Underattenuation

[thatguy314]

Lately I've been having some trouble getting my beers to attenuate. None of them taste particularly sweet (I've had other judges taste them and no one has commented that they seem underattenuated, or have any particular off-flavors), but the finishing gravities have been quite high (~1.020). This is strange, because traditionally my beers have, if anything, over-attenuated.

- I haven't changed anything in my brewing process.
- I've checked my mash thermometers against a mercury lab thermometer at 64C/147F and it's within one degree so I know my mash temperatures are not significantly off.
- I use oxygen (1 minute, just enough pressure to make the bubbles break the surface of the wort in the carboy, don't have a flow meter)
- I pitch according to the mr. malty (or occasionally do a count myself).
- My brewing statistics have always been very reproducible when I repeat recipes (OG and FG within 2 points)
- % attenuation has been well under 70% with yeasts that tend to attenuate ~70-75% (WLP007 dry english went 1.058-10.20 and WLP380 Heffeweizen iV went 1.070-1.024. Any thoughts?
- I stress again, that in 4 years I've never had underattenuation problems. the WLP007 recipe attenuated down to 1.014 last time I made it, exact same recipe

[dmtaylor]

I don't think we have quite enough information. What are your mash temperatures? How long do you mash? What are your fermentation temperatures? Have you calibrated your fermentation thermometer? Are you letting the beer sit at fermentation temperature long enough, or are you crashing cold at some point? You might be racking to secondary too early. If you rack to secondary, consider leaving your beer in an extended primary instead. I don't do secondaries anymore, one reason being that it can cause fermentation to stop too early.

Consider all these ideas, and everything else under the sun. There has GOT to be something different from what you have had in the past, and you're just not thinking of it, or if it is equipment related, you just have not found it yet.

[TastyMcD]

If the beers aren't tasting under attenuated then I'm thinking you're getting more unfermentable sugars into your ferementor than usual. Since you calibrated your thermometers, I'm wondering if your mash Ph isn't high or there's some mineral that the yeast need that they aren't getting? Have you changed your water chemistry lately?

Tasty

[thatguy314]

There has GOT to be something different from what you have had in the past, and you're just not thinking of it, or if it is equipment related, you just have not found it yet.

That's exactly what I was thinking of. The mash temps have varied. The amber (WLP007) I mashed at 154 to get a little bit of unfermentable sugar and add body, but as I said, last time that gave me a 1.014 finishing gravity, instead of the 1.010 I would expect from a 150ish rest.

If the beers aren't tasting under attenuated then I'm thinking you're getting more unfermentable sugars into your ferementor than usual. Since you calibrated your thermometers, I'm wondering if your mash Ph isn't high or there's some mineral that the yeast need that they aren't getting? Have you changed your water chemistry lately?

Tasty

pH is something I should look at a little more. I was very vigorous about checking it my first 2 years of all-grain, but I've rarely had a problem hitting a good pH by sticking to palmer's sheet (as long as I'm not doing a really dark beer). In the past month (when I brewed these last few beers) I've been out of pH strips and I've since ordered some of the colorphast strips from morebeer.

I know my apartment is right on the border between the 2 water systems that feed NYC, both are fairly neutral but there is a reasonable difference in residual alkalinity. It's certainly possible that my building might have changed from a croton source to a catskill source, changing things around a bit. i ran out of pH strips recently (have some more on order), but I try to stick to the Palmer sheet for every brew. My water is fairly neutral with high chloride, so I bring it to balanced sulfate/chloride, to highly sulfated (depending on the brew). I always shoot for about 100ppm of calcium in the mash and balance the calcium and bicarm to meet the appropriate SRM based on palmer's sheet. The mash is typically iodine negative within 30 minutes, but I usually hold a 60 minute mash to be safe (and because I often have other things to do to get ready for the brew day, like weigh out hops, clean carboys, etc.,). The neighboring water system, which

The below water profiles are based on the city's water report, not based on any testing I've done. I suppose I could test the water myself, but I'm not sure I have all the supplies in my lab having never done this.
My water (croton water): Ca 22, Mg 7, Alkalinity (as CaCo3) 56, Na 28, Cl 56, S04 11,
Neighboring water (catskill water): Ca 5, Mg 1, Alkalinity (as CaCo3) 13, Na 8, Cl 9, S04 5,

[Weenie Boy]

You may want to also check the calibration of the instrument(s) that you take your gravity readings with.

Weenie Boy

[thatguy314]

You may want to also check the calibration of the instrument(s) that you take your gravity readings with.

Weenie Boy

True. I'm going to take some distilled water home and check both my hydrometers tonight. That sucks if my hydrometer was off, that would make both my OG off too, and I've been (at least I thought) hitting that perfectly for a while now.

[brewinhard]

+1 to checking your hydrometers as well. The problem is that even using distilled water cannot be accurate enough. Any way you could check your hydrometer with say a local brewpub's equipment to help calibrate it better? And when you say you calibrated your mash thermometer with a lab grade mercury thermometer there could still be errors. Even lab grade thermometers can be off by several degrees which would lead yours to be off as well. Have you compared yours to any friends who are homebrewing well and nailing their numbers? I know this sounds strange, but I have always calibrated my thermometers by brewing a couple of JZ's recipes in BCS. I guess I always figured that if I nail the OG and FG in several of his recipes repeatedly, then I know I have adjusted my thermometer to be calibrated for those recipes and therefore assume that my thermometer is fairly accurate. Or, if this does not sound good to you, then you could always brew the same recipe a couple times in a row the exact same way and slowly dial in on the target temp of the mash to hit your desired FG. Then you will know how far off your thermometer is for other brews, or at least have a starting point to go from. I feel your pain, as this happened to me 3 years ago, except all my beers were over attenuating, like down to 1.002 or so. They still tasted great, and led me to really enjoy the flavors of malt.

[thatguy314]

+1 to checking your hydrometers as well. The problem is that even using distilled water cannot be accurate enough. Any way you could check your hydrometer with say a local brewpub's equipment to help calibrate it better? And when you say you calibrated your mash thermometer with a lab grade mercury thermometer there could still be errors. Even lab grade thermometers can be off by several degrees which would lead yours to be off as well. Have you compared yours to any friends who are homebrewing well and nailing their numbers? I know this sounds strange, but I have always calibrated my thermometers by brewing a couple of JZ's recipes in BCS. I guess I always figured that if I nail the OG and FG in several of his recipes repeatedly, then I know I have adjusted my thermometer to be calibrated for those recipes and therefore assume that my thermometer is fairly accurate. Or, if this does not sound good to you, then you could always brew the same recipe a couple times in a row the exact same way and slowly dial in on the target temp of the mash to hit your desired FG. Then you will know how far off your thermometer is for other brews, or at least have a starting point to go from. I feel your pain, as this happened to me 3 years ago, except all my beers were over attenuating, like down to 1.002 or so. They still tasted great, and led me to really enjoy the flavors of malt.

Re: calibrating the hydrometer--As far as I understand it, hydrometers lose their calibration when the paper on the inside moves and the numbers are wrong. I'm not sure what brewery equipment I can use to calibrate my hydrometer. A refractometer? I can also use DME to make a fixed volume solution so that I know a precise gravity and can check it at 0 and another level. Is there another way to calibrate it other than to just check it against other equipment?

Mercury doesn't just suddenly change its physical properties. Mercury thermometers lose their calibration in 2 ways: 1) the paper on the inside slides as with hydrometers or 2) something leaks in or out of the mercury. However the thermometers I use in lab don't have a paper backing, but have their numbers etched into the glass behind it precisely so they don't slide, so I can be reasonable sure they're accurate. That said, I actually have 2 identical thermometers and in my lab I have several mercury and alcohol thermometers. They all read the same, so I'm confident they're correct.

Prior to this I have brewed several BCS recipes and have gotten pretty much entirely the exact same numbers. I suppose I could go back and try that, but I think it's just going to show me what I've seen with my other recipes.