Grain Absorption

I just wanted some extra eyes on my math below, am I thinking about this correctly?

-Added 10.20 quarts of strike water to the mash tun, 6.05 pounds of grain.

-First runnings were 6 quarts.

-I calculated .10 gallons per pound of grain, which would be  (.605 gallons) 2.42 quarts of water absorbed.

So if I had zero dead space I should have collected 7.78 quarts. I ended up collecting 6 quarts. I think I failed to account for the quart or so of dead space in my 10 gallon Rubbermaid MT.

Outside of that, I would still be .50 quarts off. Not a big deal at all, but curious if I should up the grain absorption rate next time, or is it dependent on the amount of grain?

I calculate absorption at .12 and it’s accurate in my system. I think that’s part of the shortfall, and you may well have a little larger dead space number than you thought. Just keep taking good notes and soon you’ll reel in those numbers.

your water seems about right 1.5-2 qts of h20 per lb of grain. but i usually try to account for a little more absorption than expected.

as for absorption depends more i think i what type of grain and maybe how much. also maybe the size/shape of your mash tun could also be a factor. also how you mash in could be a factor…

+1 To taking notes and adjusting to your system. When I do biab .1 works, when I do larger batches with my cooler MT .12 works. That was all trial and error and keeping track. Dead space can easily be figured out by putting a measured amount of water in your empty MT, draining as normal and seeing how much less water you end up with.

Yeah I’m familiar with the dead space but when I was scooping out the spent grains this time there was more water above the false bottom then I’ve seen before. Would this still be consider dead space ?

It might be semantics, as long as you eventually account for all the loss in your sytem you can call it what you want. That being said part of it sounds like absorption: the grains prevented it from getting to your drain even if the liquid wasn’t permantly absorbed by the grains.