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Brews & Views Bulletin Board Service * Brews and Views Archive 2004 * Archive through September 09, 2004 * Overattenuation? < Previous Next >

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George Schmidt
Junior Member
Username: Gschmidt

Post Number: 72
Registered: 08-2004
Posted on Thursday, September 09, 2004 - 05:56 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

So, I decided not to bottle the wit tonight because it got too late on me, and I need some more bottles anyway. But I did take a sample and a taste. Good tasting, no off flavors, but a bit thin bodied. Running the numbers through promash has me confused, maybe you folks can shed some light.

The original OG, measured with the hydrometer was 1.046. Tonight's FG was 1.004 w/hydro and 5.0Bx w/refract. The numbers are consistent per promash, with the backtrack OG from tonight's readings right at 46. Problem is, that is a 91% apparent attenuation. Wy3944 is only supposed to do 73-77% What the heck happened? This thing had 1/2# of oats, along with 4.5# wheat, 3/4# flaked wheat, and 7# barley. I did not do a protein rest. There should have been plenty of unfermentables. It did a long, steady primary of 3 weeks at 65F-ish and about two weeks so far in secondary with no bubbles.

The only thing I can think of is that I was still using the analog thermometer for this mash. I did a single infusion at supposedly 154F. If the thermometer is low, and I actually mashed at say 145F, the wort would be more fermentable, right, but would it be 15% more fermentable? Any other ideas?

I'm still going to bottle it tomorrow. As I said, it still tastes good. I just want to keep this from happening again. Your advice is, as always, greatly appreciated.

Senior Member
Username: Fredrik

Post Number: 1594
Registered: 03-2003
Posted on Thursday, September 09, 2004 - 08:40 am:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I don't know if that is your issue, but according to my extremely crude ballpark estimates(best I have atm) for mashing it is certainly possible.

I don't konw what FG you expected, but supposed you'd expect an FG @ 1.011-1.013 when mashing @ 154F for that strain and OG, then according to some crude estimates my best wild guess assuming you'd end up mashing @ 144F, would think you could expect FG 1.004-1.006. This would be quite consistent with your mashing and the strains rated maltotriose depletion.

So give or take some point, I would say that if your temp is off that much, it can consistently explanation your FG.


Brandon Dachel
Senior Member
Username: Brandon

Post Number: 1200
Registered: 03-2002
Posted on Thursday, September 09, 2004 - 12:23 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

I've had that strain of yeast make some pretty dry (read thin) wits before. 1.004 seems really, really low without the addition of kettle sugars, but if you're measuring it with temp-corrected, calibrated instruments then that's what it is.

Denny Conn
Senior Member
Username: Denny

Post Number: 3470
Registered: 01-2001
Posted on Thursday, September 09, 2004 - 08:46 pm:   Edit Post Delete Post View Post/Check IP    Ban Poster IP (Moderator/Admin only)

"If the thermometer is low"...actually, if the thermometer reads high, you'll be mnashing at a lower temp. I know, it's happened to me! I broke down and bought a lab calibration thermometer and recalibrate all my thermometers every few sessions. Be sure to calibrate them in the mash temp range, not at freezing/boiling.
LIfe begins at 60...1.060, that is.