Fermentation stopped well short after 14 days

[bryangm]

I recently brewed a Christmas spiced beer. I started with an OG of 1.070 and used a yeast starter of Wyeast 1275. I refrigerated the yeast starter for 24 hours and decanted most of the spent wort. I let it warm up for a couple hours before pitching.

I stored the carboy in my 66 degree basement, in a 32 gallon garbage can with the lid on to protect it from sunlight. Fermentation was going great for the first 2 days, at 72-74 degrees (the upper range for 1275). I removed the blowoff since it was no longer needed and put on an airlock. Afterwards, fermentation seemed to slow, and the airlock barely bubbled. I tested its seal and it seemed no different than any other time I've used it.

With 1275's 74-76% attenuation, I was expecting a FG of around 1.020. However, It was nowhere close, coming in a 1.039.

Any ideas what I did wrong, and what I should do to correct it?

 

[WoodlandBrew]

Could it be measurement error? If you are using a refractometer for final gravity it could be off by quite a bit due to alcohol in the beer. Also it's pretty easy to knock a hyrometer out. See this link:

http://woodlandbrew.blogspot.com/2012/10/brew-house-efficiency.html

If your FG really is that high, then it is likely fermentables. What were your mash temps? Does your thermometer measure 212 in boiling water? How about recipe: Carapils? Crystal Malt?

 

[bryangm]

Thanks WoodlandBrew. It was an extract kit from Midwest Supplies...so it was mostly extract with a small amount of specialty grains. I used a refractometer to check the gravity both times, making sure it was at 1.000 using tap water to make sure I didn't need to calibrate it.

I beginning to think that despite the temp range on the yeast being 62-72 degrees, 66-68 was a bit cold for the yeast.

 

[WoodlandBrew]

Did you use a calculator to compensate for the alcohol in the beer when using the refractometer? Like this one:
http://onebeer.net/refractometer.shtml

I plugged in your numbers and the corrected FG is 1.019 for a 6.8% ABV. So good news! Looks like your beer is right on target!

(FWIW, 66-68 is not cool for almost any brewing yeast. It's actualy warm for most yeasts)

 

[bryangm]

Well look at that! I have no idea refractometers were effected by alcohol. If I used a hydrometer, could I expect to see 1.019? (I'm at work and can't try it until tonight)

 

[tre9er]

Well look at that! I have no idea refractometers were effected by alcohol. If I used a hydrometer, could I expect to see 1.019? (I'm at work and can't try it until tonight)

Yes. Hydrometers only require correction for the temperature of the beer not equal to 60*, which is the temp for which it's calibrated.

 

[bryangm]

Much appreciated...thanks everyone!