[Pawtucket Patriot]

Several of my recent brews have been way overattenuated (~85% apparent attenuation) and I'm trying to identify the issue.  

Here is some info on the overattenuated batches
First, these batches have involved grain bills with little, if any, caramel malt.  I'm starting to wonder if I need to start adding some dextrin malt to my pils/helles-type beers just to add a slight amount of unfermentable material.

Second, I've been using acid malt for most of the lighter batches that have overattenuated.  I have been consistently hitting a mash pH of 5.3-5.5 for the batches in question.

Third, most of these batches have started with 12P worts.

Fourth, these batches were mostly fermented with WLP833 and Wyeast 2206.  For a five gallon lager batch, I make a 2L stirplate starter with 2 smackpacks/vials.

Finally, I mashed almost all these beers around 150 for 60 min.

I just tested my brewing thermometers yesterday and my dial thermometer, which I use to measure the temp of my water infusions, was way off (at least 10 degrees at freezing and boiling).  But my traceable digital thermometer, which I use to measure mash temp, was dead on.  So, I feel like I can rule out a thermometer issue.

[bluesman]

Some dextrin malt would give you more dextrins (mouthfeel). I think the acid malt may also contribute to a percertion of thinner body. The main consideration is your mash temp, try bumping up a degree or two which will reduce your AA%. I would question your temps but you said you've calibrated your thermometer and it is dead on.

I would try increasing your mash temp before changing anything else. If that doesn't give you desired results then I would add some dextrin malt.

[mabrungard]

150F is a fairly modest mashing temp.  If you were looking for less fermentability, that is the first thing that needs to be increased.  I also see that you're fermenting lagers and those yeasts can be more attenuative than an ale yeast. 

I understand that some digital thermometers are pretty accurate and I see that you mention its got a 'traceable' rating.  I'm not sure how the manufacturers do the testing, but I would still recommend checking the thermometer with a NIST traceable mercury thermometer at a more typical mashing temperature (say 140 to 160F).   There can be all kinds of error in measurement even if the thermometer reads correctly at freezing and boiling. 

With regard to mash pH, I would avoid allowing your mash to fall below 5.4 (room-temp measurement) since I find that fermentability increases as the mash pH decreases.  I've made some thin beers when I overacidified my mash.

[Hokerer]

In addition to the temp issues, how are you measuring your mash pH?  Might have "calibration" issues there too.

[Pawtucket Patriot]

In addition to the temp issues, how are you measuring your mash pH?  Might have "calibration" issues there too.

Yeah, I readily admit that I'm measuring mash pH with ColorpHast strips, which are probably not the most accurate way to measure.  But, when I do the +.3 correction, my mash pH is almost always within .1 of what Bru'n Water predicts.

[a10t2]

I've brewed with 2206 pretty extensively and that sounds typical to me. With an all-base malt grist and moderate (66-68°C) mash temps, ADFs have been 76-83%.

[Pawtucket Patriot]

I've brewed with 2206 pretty extensively and that sounds typical to me. With an all-base malt grist and moderate (66-68°C) mash temps, ADFs have been 76-83%.

Ok, that's good info.  And lest anyone think I'm a complete r-tard, I only felt like my attenuation rates were anomalous/problematic because I've seen other brewers who use similar grists/mash temps/yeast get different results, i.e., less attenuation.  But I suppose there could be a lot of other factors at work there.

I'll try mashing higher for these beers in the future, probably closer to 154 for a single infusion. 

[euge]

Can you tell us of any departures from your traditional brewing method? Anything new?

[wildknight]

Are you strictly using a refractometer?  If you are, then remember that those are only accurate using malt.  The ethanol in the beer throws off the readings.  There are many different calculators out there to convert Brix to specific gravity after fermentation, but none are precisely accurate.  I had one tell me my English mild was 1.004 based on the conversion from Brix, but when I put it in an actual hydrometer it read 1.012. 

[Kit B]

Are you doing any mashout?
Do you start boiling your first runnings, as soon as they are in the kettle?

I have noticed that my beers tend to have very high attenuation & can only track it down to these two parts of my process (lacking).
I rarely do a mashout, to stop enzyme activity.
And, I normally wait until all my runnings are in the same kettle, to start the boil.
I hypothesize that this allows longer enzyme activity, at falling temperatures (in my brews).

[tschmidlin]

Are you strictly using a refractometer?  If you are, then remember that those are only accurate using malt.  The ethanol in the beer throws off the readings.  There are many different calculators out there to convert Brix to specific gravity after fermentation, but none are precisely accurate.  I had one tell me my English mild was 1.004 based on the conversion from Brix, but when I put it in an actual hydrometer it read 1.012. 

This is really odd - typically it would be the other way around, with the refractometer reading higher due to the alcohol than the hydrometer would.

[a10t2]

I had one tell me my English mild was 1.004 based on the conversion from Brix, but when I put it in an actual hydrometer it read 1.012.

This is really odd - typically it would be the other way around, with the refractometer reading higher due to the alcohol than the hydrometer would.

I think he meant after applying a correction. In that case, the "standard" correlation almost always gives a result below the actual FG.

http://seanterrill.com/2010/06/11/refractometer-estimates-of-final-gravity/

[tschmidlin]

I had one tell me my English mild was 1.004 based on the conversion from Brix, but when I put it in an actual hydrometer it read 1.012.

This is really odd - typically it would be the other way around, with the refractometer reading higher due to the alcohol than the hydrometer would.

I think he meant after applying a correction. In that case, the "standard" correlation almost always gives a result below the actual FG.

http://seanterrill.com/2010/06/11/refractometer-estimates-of-final-gravity/

Ah, that makes much more sense.  A failure of reading comprehension

[Pawtucket Patriot]

Can you tell us of any departures from your traditional brewing method? Anything new?

I have changed a few things over the past year. First, I changed the way I approach water adjustments. Instead of using chalk to raise mash pH, I now only use pickling lime. Also, I add fewer flavor ions in the kettle than I had before. I usually try to track the suggested style profiles on Bru'n Water (e.g., yellow balanced, brown malty, etc.) rather than trying to emulate "published" city profiles.

Second, I use acid malt exclusively for lowering mash pH. I add 1% acid malt to lower mash pH by .1. Again, measuring with colorpHast strips, I am almost always within .1 of my pH target, which is 5.4.

[Pawtucket Patriot]

Are you doing any mashout?
Do you start boiling your first runnings, as soon as they are in the kettle?

I have noticed that my beers tend to have very high attenuation & can only track it down to these two parts of my process (lacking).
I rarely do a mashout, to stop enzyme activity.
And, I normally wait until all my runnings are in the same kettle, to start the boil.
I hypothesize that this allows longer enzyme activity, at falling temperatures (in my brews).

I do a boiling water infusion at the end of the mash that occasionally raises the grained temps to actual mahout temps. But most of the time, this infusion only raises the mash temp to the low 160s. I do, however, raise the grainbed temp to 170 with my batch spare infusion. I would think this would do a lot to halt enzymatic activity.