A while back I found a website with a table of how much second runnings to add while batch sparging to hit your target pre boil gravity. I know the texts say to use the same amount of sparge water as mash water, but I like to take the gravity and volume of my first running, take the gravity of the second running, then add the right amount to get my pre boil gravity on target, and adjust boil time to get the volume on target as well. Actually, if I nail the post boil gravity, volume is fine as long as it's close or a little over. Has anyone here seen a table like this? Thanks.