Chronic underattenuation - help!

[aangel]

So here's the deal: for reasons unknown, I've been unable to ferment beer beyond a 1.025-ish final gravity lately.

-tried stir starters, they're still crapping out early
-tried using fresh liquid yeast, STILL struggling
-oxygenating wort via an aquarium pump through a sanitary filter and a 0.5 micron stone - still struggling

At the moment I've got a dunkelweizen, 1.056 OG, current gravity 1.028, been fermenting a full week at 72 degrees (fermenting, in a keg, with a temp-controlled heat wrap and neoprene sleeve insulator). I pitched 1 million cells per mL (homebrewdad's hybrid pitch rate) of WLP330 belgian ale yeast. My wort was pH 5.5. I oxygenated via the stone for like 3 freaking hours.

It's been a full week and it's not done - despite the fact that it stopped bubbling after day 4. What's going on here? The only thing remaining I can think of is that my grain is old - like 2 years old. Been stored in a sealed container out of the sun the whole time though.

What am I doing wrong here?

 

[giraffe]

Is this all grain or partial mash?
Has this always been the case or a recent problem?

 

[Dcpcooks]

Mash temp?

 

[plazola86]

What's your mash temp?

 

[bigdaddybrew]

Too much crystal malt? Mash temp too high? Thermometer measuring mash temp off? Fermenting too cool?

 

[Cavpilot2000]

Need more details (Extract? AG?, etc).
And 3 hours of pure oxygen is excessive. I've read that anything more than a minute of pure O2 can become detrimental (why, I don't know, but an excessively O2-rich environment is not really healthy for anything, humans included).

 

[TheMadKing]

Are you measuring your FG with a refractometer or hydrometer?

 

[aangel]

I use an aquarium pump (so atmospheric air) through a sanitary filter, so over-oxygenation isn't a problem.

I use a picobrew zymatic on a stepped mash - mash in at 102, then 152 for 30, then 154 for 60. It's their "built in" high efficiency schedule. All gain mash. I control for water salts via bru'n water and pH via use of lactic acid and a pH meter. I'm measuring via a refractometer recently calibrated.

All grain. Fermentation temp 65 ambient but for this last batch I controlled to 72f via a thermal probe on the outside of the fermentation keg, insulated via neoprene.

 

[g-star]

I'm measuring via a refractometer recently calibrated.

That's your problem. Alcohol throws off the readings, and you have to use a calculator to determine FG. Better yet, just use a hydrometer...I'll bet all these beers have attenuated just fine.

 

[TheMadKing]

That's your problem. Alcohol throws off the readings, and you have to use a calculator to determine FG. Better yet, just use a hydrometer...I'll bet all these beers have attenuated just fine.

Yup!

FTFY

 

[Silver_Is_Money]

Despite its potential to be flawed, you could try this online calculator:

http://seanterrill.com/2012/01/06/refractometer-calculator/

 

[LLBeanJ]

I'm measuring via a refractometer recently calibrated.

Are you converting the reading from the refractometer for the presence of alcohol? Once alcohol is present, you can't just take the refractometer reading and call it good. You have to run the reading through a conversion formula.

Do you have a hydrometer? If so, check with that and see what you get.

Edit: Looks like only 3 posters beat me to my answer!

 

[aangel]

Ok, interesting find. I'll have to do my homework to get an offset value to use. Thanks all.

 

[Silver_Is_Money]

The calculator has the offset all set for you. You will need to enter both OG and FG in Brix.