So I brewed my second all grain batch yesterday and tried to measure my system's efficiency. Got a couple questions.
Original BK volume was 7.5 gallons, slightly higher than I wanted due to a slightly miscalculated mash volume on my part. I boiled down the 7.5 to 7 gallons and started into my 60. To the BK gravity was 1.055, OG was 1.070 and I ended up with 6 gallons to the fermenter. It shouldn't matter, but just in case, I used 13.25lb of grain and 9 gallons of water in a single infusion mash with a batch sparge. My question. Do I calculate from the original BK volume or the boiled down volume? As in, did I achieve ~88% efficiency or ~82% efficiency. I'm kind of glad I used more volume...as it stands, I'm 10 points above the recipe calculated at 70%!
Second question. My first runnings hit 1.095, my second runnings were at 1.050. Final pre-boil gravity ended up 1.055. I measured at vorlauf in both mash/sparge stages and straight from the kettle was used for the pre-boil measurement. Is this fairly typical? I was expecting more of an average between the two. I'm assuming that the gravity will be lower at the later stages of the sparge drain, bringing the overall pre-boil gravity down.
If you need other info, let me know.