Low OG

[Cousin Brewy]

I got a real puzzling question. Thanks in advance for any help... today I took a shot at a baltic porter. 21 pounds grain bill and it SHOULD have yielded an og in the high 1.080's at least, but I'm lucky to have gotten 074 and that was continuing my boil from 60 min to 105 min. I collected about 8 gallons of wort and took it down to about 5-5.5 gallons.
Mashed for 1 hour at 153. Is it possible that I sparged too much, diluting the wort??

 

[Nosybear]

Did you use the default efficiency? If so, it's likely you got exactly the OG you should have. The higher the gravity, the lower the efficiency. I've never seen a mathematical model of the efficiency decrease but it is real.

 

[Pricelessbrewing]

Did you use the default efficiency? If so, it's likely you got exactly the OG you should have. The higher the gravity, the lower the efficiency. I've never seen a mathematical model of the efficiency decrease but it is real.

The relationship between the various types of efficiency, and the amount of grain used per volume of wort is definitely real.

I derived the formulas for the relationship from first principles and put it up on my calculator, https://pricelessbrewing.github.io/BiabCalc/#EfficiencyEvaluation. The predicted numbers match braukaisers batch sparge prediction formulas, and I've taken detailed notes of all of my brew and the corroborate. Scroll down and you'll see a chart. You can even change it to exactly fit your system and get a pretty accurate prediction for the efficiency for any recipe, or making a change to your process and get very close to your OG.