Fermentation problems

[Tuckerl]

So, my last three batches have all had some fermentation issues. None of them have finished anywhere near where they should have. The last two have looked like this: OG 1.074, gravity after two weeks 1.040. The other one had OG of 1.061 and after 6 weeks is at 1.039. Both of these were extract batches with starters brewed and fermented under the same conditions as my last 15 batches which had no issues.
I've tried raising the temp of my fermentation chamber a couple degrees with no results. I've tried gently swirling the wort to get it back in suspension with no luck. And also for the second one, I added Safale 05 in hopes of kick starting with no luck.
At this point I don't know what to do or what the possible causes could be. Any suggestions would be greatly appreciated.
Lee

 

[daksin]

Are you measuring your post-fermentation gravities with a refractometer? Because those don't work once alcohol is in your beer. A 1.040 beer should taste sweet like soda pop- have you tasted either of these beers? I've never seen a fermentation that only went to 30% AA and then stopped.

 

[GilSwillBasementBrews]

If it truly is finished fermenting that high the only reason I could see us an extraordinary amount if unfermentables in your extract. But that's a pretty high gravity reading to finish at. If you are using a hydrometer make sure to make the correct temperature adjustments as well. Or if using a refractometer be sure to do the adjustments for alcohol present in the sample. There are plenty of calculators out there to help attain the correct reading.

If neither are your issues I'm not sure why your FG would be so high.

 

[Tuckerl]

Are you measuring your post-fermentation gravities with a refractometer? Because those don't work once alcohol is in your beer. A 1.040 beer should taste sweet like soda pop- have you tasted either of these beers? I've never seen a fermentation that only went to 30% AA and then stopped.

Yes, I am using a refractometer to measure, I got one recently because my hydrometer broke. I'd never heard that they dont work once alcohol is present in the beer. Maybe I'll run to my LHBS and pick one up to see. I also haven't tasted them so will maybe try at as well.
Thanks! I really hope it is this simple.

 

[squeekybobo]

There are calculators online for using a refractometer after fermentation. Google it, I don't have a link right now :-(

 

[daksin]

Yes, I am using a refractometer to measure, I got one recently because my hydrometer broke. I'd never heard that they dont work once alcohol is present in the beer. Maybe I'll run to my LHBS and pick one up to see. I also haven't tasted them so will maybe try at as well.
Thanks! I really hope it is this simple.

Yup, there's your problem. A refractometer is going to read way high with alcohol in solution because it measures the concentration of sugar by seeing how much the index of refraction of water (how much light is bent passing through water) is altered by sugar in solution. Alcohol has a very different index of refraction than water so the refractometer scale doesn't work any more.

I would also avoid using a calculator to really judge what your FG is because there a few and none of them are really any good (it really is guesswork). BUT if you do plug your numbers into one, you'll see you're much lower than your refractometer is reporting.

 

[squeekybobo]

I would also avoid using a calculator to really judge what your FG is because there a few and none of them are really any good (it really is guesswork). BUT if you do plug your numbers into one, you'll see you're much lower than your refractometer is reporting.

I use Brewbot on the iPhone. I compared the calculator to a hydrometer reading, and it's very close. My last batch of Belgian blonde calculated to 1.009 on the calculator, hydro said 1.010.

 

[Tuckerl]

Thank you to everyone, that was exactly my problem. I used a hydrometer today and they both were in the range of where they should have been. Thanks again for the help!

 

[Brulosopher]

This is the best refractometer calculator by far: http://seanterrill.com/2012/01/06/refractometer-calculator/

Very accurate. I still use a hydro for FG... just because I wanna taste.

 

[squeekybobo]

This is the best refractometer calculator by far: http://seanterrill.com/2012/01/06/refractometer-calculator/

Very accurate. I still use a hydro for FG... just because I wanna taste.

That's why I still use the thief for the couple drops for the refractometer ;-)

 

[Brulosopher]

That's why I still use the thief for the couple drops for the refractometer ;-)

Haha