Thinking about doing the following.
Brew 1: Imperial IPA
Mash 21lbs of grain for 90 minutes at 151 using 7 gallons
Sparge with whatever is needed to get me 7 gallon total into boil kettle. Assuming 50% Efficiency I get an S.G of 1.079.
(Using same grain bed)
Brew two: Baby IPA
Then Sparge 7 gallons at 170 for 15 minutes
Sparge again till 7 gallons in boil kettle
Assuming 75% Efficiency I get about half the first brew or 1.040
Does anyone have any thoughts on doing this? Also, I usually get between 75% and 80% Efficiency, but I have never calculated runnings. Does the 50% Efficiency make sense on the first brew?