Originally Posted by Pilotpip
That's where I'm confused. I am measuring my volume and starting with the exact same pre-boil volume as I was when doing extract. I guess I'll up my strike water to compensate. So far I'm getting good (70-75%) efficiency out of no sparge so I'll hold off on that and maybe add a bit more to the strike water.
Interesting. If your pre-boil volume is the same, there are only a few places where the loss could be occuring.
1. Pre-boil measurement. If you measured your extract water at 6.5 gallons cold and your all-grain water at 6.5 gallons hot, then you would actually have more extract water (hot water expands).
2. Boil length and intensity. Assuming you are boiling for the same amount of time in the same pot, you might be getting more boil off with all grain because you are not taking the pot off the boil to add the extract (which also cools down the wort).
3. Trub. If you are using Irish Moss or Whirlfloc in the boil, you might be leaving more protein and hops trub in your boil kettle with your all grain brews than you were with extract.
Assuming all of your equipment and techniques are otherwise the same, those are about the only things I can think of to account for the loss.