Forumula for Water Absorption

Okay, I've seen several formulas for this

I've read that grain can hold roughly its weight in water.  With water weighing 8.35 lbs  one way of calculating the water absorption would be to divide the grain weight by 8.35

I've also been told that water absorption is between .1 - .2 qts per lb of grain (I don't like that because its a huge difference between .1 and .2)

I've also been told that multiplying .125 * the grain weight will give you your amount of water absorption. 

Can anybody tell me if any of these are correct or commonly settled on? 

" You have to remember that the weight of the grain going into the mash is not the same as the weight of the grain that went into the mash. During mashing, sugar and protein is extracted from the grains, and that leaves them as shadows of their former selves. It is safe to assume that the postmash grain mass is about 40% of the weight of the grain you added."

" If you mash 10 pounds of grain it will weigh about 4 pounds when you are finished. Since this 4 pounds is 20% of the weight of the spent grains, the weight of the water will equal 4 times the weight of the grain (80% divided by 20% equals 4). You will lose 4X4 pounds, of water in the spent grains. Since water weights about 8 pounds per gallon, this equals 2 gallons."

Wish I could take credit but all credit goes to Ray Daniels, Designing Great Beers

I hope it helps

Jeff

jharle2 said:

" If you mash 10 pounds of grain it will weigh about 4 pounds when you are finished. Since this 4 pounds is 20% of the weight of the spent grains, the weight of the water will equal 4 times the weight of the grain (80% divided by 20% equals 4). You will lose 4X4 pounds, of water in the spent grains. Since water weights about 8 pounds per gallon, this equals 2 gallons."

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To be honest with you, its a little confusing.  Specifically that second sentence I put in bold.  It says that the 4 lbs is 20% of the spent grain?  How can this be, if the spent grain now weighs 4 lbs isn't 4lbs 100% of the spent grain?  At the very least it is 40% of the initial grain weight, I'm not seeing where the 20% is coming from? 

Wildrover said:

Can anybody tell me if any of these are correct or commonly settled on?

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YES ;D

I've read that grain can hold roughly its weight in water.  With water weighing 8.35 lbs  one way of calculating the water absorption would be to divide the grain weight by 8.35
I've also been told that water absorption is between .1 - .2 qts per lb of grain (I don't like that because its a huge difference between .1 and .2)
I've also been told that multiplying .125 * the grain weight will give you your amount of water absorption.

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I believe BeerSmith uses .125 which is what I go by. All three are correct as long as you remember there will be a variance. Type of grain/adjunct, and time in the water are factors in the grain to water variables. I believe the variance is malted vs. unmalted grains vs. adjuncts. Some will soak up water faster than the others.

Clear as mud right?

Cheers
Preston

Sorry that it sounds confusing. I went back and checked the wording and what I wrote is pretty much word for word out of the book. I feel the same way when reading these books on brewing. I too use Beersmiths calulations. Something else that may help is a simpe equation I have used also from Ray Daniels:
Grain weight in lbs. x 0.2 equals Gallons of water retained by grains

Good Luck
Jeff

jharle2 said:

Sorry that it sounds confusing. I went back and checked the wording and what I wrote is pretty much word for word out of the book. I feel the same way when reading these books on brewing. I too use Beersmiths calulations. Something else that may help is a simpe equation I have used also from Ray Daniels:
Grain weight in lbs. x 0.2 equals Gallons of water retained by grains

Good Luck
Jeff

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I like this one a whole heck of a lot better 

That being said, lately I've been calculating the water absorbed using all the three formulas (well four if you count the .1-.2 as two) to see which one gets me closer.  So far, as Preston alluded to, it all depends.  Sometimes its the weight of grain in lbs/8.35 sometimes its the .125 and so on and so on.  Interesting though