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andycr · 12-19-2012, 09:14 PM

If there's one thing I have a problem with, it's attenuation. It, more than any other process in my brewing hobby, seems to be more random than scientific.

No, WLP004, you shouldn't finish Ode to Arthur at 1.020. Bad yeasts. I mashed at 152, what more do you want.

Next time I'll mash at around 148 for a dry Irish stout, I think. Roused it and waiting a few days, but I doubt it's anything but done. Stupid yeast.

**bink00** · 12-19-2012, 09:29 PM

Have you verified your temp prob, thermometer, rtd, or whatever you use? I had a cheapo TC that wasnt right and I didnt figure it until 2 batches did what you are describing...but im a noob so take what I say with a grain of salt

**Hammy71** · 12-19-2012, 10:37 PM

Checking your thermometer is an excellent place to start. Often beers with a lot of 'darker' malts can be a little tricky to get down to the FG we want. Mashing lower should help, but you run the risk of making a 'watery' stout with little or no mouth feel. For me, when I mastered my aeration practices; the 'stuck' fermentations went away. I haven't had anything finish too high (knock on wood) for years now. Something simple as a wine degassing whip and a thermometer that can be calibrated has made my brews and my yeast happy. Not saying this will fix all your problems, just what has helped me.

andycr · 12-20-2012, 01:00 AM

I'm wondering about my thermometer, I'll check it against my analog one next time. I aerate pretty thoroughly and have yet to get a truly stuck fermentation, just ones that end higher than expected... Pitching rate is always good by my check (1L starters for 2.5 gallons).

Since Ode to Arthur uses 25% flaked barley, I'm betting I can get away with a lower mash temp without sacrificing body. Good to try next time I brew it.

**aiptasia** · 12-20-2012, 01:07 AM

That's usually my issue with attenuation, mash temps that creep up a little too high if i'm not paying attention to them.

Dok · 12-20-2012, 04:39 AM

I never paid much attention to how well my thermometer worked. I have a collection of about 6 different ones. My Uncle's girlfriend works in restaurants and she showed me the best thermometers are he ones that you can calibrate by adjusting the nut on the back side. She gave me one of hers and I calibrated it using ice cubes and boiling water. I tested it against all the other I used for the last few years. Oh my god where they way off. No wonder I had attenuation problems. I mean off by +/- 5 degrees.

william_shakes_beer · 12-20-2012, 12:57 PM

I found thermal industries makes fairly accurate digital thermometers. I also found most taylor tyhermometers off by 11 degrees or so. Thermal Industries makes Thermopen and others. Question: Are thermometers that are based on physics more reliable than those that rely on an electronic sensor? For instance, a mercury (silver) or alcohol (usually died red) thermometer is based on volume increases of thoase materials due to thermal expansion. Seems to my limited understanding that those would be good reference sources. I'm not advocating accepting the risk of contaminating a batch with a broken mercury thermometer, but I'd consider getting one for calibration purposes. The challenge as I see it is in getting an accurate reference point. We all can make an ice bath with salt to approach 32F, and adjust a rolling boil for alditude, but those are not the temps we mash at.

WoodlandBrew · 12-20-2012, 01:06 PM

My number one thought was also temperature.
How to calibrate a digital thermometer:
http://woodlandbrew.blogspot.com/2012/10/mash-temperature-and-thermometers.html

My second thought is sterol depletion. Are you pitching from a slurry, and are you using a stir plate?

And here are some more ideas:
http://woodlandbrew.blogspot.com/2012/11/top-ten-reasons-why-your-final-gravity.html

andycr · 01-04-2013, 03:24 PM

Hmm, pretty sure it's my thermometer. Now that I think about it, it's meant to be a meat thermometer, so I bet it under-reports the temperature to appease the gods of food safety.

I'll have to check it more carefully against my analog one on tomorrow's brewday.

WoodlandBrew · 01-04-2013, 03:37 PM

If you check them both against boiling water it might give you a good idea of the deviation at mash temperatures.