I realize your not trying to trick anyone I'm just trying to get my head around how different the absorption rate is. I do let my grain sit over a bucket for the whole boil after sparging and I seem to get maybe another litter out of the spent grain. So grain and grain crush does make a huge difference in absorption rates.
I use a crankenstein 3 roller mill but can't remember the crush. Might try order some off Mark and see what I get. Ide love to not have to sparge those 3 extra litters. Thanks for the info.
I have a 20 litre unit and I find I am getting grain absorption figures similar or even a bit less than what mikk is quoting.
When I was setting my unit up in Beersmith I was having trouble so I measured everything as I went over 5 or 6 brews to find where that extra wort came from.
I have a 3 roller Crankenstein mill and I have set my gap to 1.4mm and with this I get an efficiency at the mash of 77% on a 1050 beer.
I found in Beersmith by selecting BIAB Mash with a full boil in the Mash Profile window rather than selecting the Sparge Options it corrected the total water amount to reflect the true grain absorption rate.(in my system)
I then went into Beersmith - tools - options - advanced - and fine tuned the grain absorption to suit my system. It is set by default on BIAB at 0.586 and 0.960 on the standard grain absorption setting. Anyone choosing to do this can set this figure to accurately represent their own brewery figures.
I am almost sure it has everything to do with the crush as I have spoken to other users of BM's and some are not reporting this descrepancy
I have also noticed a very slight difference when I used Marris Otter malt compared to Wyermanns Pils but not enough to worry me. I guess it is the difference in the husk in this case.