12 points for 5 gallon brew that was corrected with 1/2 boil off? Is that correct? 10% of the liquid affected almost 25% of the sugar?
Perhaps an ignorant analysis on my part: would the temp affect the measurements on a Refractometer? I know that using a hydrometer is affected by temp. Sorry if this is annoying.
I wanted to report back that I hit between 70-75% for beer made this past week. I did not condition it, and it was milled once. Now I'm thinking I should mill it twice for BIAB. I was supposed to hit 1.066, and I hit 1.060, though one batch was 1.058. I used a free calculator that said I could hit anywhere from 1.059-1.069 with 75% efficiency.
Nah, you read that wrong. Or I wasn't clear enough.
Est Pre-Boil Vol: 12.52 gal
Meas Pre-Boil Vol: 12.70 gal
Est Pre-Boil Gravity: 1.043 SG
Meas Pre-Boil Gravity: 1.031 SG
So, came out of the mash tun 0.2 gallons too much (typical for me) and 12 points low (not typical).
I then extended the boil from 60 minutes to 88 minutes, pushing all hop additions back 28 minutes to retain the same profile. So, instead of boiling off 1.50 gallons, I boiled off 2.20 gallons. How'd I come up with 28 minutes? Kept checking the gravity every 5 minutes as it boiled until I hit 1.043 SG (see above), then I started the 60 minute timer. That just happened to be 28 minutes.
Est Batch Size: 10.50 gal
Meas Batch Size: 10.00 gal
Est Original Gravity: 1.051 SG
Meas Original Gravity: 1.051 SG
Refractometers are indeed affected by temperature, but this one is ATC. I take my samples by stirring the brew kettle vigorously with my stainless mash paddle, then dripping the liquid that drips off the paddle onto the refractometer lens. Yes, it's 160F-212F liquid.
Leave the refractometer cover open for 30 seconds to allow the liquid to cool, per the manual. Those few drops of liquid cool very rapidly. Close the cover, read the gravity. Works every time. This was the third time I've compared my refractometer to one of my hydrometers, and every time they've been within 1 point of each other using this method.