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I know there are several questions on the forum about OG being lower than predicted. Please bear with me though. I'm at a loss. I just brewed a straightforward extract wheat beer recipe. The fermentables were:

  • 0.5 lb Crystal 60L, steeped in 0.5 gallons 150F water for 20 minutes, sparged (rinsed) with 0.5 gallons 150F water
  • 5.5 lb Briess light DME
  • 0.5 lb Briess wheat DME

My recipe listed the OG as 1.051-1.053. Beer Calculus puts it at 1.055. My OG reading came in at 1.090. That's really, really high. What gives. Here's what I can rule out:

  • Inaccurate hydrometer. I tested it in 60F water and it reads 1.000.
  • Added too much DME. I quadrouple checked. I used a 5 lb sack of light DME from Austin Homebrew. I measured another 0.5 lb, and measured out 0.5 lb of wheat DME. I did not weigh the 5 lb sack to ensure it was 5 lbs. The label does say 5 lb.
  • Final volume - I used 5.5 gallons of spring water today - 2.5 in the boil, 3 to top off the fermenter.

Possible causes:

  • Hop debris. I did not filter the wort when pouring it into the fermenter. The sample I took for the OG had a lot of pellet hop debris in it. Could this provide lift to the hydrometer?
  • Poorly mixed wort. I poured the 2.5 gallons of cooled wort into the fermenter then added 3 gallons of bottled spring water. Maybe it wasn't thoroughly mixed?

Have you ever seen this issue? I could understand a few points, but 35 points?

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2 Answers 2

up vote 6 down vote accepted

A number that big strictly sounds like mixing errors to me. Stratification of warm wort and cold top off water happens a lot. You need to shake vigorously anyway to get some aeration into the fermentor. Take your gravity readings after that step in the future.

Also, if you used 2.5 gallon of water for the boil and 3 gallons to top off, what happened to the water that evaporated during the boil?

I suspect the additive errors with mixing and stratification have given you the wrong reading.

Also, be sure to twirl the hydrometer in the testing sample after it sits a bit. This gets air bubbles and floating debris off the hydrometer. These, too, can falsify your reading.

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My cooled wort was at 77F. My top-off water was at 70F. Not identical, but not too dissimilar. I did twirl the hydrometer in the solution. I lost about 0.5 gallons during the boil. My pot is 12" in diameter and The water level dropped 1.25". That comes out to about .48 gallons. This means 5 gallons of water made it into my fermenter, right? –  JackSmith Mar 1 '10 at 15:53
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I did not shake the carboy after topping off to mix everything. I've never done this. I think I'm realizing every reading I've ever taken has been wrong because of this, but they were always in the expected range. Here's how I aerate: poor the cooled wort through a funnel into the fermenter. This splashes like made and the wort foams up about 3". I the pour spring water from their bottles into the carboy. I pour about a quart in, it splashes, I re-cap the bottle, shake the hell out of it, pour in about half of what remains, cap it, shake it, pour the rest. I do this with all the bottles –  JackSmith Mar 1 '10 at 15:56
    
I mean every original reading I've taken was wrong. Obviously post-primary readings would be accurate because the churning motion of the primary fermentation thoroughly mixes everything. –  JackSmith Mar 1 '10 at 18:15
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That does seem strange. If you didn't mix in the spring water well then that is most likely the culprit. You could have collected a sample from the more dense portion of the wort. Off the top of my head here are a few other things that could create (usually small) changes in OG readings:

  • Did you do a temperature correction for your wort gravity reading? If your hydrometer is calibrated at 60 F, then your sample needs to be 60 F, or you have to do a correction.
  • Did the recipe actually call for LME, but you used DME instead?
  • Check the recipe - Maybe the recipe is for 6 gallons in the kettle, 5.5 gallons in the fermentor (minus trub) and 5 gal finished beer. So you could have brewed a slightly smaller batch than the recipe called for.
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Thanks for the answer. Some follow-ups: (1) The temperature correction between 60F and 72F (where I measured) is 0.0013. If I took it into account, my reading of 1.090 would be standardized to 1.0913 - slightly higher, even. (2) The recipe (Magic Hat #9 from CloneBrews) definitely calls for 5.5lb light DME and 0.5 lb wheat DME. This is what I used. (3) The recipe is for a 5 gallon yield, partial volume boil topped off to 5 gallons in the fermenter. –  JackSmith Feb 28 '10 at 22:38
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