Grain Absorption While Squeezing

[JohnSand]

I generally ballpark my water volumes. When I used a 5 gallon pot for 5 gallon batches, I always topped off. It was easy to take a gravity and do the math. Now I have an outdoor burner and a bigger pot. I guess-timated it today, and was close. I can adjust based on today's numbers, and I will. But if you use an online calculator, and squeeeeze, what value do you use for grain absorption?

 

[pricelessbrewing]

I use my own calculator, in my signature below, and all my default values are on there.

The default grain absorption rate for my calculator is 0.08 Gal/lb.

 

[JohnSand]

I noted that. After I posted, I did some quick math and came up with a similar number. You squeeze?

 

[DurtyChemist]

0.125. Use that and you'll either have the correct amount or more.

 

[pricelessbrewing]

0.125. Use that and you'll either have the correct amount or more.

Have to disagree with this one. 0.125 gal/lb is the typical absorption rate for a mash tun setup with no draining or squeezing. You'll be over your estimated volume if you use that for a BIAB setup.

 

[chickypad]

I get .125 with regular tun, .09 with BIAB and squeeze.

 

[JohnSand]

Thanks Chemist, but I think Priceless has it right for squeezing the bag. I put the grain bag in a colander with a plate on it and lean my considerable weight on it.

 

[Devin]

I use .075 after several BIAB brews and seeing how much I lost to the grain. That is my average. I have gotten better and I have gotten worse. I squeeze the bejeebus out of the bag with pan lids and then I do a twist squeeze with the bag.

 

[doug293cz]

In an experiment I reported here I got a BIAB grain absorption of 0.09 gal/lb by suspending the grain bag above the BK for 10 minutes with no squeezing. I then squeezed aggressively, and reduced the grain absorption to 0.06 gal/lb. Priceless' default of 0.08 gal/lb is reasonable for a moderate squeeze.

You should make measurements on your own system, with your process, if you want to get a more precise number to use in your calculations.

Brew on

 

[pricelessbrewing]

In an experiment I reported here I got a BIAB grain absorption of 0.09 gal/lb by suspending the grain bag above the BK for 10 minutes with no squeezing. I then squeezed aggressively, and reduced the grain absorption to 0.06 gal/lb. Priceless' default of 0.08 gal/lb is reasonable for a moderate squeeze.

You should make measurements on your own system, with your process, if you want to get a more precise number to use in your calculations.

Brew on

This.

0.08 seems to be commonly used, and it has held up to be pretty accurate in my method. Everyone will have slightly different average values though.

 

[DurtyChemist]

Have to disagree with this one. 0.125 gal/lb is the typical absorption rate for a mash tun setup with no draining or squeezing. You'll be over your estimated volume if you use that for a BIAB setup.

Yes you will have more wort than you would with using a number such as 0.08 qt/lb. Using 0.08 qt/lb on a 15 lb grain bill is 1.2 quarts absorbed. using 0.125 on a 15 lb grain bill you get 1.875. less than half a quart difference between using the two numbers but using 0.125 qt/lb grain you'll have that extra wort in your pot. For this reason I suggested using the standard 0.125 value. It's always better to have more wort than less.

 

[chickypad]

Yes you will have more wort than you would with using a number such as 0.08 qt/lb. Using 0.08 qt/lb on a 15 lb grain bill is 1.2 quarts absorbed. using 0.125 on a 15 lb grain bill you get 1.875. less than half a quart difference between using the two numbers but using 0.125 qt/lb grain you'll have that extra wort in your pot. For this reason I suggested using the standard 0.125 value. It's always better to have more wort than less.

It's gallons not quarts. You're talking about a .675 gal difference which is not insignificant. I never use the standard when doing BIAB. That looks like a nice calculator from priceless, I will just change it to .09 which has been very reproducible for me (I'm not the strongest squeezer).

 

[DurtyChemist]

It's gallons not quarts. You're talking about a .675 gal difference which is not insignificant. I never use the standard when doing BIAB. That looks like a nice calculator from priceless, I will just change it to .09 which has been very reproducible for me (I'm not the strongest squeezer).

if you have found that 0.09 is perfect for you that is fine. I'm saying if you use 0.125 yo will always be ahead whereas using 0.08 you would be behind when measuring wort. If you use the math that says grain absorbs more than you expect you are being conservative and you'll be closer to your numbers. Until you actually weigh the amount of water your grain absorbs with your crush after your mash you cant take anyone's advice of what number to use because each brew-house is different. This was my point. Using 0.125 will BENEFIT you whereas using 0.08 found in other brew-houses will hurt you.

 

[pricelessbrewing]

if you have found that 0.09 is perfect for you that is fine. I'm saying if you use 0.125 yo will always be ahead whereas using 0.08 you would be behind when measuring wort. If you use the math that says grain absorbs more than you expect you are being conservative and you'll be closer to your numbers. Until you actually weigh the amount of water your grain absorbs with your crush after your mash you cant take anyone's advice of what number to use because each brew-house is different. This was my point. Using 0.125 will BENEFIT you whereas using 0.08 found in other brew-houses will hurt you.

I'd rather sparge up to the proper pre boil volume than boil down to it and waste time and propane.

 

[doug293cz]

if you have found that 0.09 is perfect for you that is fine. I'm saying if you use 0.125 yo will always be ahead whereas using 0.08 you would be behind when measuring wort. If you use the math that says grain absorbs more than you expect you are being conservative and you'll be closer to your numbers. Until you actually weigh the amount of water your grain absorbs with your crush after your mash you cant take anyone's advice of what number to use because each brew-house is different. This was my point. Using 0.125 will BENEFIT you whereas using 0.08 found in other brew-houses will hurt you.

Weighing the bag to determine water absorption is not as easy as it appears. The grain loses a lot of weight (as sugar) into the wort. So if you start with 10 lbs of grain, the spent grain would weigh much less than 10 lbs if dried after mashing. Just weighing the bag with wet grain, and subtracting the weight of the original dry grain, will seriously underestimate the weight of the water absorbed. To get accurate absorption by weighing, you have to correct for the weight of the sugar extracted from the grain.

A better way to determine the amount of water absorbed is to carefully measure the volume of strike water, and then carefully measure the volume of wort collected before any sparging. The absorbed volume is then strike volume minus wort volume (this assumes mashing in the BK, so there is no dead volume like with a MT.) This is still not totally rigorous, as 1 gal of wort will contain a little less than 1 gallon of water. But it gives the correct result needed for strike water volume calculations.

Brew on

 

[Mer-man]

I got .065 gallons per pound of absorption with serious squeezing. Next time I will give it a 10 minute hang and see what that gets me before squeezing.

 

[JohnSand]

Thanks.

 

[ultravista]

Resurrecting the dead - any updates?

 

[Murphys_Law]

I'm at about where priceless is for a soft squeeze. Maybe a little better if I'm pissed off at the world and squeeze like it smoked my last good cigar.

 

[TomVA]

I think the grain absorption depends on the mash thickness, amount of grain, and how hard you squeeze. I do BIAB with full water volume and carefully measure the volumes of the strike water and pre-boil wort with a calibrated ruler, and adjust both for temperature to 70°F. My last 7 batches averaged 0.04 gal/lb and ranged from 0.035 (for 7 lb grain bill) to 0.05 (for 2 lb grain bill).

I squeeze the bejesus out of the hot grain bag after 5 minutes of draining, leaning all of my weight onto a metal bowl on top of the bag in a metal colander (never use glass!). Sometimes I even stand on the bowl! Brewhouse efficiencies average 80%.

TomVA

 

[pricelessbrewing]

0.035? Sorry, I just don't buy it.

 

[Sadu]

I get the same efficiency whether I squeeze or not, typically 80-85%. If my preboil volume is a bit low just pour a bit more water through the grain. Squeezing used to be my least favourite part of brew day, now I don't bother.

 

[TomVA]

0.035? Sorry, I just don't buy it.

Actually my best batch so far was 0.037 gal/lb, i.e.0.26 gals loss for 7 lbs of grains (the 0.035 was an extrapolation on my graph for a 10 lb grain bill). The two prior batches were 0.040 and 0.038 gals/lb.

I calibrated my 8 gallon brew kettle by weighing one gallon increments of room temperature water into it (8 lbs, 5.25 oz per gallon @ 70°F) up to 5 gallons, and carefully measuring the depth for each gallon increment. With care, practice, and a flashlight I can read the water level to the nearest 1/32nd of an inch on my stainless steel ruler, which for this kettle equals 0.02 gal. The average of the depth changes for the last four increments gives me a factor for the kettle. (The first depth at one gallon is disregarded since there is a slight curve at the bottom of the otherwise straight wall kettle). I have been doing this kind of calibration for many years for my tomato canning and it is accurate.

After squeezing my grains and combining the wort, I stir well and then measure the temperature and wort depth. The depth gives me the gallons of wort at the hot temperature per the calibration above.

I then adjust this volume to 70°F (same as the original strike volume) by multiplying the hot volume by the ratio of water density @ wort temperature over the water density at 70°F. Since the strike water volume is measured by the same method, the difference is what matters as opposed to the absolute volume.

Assuming each reading could be off by +- 0.02 gallons, the difference of the two readings could be off by 0.04 gallons, so my 0.037 reading could have been as high as 0.042, but still a far cry from 0.08 or 0.12.

Yes I know I am anal, but when you stand on a bag the grains come out pretty dry.

TomVA

 

[doug293cz]

Actually my best batch so far was 0.037 gal/lb, i.e.0.26 gals loss for 7 lbs of grains (the 0.035 was an extrapolation on my graph for a 10 lb grain bill). The two prior batches were 0.040 and 0.038 gals/lb.

I calibrated my 8 gallon brew kettle by weighing one gallon increments of room temperature water into it (8 lbs, 5.25 oz per gallon @ 70°F) up to 5 gallons, and carefully measuring the depth for each gallon increment. With care, practice, and a flashlight I can read the water level to the nearest 1/32nd of an inch on my stainless steel ruler, which for this kettle equals 0.02 gal. The average of the depth changes for the last four increments gives me a factor for the kettle. (The first depth at one gallon is disregarded since there is a slight curve at the bottom of the otherwise straight wall kettle). I have been doing this kind of calibration for many years for my tomato canning and it is accurate.

After squeezing my grains and combining the wort, I stir well and then measure the temperature and wort depth. The depth gives me the gallons of wort at the hot temperature per the calibration above.

I then adjust this volume to 70°F (same as the original strike volume) by multiplying the hot volume by the ratio of water density @ wort temperature over the water density at 70°F. Since the strike water volume is measured by the same method, the difference is what matters as opposed to the absolute volume.

Assuming each reading could be off by +- 0.02 gallons, the difference of the two readings could be off by 0.04 gallons, so my 0.037 reading could have been as high as 0.042, but still a far cry from 0.08 or 0.12.

Yes I know I am anal, but when you stand on a bag the grains come out pretty dry.

TomVA

Now that you have described your calibration and measurement method, I'm much more inclined to believe your grain absorption rate numbers. You're doing everything right. Like @pricelessbrewing , I was very skeptical initially. Seems you are a world class squeezer.

Brew on

 

[pricelessbrewing]

Actually my best batch so far was 0.037 gal/lb, i.e.0.26 gals loss for 7 lbs of grains (the 0.035 was an extrapolation on my graph for a 10 lb grain bill). The two prior batches were 0.040 and 0.038 gals/lb.

I calibrated my 8 gallon brew kettle by weighing one gallon increments of room temperature water into it (8 lbs, 5.25 oz per gallon @ 70°F) up to 5 gallons, and carefully measuring the depth for each gallon increment. With care, practice, and a flashlight I can read the water level to the nearest 1/32nd of an inch on my stainless steel ruler, which for this kettle equals 0.02 gal. The average of the depth changes for the last four increments gives me a factor for the kettle. (The first depth at one gallon is disregarded since there is a slight curve at the bottom of the otherwise straight wall kettle). I have been doing this kind of calibration for many years for my tomato canning and it is accurate.

After squeezing my grains and combining the wort, I stir well and then measure the temperature and wort depth. The depth gives me the gallons of wort at the hot temperature per the calibration above.

I then adjust this volume to 70°F (same as the original strike volume) by multiplying the hot volume by the ratio of water density @ wort temperature over the water density at 70°F. Since the strike water volume is measured by the same method, the difference is what matters as opposed to the absolute volume.

Assuming each reading could be off by +- 0.02 gallons, the difference of the two readings could be off by 0.04 gallons, so my 0.037 reading could have been as high as 0.042, but still a far cry from 0.08 or 0.12.

Yes I know I am anal, but when you stand on a bag the grains come out pretty dry.

TomVA

Fair enough. That's exactly how I take my measurements as well, but the lowest I've gotten was 0.06 gal/lb at that was when leaning down onto the bag pressed into a colander with almost all my weight on it (typically 14-16 lb grist).

 

[TomVA]

I typically make 2.5 to 3.5 gallon batches of beer using 5 to 7 pounds of grain, which may be why I can squeeze it so well.

TomVA