High finishing gravity in porter

Pickngrin · 11-09-2008, 12:58 AM

I brewed a porter a couple of weeks ago with the following grain bill:
8 # British 2-row
1.2 # Maris Otter
1 # Crystal 60L
.75 # Chocolate malt
.25 # Black patent malt

I mashed in my 10 gallon Rubbermaid cooler. I used a new Pyrex digital thermometer, which showed 151 degrees. I have since found that it reads 1-2 degrees higher than actual temp. OG was about 1.054. I used Wyeast 1272 (American Ale II) and fermented in my basement (roughly 65 degrees). Final gravity checked several times before racking to the keg) was 1.022. I don't have an aquarium stone or oxygen bottle or anything and aerate the low-tech way (ie, splashing). Is this likely my reason for the high FG?
I recently had another high FG ale (using the same yeast) but the guy at the LBHS told me perhaps it was due to lack of conversion on that brew.
Any ideas/suggestions?

Thanks

**Jaybird** · 11-09-2008, 02:37 AM

I would think it’s partially from the low mash temp and the low ferment temp. I think I would have brought my ferment temp up to about 70 at the very least and see of it would finish out. You have almost 20% special malts and not all of them are 100% fermentable. You have already keged this so I don’t think there is much you can do to it at this point, but drink it.

JJ

menschmaschine · 11-09-2008, 03:06 AM

Lower mash temps generally yield a more fermentable wort. So, mash temp shouldn't be a problem. What was your water:grain ratio? What was the condition of the yeast pitched? Did you use a starter?

Aeration could have something to do with it, but as long as you splashed it up pretty good, your FG shouldn't be that high solely as a result of that. Your basement temps are a little on the low end but that should still be fine with the heat produced by fermentation. I've fermented ales with an ambient temp of 62F and my attenuation was still OK.

Pickngrin · 11-09-2008, 01:50 PM

That's what I thought re: mash temps. I suppose it is possible that the temperature reading I got was not reflective of the entire mash, but I did try to move the probe around.
I made a starter for the yeast using a bottle of Goya Malta (my first time doing that). This is yeast that I had harvested from the primary fermenter of a pale ale I did,that also finished out with high FG. Water/grain ratio was, I believe, around 1 qt/1 lb.

For my next brew, I will find a way to keep the fermenter closer to 70 degrees and will make sure to aerate well.

Is there something I can do to the corny keg now?

menschmaschine · 11-09-2008, 02:15 PM

Quote:

Originally Posted by Pickngrin

Water/grain ratio was, I believe, around 1 qt/1 lb.

That's a fairly thick mash and can decrease the proportion of maltose in the overall sugar content of the wort. That may have had something to do with it as well, especially if coupled with a higher mash temp than what you thought.