Week-long d-rest... Am I starting too early?

[3toes]

Wrapped up fermentation on a festbier yesterday, with FG being reached at 1.016 (og of 1.057). It took 2 weeks, which isn't uncommon I know for a lager... But I achieved 80% attenuation in one week at 50ºF (1.024), so I was thinking it'd wrap up in 2-3 days with a d-rest at 60ºF. But nope, took an entire week to finish that last 20%.

Is it uncommon to have a week-long d-rest to finish out that last 20%? I keep reading about people saying it takes 2-3 days...

 

[SpeedYellow]

In my experience, 2-3 days can be woefully inadequate and can lead to horrible diacetyl developing over the next few weeks in the keg. I stick with 5 days after going through this a couple times.

BTW, dropping from 1.057 to 1.024 isn't 80% attenuation; it's only 58%. But regardless, you should be fine.

Also, your fermentation took 3 weeks, suggesting that you greatly underpitched. It should be done closer to 10-12 days. Whether or not that hurts your beer quality is another issue.

 

[coyotebrew]

Maybe im doing the math wrong but 41 points of total attenuation to reach final gravity, and he has transitioned through 33 of those points works out to be 80% , but please enlighten me if im doing it wrong. Is there a formula im supposed to be using for this calculation?

 

[jeffcosgrove]

In my experience it depends on the strain. I would normally get to 80% on a beer around 1.055 in 5-6 days and it would finish in 2-3 more. I just made an Octoberfest at 1.054 and it took almost 8 days to reach 80% and another 6 to finish. It was very fresh yeast and I made a more than adequate starter. I think I used Wyeast 2206 Bavarian Lager. Beer turned out great.

I do my calc the way coyotebrew does for when to do the d-rest taking 33/expected total drop. SpeedYellow took 33/57 to get 58%. You would only get to 41/57 = 72% when the beer is finished that way which is the apparent attenuation number you normally see with a yeast description.

 

[SpeedYellow]

Maybe im doing the math wrong but 41 points of total attenuation to reach final gravity, and he has transitioned through 33 of those points works out to be 80% , but please enlighten me if im doing it wrong. Is there a formula im supposed to be using for this calculation?

Ok, here's the problem: the OP used the word "attenuation" as shorthand for "% of the total drop". So yes, 1.024 is 80% of the total drop and yes that's an appropriate time to do a d-rest (but it's not "80% attenuation"). Hope I didn't confuse things by getting hung up on incorrect use of the word "attenuation."

 

[coyotebrew]

Ok i see the confusion, whew glad i had right idea. Another formula...... nooooooooo!!!!!