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Home Brew Forums > Home Brewing Beer > Fermentation & Yeast > Partial Mash Fermentation / FG Problems?
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Old 11-08-2010, 04:18 PM   #1
sflabrew
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Default Partial Mash Fermentation / FG Problems?

I have a question for everyone that is as old as time but I'm hoping that if I give details someone can point out what I've done wrong...

I've been brewing extract with specialty grain for just under a year. In the beginning I had issues getting the FG I wanted but found my problem was in cooling the wort (I hadn't been getting it down below 80, 90 was good enough for me at the time... stupid.) I finally got the fermentations I wanted with an IPA and a blonde and was all excited...

But a couple weeks back I decided to make an oatmeal stout for this winter. I did my research and found that this was the time to start partial mashing. I followed the partial mashing directions in "Brewing Classic Styles" by Zainasheff and Palmer. The only thing I did differently was that I left my grain bag in the second pot for 20 minutes instead of 10 (I read, probably on here, that I would get greater efficiency if I did this.

THE PROBLEM: After 2 weeks in the fermenters I had a FG of 1.038.

Here is my recipe...


Extracts:
8 lbs Pale Malt Extract

Grains:
3 lb Flaked Oats
2 lbs American 2 Row
1 lb Chocolate Malt
1 lb Victory Malt
½ lb Crystal 80L
½ lb Roasted Barley

Grain Notes: Request the oats to be in a separate bag so that you can toast them before adding them to the rest of the grains for mash.

Hops:
1 oz Williamette 60 minutes
1 oz Williamette 15 minutes

Special:
1 teaspoons ground cinnamon 15 minutes
1 ½ teaspoon ground cinnamon 5 minutes

Mashing: This is going to be a Partial Mash brew.

Yeast:
White Labs Irish Ale Yeast WLP004

Extra Flavoring:
1. Toast oats in the oven at 300F until they begin to slightly color and give off a nutty cookie aroma.

OG 1.075
FG 1.038

The temp in my fermenting closet was probably right at 68 but here in socal the temp does go up and down quite a bit. I do my best to maintain a steady temp.

Did I use too much oat and not enough 2row? Too much oat in general? Was it that I decided to try the wlp004? Do I need to maybe aerate my wort more? The wort temp was definitely 80 or just below before I put it into the fermenter.

Your opinions would be greatly appreciated. There is nothing more annoying than getting that FG. Thanks for reading all of that.

-sflabrew

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Old 11-08-2010, 04:58 PM   #2
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Sorry if I missed it, but what temp did you mash your grains at?

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Old 11-08-2010, 06:01 PM   #3
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Brought temp up to 165 then killed heat and put in grain bag. Maintained 155 for an hour before taking grain bag to second pot. 2nd pot was also raised to 165 and then cut with intro of grains and mantained 155 for 20 minutes.
Thanks!

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Old 11-08-2010, 06:18 PM   #4
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I have few concerns about the amount of Oats used, which seems too much for a 5gal batch.
The 2row may not have enough diastatic power to covert itself plus all the starch from the oats, so you may have ended with too much starch unconverted and a thick wort that will be carried to you final gravity. A thick wort sometimes may also affect how your hydrometer/Refractometer works.
When I plug your recipe to my brewing tool, I get an FG of 1.022.
You have right now about 4.7% ABV, which is already within style.
I don't think you have a stuck fermentation, just stuff that the yeast can't deal with.

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Old 11-08-2010, 06:55 PM   #5
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Thanks Nilo!

I had my worries about that. Do you mind if I ask what your brewing tool is? Is this a website or freeware program?

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Old 11-08-2010, 07:01 PM   #6
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I built my own brewing tool in excel. Not very far from all other tools but with some better job when using unfermentable sugars, like lactose, dextrin or crystal malts. It also takes into account the mashing temperature when calculating the the yeast attenuation.

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Old 01-05-2011, 11:29 PM   #7
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Quote:
Originally Posted by nilo View Post
I have few concerns about the amount of Oats used, which seems too much for a 5gal batch.
The 2row may not have enough diastatic power to covert itself plus all the starch from the oats, so you may have ended with too much starch unconverted and a thick wort that will be carried to you final gravity. A thick wort sometimes may also affect how your hydrometer/Refractometer works.
When I plug your recipe to my brewing tool, I get an FG of 1.022.
You have right now about 4.7% ABV, which is already within style.
I don't think you have a stuck fermentation, just stuff that the yeast can't deal with.
I just made a similar mistake with my second batch. I definately did not get good conversion on my batch that is fermenting. Question is, what do you do now? Is it going to be drinkable in some way? Fixable? Best to just pitch it and start over?

Great thread!
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Old 01-06-2011, 03:57 AM   #8
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Quote:
Originally Posted by wdleonard View Post
I just made a similar mistake with my second batch. I definately did not get good conversion on my batch that is fermenting. Question is, what do you do now? Is it going to be drinkable in some way? Fixable? Best to just pitch it and start over?

Great thread!
I bottled it!

It's more malty than I'd like but my friends have enjoyed it and there have been a couple cold nights (as cold as Southern Cali gets) that it has really warmed me up.

If you don't bottle then I'd suggest you brew up another, or something that would go well with it, and blend the two! No reason to toss the batch and your cash.

I have used oats in batches since this and adjusted my 2 row to oat ratio and they have been successful.

Good luck to you sir!
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