I brewed today . All grain robust porter. My target pre boil O.G was 1.046. I hit 1.050 I collected 7.5 gal. I loose about 2 gal an hr boilng. My target after boil was 1.061 and it was 1.059 . I’m trying to figure out why I’m over on the pre boil and under on the O G after boil , Any thoughts ?
Volume measurements or hydrometer calibration or reading gravity at different temps are the most likely reasons, but you’re only a couple points off, so it’s within the accuracy of most measurements anyway.