains (Special B and Caramunich). I even gave it a shot of candi syrup. total OG = 1.072; 5.5 gallon batch.

 

[FatDragon]

Spec. B and Caramunich steeped should add some gravity (since they're already converted so they don't need to be mashed) but they won't be very fermentable, so they'll likely increase the FG. Extract is notorious for finishing a bit high compared to most all-grain brews. How much of a "shot" of candi syrup did you add? That should be pretty close to 100% fermentable and lower the expected FG.

All that together, I'm thinking that 65% seems a bit low and you'll have some more activity. It's possible that it's done, but unlike @smata67, I'm not sure I've ever gotten much less than 80% apparent attenuation with US-05. You might not reach the same level in this brew, but I'd bet you've still got some points to go.

 

[redfox]

sad to say, I did not measure the candi syrup "shot", but I still have the big majority of the package (liquid) I'll use in a Belgian.

 

[redfox]

the continuing saga...

checked gravity this morning, and it reads 1.021, so the yeasties did eat some more since Wednesday evening...