What's The Best Way To Post Efficiency On Ahb?

[Gulf Brewery]

....i always brew full( 2x23 ltr) batches , so i have Batch size set to 46 ltrs and wort size set to 36 ltrs. With my system i boil 48 ltrs down to 36ltrs (39ltrs minus 3ltrs trub/hop crap etc) over 90 mins. Then i add 10 ltrs refridgerated water (helps get pitching temp lower)to fermenters to get 46ltrs. Does this mean i should set Batch size to 36 ltrs..???

Hargie

I think your batch size is 36 litres and your promash figures should be based on what you get after the boil and before dilution.

Cheers
Pedro

 

[bayWeiss]

Ref Kunze; Technology Brewing and Malting
Hot Break is typically about 1.42 Kg/100 L
Cold Break about 0.22 Kg/100 L

Just a quick play with the numbers (I realise that there are some other factors, but I think they are below the resolution of the measuring equipment in use)
Total break material ~1.64 Kg/100L,
If the sweet wort was say 1.050
You loose from the solution about 1.42g/L on Boiling and another 0.22g/L on Cooling a total of 1.64g/L.
So you loose some apparent density, the true value for the sugar content of the sweet wort should be ~1.04836, rather than 1.050.
0.05-0.04836 = 0.00164
(0.00164 / 0.050) X 100 = 3.28%

About a 3.3% apparent loss in efficiency; caused by break formation.

Break once it forms can't be stirred in and measured; it has come out of solution, it has no more effect on the gravity reading than would a teaspoon of sand in the bottom of your hydrometer tube.
Even if it's stirred into suspension, it won't affect the gravity reading.

MHB

This makes perfect sense. It is so logical, but somehow the computer in my head did not think about it. LOL. Add this on top of reasonable measurement/equipment error, and it seems like one could easily measure an efficiency with a value of of -5% or so of their pre-boil OG. This is one more reason why I believe only Pre-Boil Efficiencies should be referenced, and not post-boil.