It could be just this batch, then. Maybe the crush was different, or the amount of sparge water was different, or the mash pH was different if this batch used lighter colored grains than the last couple (or if the water used was different). It could be a number of things, if the first few batches were consistent.
Did anything change? Do you mill your own grain? Is this the same sized batch as the other batches?
Ok, so I did just about everything exactly the same. I do mill my grain. I bought a new monster mill about a month and a half ago, set the gap how I like it, and that's where it's stayed since. My batch size varies, but results are consistent. 3 days ago I brewed 12 gallons moose drool, 80% efficiency, hit target og, boil off was 2 gal over an hour, preboil and post boil were 10 points apart. The day before that I did 6 gallons witbier, 80% efficiency, about 2 gal boil off over 90 min, 10 point difference pre vs post boil. Week before Christmas I did 6 gallons of porter and 6 gallons Belgian blonde, 80% efficiency, 10 point difference over 60 min boil,target gravity on both. Couple weeks before that, 6 gallons Munich Helles 80% efficiency, all numbers hit. The only difference on this batch was the 1.5 tsp of gypsum that I added to the beginning of the boil. I don't see how that could have affected the gravity that much. This sounds like a dumb question, but can hops affect gravity? I wouldn't think it would, but this is the only batch it's happened with and it's an ipa.
It seems like whatever went wrong, happened in the boil. How did I screw up the easiest part of the process? Again, I'm pretty sure the mash was fine.
Even if I did everything wrong on this batch, I've done it exactly the same on the past 5, so I would expect the consistent results I've been getting.
