Fermentations finishing high

[jturn3]

I've had problems with my last 3 beers not finishing as low as I expect them to. They've all finish anywhere from .11-.22 higher than the final gravity listed in the recipes I'm using. It's been 3 separate all-grain recipes with two different types of yeast, and I've always bought new yeast and made a 1L starter. I'm fermenting at room temperature, which is keeping the beer at 67-70°.

The weird thing is that I just got my flask and other starter gear recently, so these are the first three batches I've made starters for. I don't know if its all just a coincidence or if there's something wrong in my process. I always boil about 650ml water with 1/2 cup DME, and add some yeast nutrient at the end of the 15 minute boil. Then I pour it into the flask and cool it in a water bath, then pour in the yeast (I've used White Labs vials for all of them so far). Then I insert a foam stopper and let it sit for about 24 hours before pouring into the wort, and I swirl it all around regularly.

Does anyone have any thoughts? The beers have all been fairly standard ales (a porter, an ipa, and a bitter) and I've let them ferment in primary for 7-10 days before checking gravity. I'd greatly appreciate any feedback or suggestions!

 

[Mirkin]

Obviously the yeast is working to get you anywhere, so I'd not be worried about that - except strain, new strains or same as you usually use?

Last year I had a brew that did the same thing, finished high. My problem was my thermometer was uncalibrated and I had mashed 4*C (15-20F) higher than intended, so my fermentables were far lower than intended.

Just a possibility.

 

[daksin]

You haven't been checking your FG with a refractometer have you?

 

[Yooper]

There are two things that come to mind- one is that mash temperatures are critical and maybe the thermometer isn't accurate. The second is if you're checking the FG with a hydrometer vs. a refractometer.

There are other things that come into play- mash pH, aeration, etc, but those first two are likely suspects.

 

[SpeedYellow]

I agree with Yooper- your mash temps are probably high. Is your thermometer calibrated? What mash temps?

For your batches in question, you should calculate your attenuation, and see what the yeast's ranges are. Perhaps you're using a less attenuating yeast than the recipes. But your yeast may be attenuating fine within their range.

It's crazy easy to calculate apparent attenuation; if the OG was 1.060 and ended at 1.020 then the attenuation is 40/60 = 67%.

 

[jturn3]

I'm measuring with a refractometer- is a hydrometer more accurate?

The first two batches that I had issues with were brew-in-a-bag, and my temperatures with those were definitely not consistent. The last one, though, was on my new chest cooler all grain setup and I hit all of my temperatures and gravities (according to my refractometer) pretty well. I had just calibrated my thermometer in boiling water, and was mashing at 151°F for an hour, then fly sparged with 175° water.

My last batch, the bitter, started at 1.046 and has stopped at 1.022, and I used WLP002. If I understand correctly that makes my attenuation 24/46=52% and White Labs' site gives WLP002 63-70% attenuation.

I haven't recalibrated my refactometer since my initial time when I first got it, if that makes a difference.

Thanks so much for the replies!

 

[Cyclman]

You need to use an online calculator to adjust your FG reading when using a refractometer. Here's a link: http://seanterrill.com/2012/01/06/refractometer-calculator/

If you aren't doing this, that would explain the discrepancy. Has to do with the way alcohol bends light vs. sugar water.

Good idea to test your thermo accuracy also.

 

[Yooper]

I'm measuring with a refractometer- is a hydrometer more accurate?

My last batch, the bitter, started at 1.046 and has stopped at 1.022, and I used WLP002. If I understand correctly that makes my attenuation 24/46=52% and White Labs' site gives WLP002 63-70% attenuation.

No, unless you have a way to accurately calculate the FG with software (and I've never found ANY that are accurate for me anyway), the refractometer reading is useless for FG.

To see what we mean, take a hydrometer reading on your "problem" batches. I am sure that they are fine, it was the refractometer reading that was bad.

For my refractometer, my "correction" for that FG would be 1.008.

For great info on refractometers and why this is, check out this site: http://seanterrill.com/2011/04/07/refractometer-fg-results/

 

[jturn3]

Ah, ok. So as I understand it I should use a hydrometer for more consistent and accurate FG readings, but the refractometer is fine for OG measurements and checking the mash/boil gravity? Is that correct?

On a slightly related note, can I use a hydrometer to get a measurement of carbonated beer? Will the carbonation mess with the measurement at all?

Thanks everyone!

 

[Yooper]

Ah, ok. So as I understand it I should use a hydrometer for more consistent and accurate FG readings, but the refractometer is fine for OG measurements and checking the mash/boil gravity? Is that correct?

On a slightly related note, can I use a hydrometer to get a measurement of carbonated beer? Will the carbonation mess with the measurement at all?

Thanks everyone!

To be clear, you can use your refractometer at any time and it will tell you when fermentation is finished. What I mean is this- the brix may be 3 as an example. But if it doesn't change, it's done. THEN you could use your hydrometer to get an accurate reading.

I'd suggest trying sean terrill's conversion formula, and seeing how close it is for you. Maybe you'll have better luck than I did, as I know some brewers claim that it's close enough with the conversion.

As far as a carbonated beer, yes you can take a hydrometer reading. Just stir (or shake) the beer well to remove the carbonation, and then drop the hydrometer into it gently. Spin the hydrometer to knock off any bubbles, and you should get a good reading.

 

[jturn3]

Right, that makes sense. I'll check it out with my hydrometer and go from there. Thanks everyone!