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Old 02-06-2010, 10:03 PM   #1
imperial
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Default Did I Overpitch?

I know, your first thought is, "One cannot overpitch!" But hear me out.

I used Wyeast 1728 Scottish Ale (http://www.wyeastlab.com/hb_yeaststr...ail.cfm?ID=143). It has a 69-73% attenuation (is the real or apparent?). It is rated to go up to 12% ABV.

I pitched ~250ml thick yeast slurry into 5gal of 1.105 wort. I've been monitoring the ferment, and here are the numbers that I've read:

hours - SG
24 - 1.039
48 - 1.033
>48 - 1.032

It's now been 4 days since I pitched.

So it pretty much stopped fermenting after 48 hour. But the fermenting it did in the first 48 hours was pretty amazing.

I should also mention that I keep my ferments locked in at 69F in a fermentation box with a thermostat.

I calculate my apparent attenuation at ~70% and my real attenuation at ~57%.

If the attenuation that Wyeast lists (69-73%) is real, then there is definitely something wrong. And, even if it's the apparent attenuation that's listed, I still feel like it should have been on the high end of the attenuation range (73%). Maybe I'm splitting hairs?

Or maybe I just need to wait a while longer. But it doesn't seem to be moving anymore.

I've been rigorously shaking the fermenting bucket daily to try and encourage fermentation. 1728 is a highly flocculant (is that a word?) yeast.

Thoughts? Thanks!

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Old 02-06-2010, 11:21 PM   #2
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Dude, it's only day 4? Let it go for another couple of weeks. Yeast really slow down passing the 9% mark. If you like, add a few teaspoons of yeast nutrient.

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Old 02-06-2010, 11:30 PM   #3
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Should you be shaking the fermentation vessel? Yeast activity increases rapidly in the beginning and than begins to decelerate as it approaches its limit. Meaning basically 80% of the sugar is consumed in 20% of the time and the other 20% of the sugar is consumed over the last 80% of the time...(Pareto)

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Old 02-06-2010, 11:47 PM   #4
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I'd also add that I'm pretty sure the expected fermentation range is based on apparent, not real.

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Old 02-07-2010, 12:11 AM   #5
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Quote:
Originally Posted by McGarnigle View Post
I'd also add that I'm pretty sure the expected fermentation range is based on apparent, not real.
This is correct. Wyeast always lists apparent attenuation.
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Old 02-07-2010, 02:36 AM   #6
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Quote:
Originally Posted by rocketman768 View Post
Dude, it's only day 4? Let it go for another couple of weeks. Yeast really slow down passing the 9% mark. If you like, add a few teaspoons of yeast nutrient.
I guess I may be a little impatient
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Old 02-07-2010, 02:57 AM   #7
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Numbers listed for attenuation on wyeast/white labs sites or any homebrew forums are usually for apparent attenuation. Most of your primary fermentation will probably be done within 4-5 days anyway. Unless you're just trying to see how your particular fermentations are running, I would not even bother taking hydro readings until about a week is up. Also, did you make a starter? How did you get 250ml of thick slurry? Did you repitch from yeast you got from a local brewery perhaps? Anyway, that seems like the norm for typical fermentations. Congrats that it seems like it will finish quickly, that means things are going as expected.

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Old 02-07-2010, 08:40 PM   #8
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Thanks for the input, ilinibrew04!

I do a 2L starter, decant off the beer, then a 6L starter to get to 250ml thick yeast slurry.

I think you're absolutely right about the 4-5 days for a primary ferment to finish. I spoke with a pro brewer who does a lot of high grav beers, and he said they try and have their ferments done in three days.

Any idea how much more I can expect the gravity to drop after the initial ferment?

I like to do readings every 12 or 24 hours early on in my ferments so I can track what's going on for future reference. Then I'll know when to be worried or when it's just normal. Also, I'm using a refractometer, so it's pretty easy to sanitize a dropper and get a few ml of beer.

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Old 02-07-2010, 08:46 PM   #9
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give us some more info about the wort. was this an extract or AG recipe, a recipe would be nice. either way you are in the target range of the yeast attenuation.

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Old 02-08-2010, 05:10 AM   #10
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Quote:
Originally Posted by TipsyDragon View Post
give us some more info about the wort. was this an extract or AG recipe, a recipe would be nice. either way you are in the target range of the yeast attenuation.
It was AG. Here's the grain bill:

14# Maris Otter
3# Biscuit
3# Crystal 60
8oz Wheat
4oz Smoked

It was a 5.5gal batch.
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