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Where oh where did my gravity go?

Pre-boil gravity was 1.048 and 7.5 gallons in the kettle. Boiled for 60 minutes and final volume was 6 gallons. My gravity of my wort just before pitching was 1.053. I left about 0.5 gallons in the kettle (included in the 6 gallons). My target was 1.060 which is about where it should have been after boil off. It is possible that there could be wort stratification? I thought that was only a extract thing.

Any thoughts?

Sounds like you have a measurement error somewhere along the way. Either your pre-boil, post-boil gravity measurements are off, or you volume measurements are off. I would guess it is your volume measurements. Is it possible you are a quart off on each of them? If so that would leave you 3/4 gallons off and would account for the missing gravity taking into account the preboil, losses in the kettle and in the fermenter.

I suppose it’s possible because i was doing volume readings with my sight glass which isn’t the most precise method but here is why I doubt that: my system has never had less than 1.3 gallons of boil off per hour and is usually around 1.5 gallons per hour. So even if I misread my first reading by 1/2 gallon (making it 8 gallons) that would only be a boil off of 0.75 gallons to get from 1.048 to 1.053. I know I lost more than a gallon to boil off.

I’m completely stumped. The grain bill was:

10lbs 2row
1.25 lbs C80
10oz roasted barley
10oz chocolate

1.048 is about 78% conversion efficiency which is around what i usually get so this number seems more believable. This just leaves the post boil measurement in doubt which was why i wondered if wort stratification was possible with an all grain brew. I didn’t think it was but I wanted to verify.

Temperature effects? You’ll get very low readings at very high temperatures. Might need some temperature adjustments to compare apples to apples.

My readings were temp corrected. I took the pre-boil sample at about 55 degrees and was about 1.049. My post boil reading was taken right before pitching at about 64 degrees.

I’m not sure if this makes a difference but I took the sample for pre-boil and put it in the freezer for about 20 minutes to cool it down.

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