Hello, My last four or five batches I've had the same problems with my post boil gravity, it's coming in way too low.

For instance, I made Jamil's Hoppiness is an IPA and the post boil gravity is supposed to be 1.082, and comes in at 1.055. The odd part is that my pre-boil gravities are almost spot on. I have a vigorous boil, go from 7.3 gallons to about 5.5 post boil. I don't understand how this might be happening...any help would be appreciated!

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"Gozer"

Did you calibrate your refractometer or hydrometer?

I would bet your preboil is off too, definatley recalibrate.
Has your efficiency changed for some reason?

Thanks for the reply guys...yeah, I have verified my hydrometer...it is off....but only by +0.002.

I haven't made any changes....I have only been all grain for a little over a year, but my first half dozen batches were spot on. Perhaps I'm wrong, since I'm a noob....if my efficiency were off, wouldn't the preboil gravity be low?

How are you mashing and sparging?

How far off from your final gravity have you been for those last 4-5 batches?

I mostly fly sparge, but the last time I batch sparged, and the OG remained comparable.

FG's have been coming in typically lower...last batch was 0.007 lower. I let the fermentation go a full 3 weeks, and the only time I test the OG is right before I keg. I'm a bit paranoid about infecting the wort, and I've not found a good way to pull the wort for OG testing. So theoretically, I could have stopped and kegged earlier so the FG isn't too low. But the beers come out awesome...so do I just accept what I'm getting and move forward? I'm a bit of a perfectionist....if the recipe says 1.082, I'd like to get at least close.

I have been bouncing around the idea of getting a refractometer....thots?

How are you obtaining your sample for the pre-boil and post-boil readings? At least one of them is wrong, and if you are sure your instruments are accurate, then you are likely not taking a representative sample of a homogeneous wort.