Hot answers tagged efficiency
Are you sure your calculating your 100% correctly? Or more importantly have you measured your collected volume precisely this can through off your calculation significantly too. I batch sparge as well. Once I have all my wort collected I start my burner, give it a quick stir and take an immediate sample for preboil gravity. It doesn't take much of a stir ...
A refractometer helps too, since you don't need to adjust for temperature and can use a very small sample. I normally rack the wort before I take a reading (and measure volume) which helps to evenly distribute the sparge and first runnings.
It's best to measure as the wort comes to the boil for the reasons you mention - all the wort is at the same temperature and the convection currents have mixed the wort fully, so you get a much more accurate reading.
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