Gravity question
 

Will a boil over cause a lower original gravity? Tracked well through the boil and I ended up lower than projected. Any input would be great. Thanks in advance.

Yes, it would. How much lower were you, and was your pre-boil gravity on target?

EDIT: This is assuming you still reach your original target post-boil volume.

Pre boil gravity was 1.040. I was trying to hit 1.070 but only hit 1.061. First time I had a boil over and am wondering if that's why. Thanks again.

Unless it was a big boil-over, I doubt that's the only contributing factor. I'd imagine your efficiency was also a bit lower than the recipe called for.

Also, btw, how much did you boil off? A gravity of 1.040 to 1.061 is a lot of boil-off!

Boil off was just over a gallon including the boil over. Apparently I need to take better care of my boil. Took my eye off and that's what happened.

Was this a 1.5-2 gallon batch? (just curious)

Also, can't say as to where I heard this but is it not ok to leave a lid on cracked during my boil to cut down the loss? I've heard it's not good to do that due to the hot break.

Nope it was a 6 gallon batch that is looking screwed up now. Nice!!

I don't see why it'd have an effect on hot break, but perhaps others know of a reason. The bigger concern to me would be DMS, produced during the boil, staying in the liquid. However, I'd imagine boil-off percentage is mostly all that matters in that regard. If you don't taste cooked corn in your beers I wouldn't worry about it.