What's the average grain absorption in BIAB brewing?

[Elysium]

I have been reading about different ideas and wondering what the grain absorption is if I'll mashing everything in the pot with a false bottom setup?

I even read in Ray Daniels' DGB book that it is at about 0.2 gallon per lb. Is it a good enough number to use to calculate how much mash water I need? (the reason why I am asking is simply because so far I have used a small 5 gallon system at home which was BIAB and I squeezed everything out of it, but soon I would like to brew on an industrial scale and need to start thinking differently).

If I calculate the percentage of the retained water in the spent grains....then it means 28% of the water will disappear after the mash when I throw away the spent grains. However.....I'll have 60% of the sugar retained from the grains in the pot. How does that affect the preboil size of the batch?

Cheers

 

[chickypad]

I'm not quite sure I understand your meaning of "BIAB with a false bottom set up" (are you squeezing the bag or just using it as an extra filter in addition to the false bottom?) Either way, 0.2 gal definitely doesn't seem right. I lose about .12 gal per lb in my tun with false bottom, about .09 gal per lb BIAB with squeeze, though I may be a bit on the wimpy side. Priceless has a BIAB calculator that is quite useful, he uses default of .08 gal per lb.

 

[Elysium]

I'm not quite sure I understand your meaning of "BIAB with a false bottom set up" (are you squeezing the bag or just using it as an extra filter in addition to the false bottom?) Either way, 0.2 gal definitely doesn't seem right. I lose about .12 gal per lb in my tun with false bottom, about .09 gal per lb BIAB with squeeze, though I may be a bit on the wimpy side. Priceless has a BIAB calculator that is quite useful, he uses default of .08 gal per lb.

Hey Chicky

Sorry...I have just edited my original post. Yeah... 0.08 seems to be okay. I calculated 0.78 too.Maybe there are other factors there too......equipment loss or something. No clue.

Thanks again for your thoughts.

 

[halcyondays]

I generally lose around a gallon of water for about 13lbs of grain, so 0.08 is about right on for me. I think the formula I saw in BYO a couple issues back had it at .079, so somewhere in that region. 0.2 is definitely high IMHO.

 

[daksin]

I think the rule of thumb for more traditional mashes is 0.1gal per pound, and I usually use 0.05 in my calculator. I squeeze the heck out of my bag, though.