Calculating the second runnings of a partigyle?

[NEKvt]

I recently brewed a blegian dark strong using the runoff from a single mash, and then added 5lbs of Pearl and pulled a second batch out of the tun.

I know my expected gravity at 75% efficiency from the first beer (I guess I also know any other percentage given that number), and I can add what the 5lbs of pearl would have added to that recipe.

My question is, if I wanted to recreate this second beer, what is my best route to figuring out the grain bill that I would use?

 

[LVBen]

Just use the same percentage for each grain, but scale it down to about 1/3 - 1/4 of the total. I assume you measured the gravity, so just scale it down to where 75% efficiency gives you the same gravity.

 

[NEKvt]

So if I hit 70% efficiency on the first runnings I should subtract 70% of each grain from the recipe?

That is what I originally did, but I get a result where my efficiency from the second runnings is ridiculously high. Guess I can just add equal percentages to each grain until I get to the gravity reading I found.