BIAB -- Calculating total water needed

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BarberSurgeon

BarberSurgeon

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I'll be brewing up my first AG BIAB tomorrow. I'm making a two-gallon batch with 4.2 pounds of grain. Beer Smith suggests I use 6.56 qts of water for the mash then sparge with 1.37 qts (I may not sparge). I understand that boil-off will vary with temperature, climate, and altitude, but how much can I expect the grains to absorb? There seem to be so many factors to consider just to get down to 2 gallons. Please help!
 
I believe .13 gallons per pound of grain is a reasonable estimate until you take actual readings from your rig. That would be about .5 gallons for your recipe.
 
I don't want to discourage you but 2 gallons is hardly worth the effort. Can't you do more? Surely you can find some food grade plastic buckets for free or cheap. There has to be a commercial bakery that buys molasses or corn syrup in buckets in your area. It's food grade and often thrown away.

I would not invest anytime in making less than 4.5 gallons... a 5 gallon batch will yield 4.5 gallons or a slightly more...depending on carboy space etc...


Here is a basic article on the process...Have fun.

Stovetop All Grain Small Batch Brewing - Lustreking Brewing
 
OldWorld said:
I don't want to discourage you but 2 gallons is hardly worth the effort. Can't you do more? Surely you can find some food grade plastic buckets for free or cheap. There has to be a commercial bakery that buys molasses or corn syrup in buckets in your area. It's food grade and often thrown away.

I would not invest anytime in making less than 4.5 gallons... a 5 gallon batch will yield 4.5 gallons or a slightly more...depending on carboy space etc...


Here is a basic article on the process...Have fun.

Stovetop All Grain Small Batch Brewing - Lustreking Brewing
Click to expand...

I'm sure your advice is sound and great coming from your situation, but I've been making 2 gallon batches of extract for months and love it. It's practical, fast, and I get to try a lot of different recipes in quick succession. I started on 5 gallons and just hate the maintenance, cleanup and having to drink that much of the same beer.
 
I'd disagree that a small batch isn't worth making. Less product for the same amount of time/effort, fine, but I see a lot of advantages to a smaller batch size.

My first BIAB I was almost a gallon short post boil because I underestimated how much water the grain would absorb. With the smaller batches the absorption factor will make a bit difference in final volume, so I'd personally be paying attention to those numbers. Other than that I'm still working out the kinks in the process myself.
 
I use 0.09 gallons per pound of grain for absorbtion. I don't squeeze the bag, I put it in a strainer over the boil kettle and let it drip for 10 minutes. I measured the absorbtion for the first few batches so I'd have a good number for my system. I don't sparge and get a pretty consistent 65% efficiency into the boiler. As far as boil off, 1.25 gallons an hour would be a good guess until you can measure it. Enjoy your brew day.
 
Seven said:
This may help you: BIAB Water Volume Calculator
Click to expand...

Definitely looks like a good start. This calculator suggested I strike with 3.53 gallons (assuming no sparge), with .53 going to the grains and 1 gallon to boil-off.

I'm boiling up a gallon in my kettle now to see how much I lose in a half hour. The first link claims that if I multiply the loss by two, I should get an approximate boil-off rate.
 
Okay, is this even possible? I just measured a 33% (1/3) boil-off in 30 minutes in my one-gallon system test. I am no expert on the physics behind this stuff, but does that mean I'll lose 2/3 of my starting volume over an hour? That seems crazy. This is by no means my first boil, and I've never lost that much before. I'm guessing there are other factors such as head space and kettle-volume to water-volume ratio that affected this measurement...
 
It takes a specific amount of heat added to boil off a gallon of water. I'm too lazy or I could look it up but to lower the amount you boil off, you reduce the amount of heat added. You want a good boil to drive off the DMS precursors and isomerize the hop oils but it seems to me that you are getting a more vigorous boil than needed.
 
Thanks. That does make sense. I left the electric burner on high, so perhaps just maintaining a rolling boil on a medium setting is all I need (and what I normally do).
 

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