As title says, got my Anvil Foundry this weekend and brewed a quick batch of Cream of Three Crops to test it out. After reading a bunch of tips, I purchased the small batch adapter to use so it covered the side holes. Now I forgot to take a pre-boil gravity reading (whoops), I did have Pre and post volumes and post boil gravity of 1.053. From what I understand I can get a pretty good estimate of my pre boil gravity reading. For reference, I did a 90 min mash @152, with a 1 gallon sparge. So total mash volume was 6.75 gallons, with 5.5 gallons post boil.
Following this formula: Pre-boil Gravity = (((OG-1)* post-boil volume)/pre-boil volume)+1
This formula leads me to a pre-boil gravity of 1.039.
Plugging all the info in the various efficiency calculators from Brewer's friend gives me 81% give or take.
Am I missing something here? TBH I'm shocked at that high of efficiency cause when I was on my keggle outside I was barely hitting the 60s. Just want to make sure I am not crazy, especially with lots of discussion on various sites about efficiency issues with the Foundry.