Bag squeeze gravity test

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PhinneyWoodBrews

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Okay, so I know this subject has been hashed rehashed and beaten to death. However, a very recent discussion here about squeezing made me wonder about the gravity of the bag 'drippings' vs the gravity of the wort left in the kettle immediately after pulling the bag. Intuitively, I thought that the wort we squeeze out of the bag is not of significantly higher gravity than the main volume. Of course, I had to (rather unscientifically)test that out.

I brewed a 3.5g batch of an Oatmeal pale today, using 7lbs of 2-row and 12ounces rolled, quick-cooking oatmeal(cereal mashed prior to adding).

After the mash was complete, I pulled to bag and set it in a colander over a bucket. Refractometer reading for the main volume in the kettle was 1.074.
As the bag dripped more wort out(combo of gravity and squeezing), I tested the 'bag drippings" wort's gravity several times with the refractometer. Subsequent readings were identical to the main volume gravity, excepting the last-rather viscous-bit I squeezed at the end, which was about 1.077. Of course, the volume collected towards the end was a couple ounces-I would say not enough to budge the needle on overall gravity after adding. If one is most interested in hitting volume into the fermentor numbers, squeezing every last bit out is important-especially if you're adding top off water(as I sometimes do-still dialing in my boil off rate). If you're more interested in hitting your target gravity--those last precious ounces of wort aren't really doing much i.e it's not a high gravity syrup that's going to boost your OG much. Does that make sense? Did I forget something and my conclusion is off-base? I'm sure you'll let me know.
Cheers!
 
Last edited:
PhinneyWoodBrews said:
Okay, so I know this subject has been hashed rehashed and beaten to death. However, a very recent discussion here about squeezing made me wonder about the gravity of the bag 'drippings' vs the gravity of the wort left in the kettle immediately after pulling the bag. Intuitively, I thought that the wort we squeeze out of the bag is not of significantly higher gravity than the main volume. Of course, I had to (rather unscientifically)test that out.

I brewed a 3.5g batch of an Oatmeal pale today, using 7lbs of 2-row and 12ounces rolled, quick-cooking oatmeal(cereal mashed prior to adding).

After the mash was complete, I pulled to bag and set it in a colander over a bucket. Refractometer reading for the main volume in the kettle was 1.074.
As the bag dripped more wort out(combo of gravity and squeezing), I tested the 'bag drippings" wort's gravity several times with the refractometer. Subsequent readings were identical to the main volume gravity, excepting the last-rather viscous-bit I squeezed at the end, which was about 1.077. Of course, the volume collected towards the end was a couple ounces-I would say not enough to budge the needle on overall gravity after adding. If one is most interested in hitting volume into the fermentor numbers, squeezing every last bit out is important-especially if you're adding top off water(as I sometimes do-still dialing in my boil off rate). If you're more interested in hitting your target gravity--those last precious ounces of wort aren't really doing much i.e it's not a high gravity syrup that's going to boost your OG much. Does that make sense? Did I forget something and my conclusion is off-base? I'm sure you'll let me know.
Cheers!
Click to expand...
I concur with your conclusion and only squeeze the wort out of the grains to hit the proper volume.
 
Of course the gravity of the squeezed grain isn't going to be higher if you have achieved full conversion. The grain is just acting like a wort sponge at that oint. All you are effectively doing is reducing grain absorption by squeezing.

Squeezing the bag does give a higher overall efficiency because you need less grains for a given volume of a given OG wort. This is fact.
 
And if you poured your top-off water through the grain in the bag, letting it collect in the bucket below?

Second runnings, maybe, but you'll get more gravity in your top-off water than you would using plain water.
 
I'd like to see someone do a comparison between squeezing the bag and just letting the bag free drain for 20-30 minutes, to see how much wort is retained by each. Reason is that some are turned off to BIAB, citing that they don't like handling the hot, sticky, messy bag.

I have always felt that if you are making a mess and or burning your hands, you're doing something wrong.

I have felt for a while that the easiest approach is to patiently do nothing and let the grain bag free drain by gravity, and the frequent implication that you need to "squeeze the bag" like it owes you money can be a deterrent to a noob BIAB'er.
 
Guys that do 3 gallon or less batches should not be buring their hands squeezing the bag. I suspend my bag in a collendar and w/a coffee cup in each hand I PRESS not SQUEEZE as much out as I can. I can usually get close to 1/3 of a gallon out of 6 lbs of grain. And this wort has the same SG as that that was in the cooler when the bag was removed.
 
wilserbrewer said:
I'd like to see someone do a comparison between squeezing the bag and just letting the bag free drain for 20-30 minutes, to see how much wort is retained by each. Reason is that some are turned off to BIAB, citing that they don't like handling the hot, sticky, messy bag.

I have always felt that if you are making a mess and or burning your hands, you're doing something wrong.

I have felt for a while that the easiest approach is to patiently do nothing and let the grain bag free drain by gravity, and the frequent implication that you need to "squeeze the bag" like it owes you money can be a deterrent to a noob BIAB'er.
Click to expand...

I'd try that except at 30 minutes, my wort has already been boiling for 20. I just don't have the patience to wait that long for the bag to drip out. :cross:
 
I would likely feel the same if I were stove topping smaller batches, I guess I should have been clearer. Looking for someone doing larger, 5-10 gallon batches, either using a pulley or dropping the bag in another container to drain.
 
I mash my 10-13 pounds of grain for 60 minutes at 150' then I hang my bag until the juice runs out. I don't heat it to 170'. I get around 72-75 efficiency.

5 gallon batches
 
After my fourth biab I was pleased to hit fermentor volume and gravity spot on today. I squeezed the bag a few times using cutting boards and let the bag drain until I reached a boil.

The grains were ran through the mill 3 times. I was pleased with the results and not having to go crazy with burning myself squeezing the bag.

As someone said I think it's all about grain/hop absorption.
 
+1 to pour over or bucket sparge instead. It will get you more gravity into the kettle than no sparge + top off with plain water.

I raise the bag and let it drain as long as necessary for it to slow way down. Then I put the bag in a bucket or old cooler and sparge it, then let it drain again.

I'm not a bag squeezer! :D
 
I figure if I'm topping off anyway the water might as well get a chance to meet the grains first. Makes trhem all friendly and homsey like :)
 
Magnus314 said:
+1 to pour over or bucket sparge instead. It will get you more gravity into the kettle than no sparge + top off with plain water.

I raise the bag and let it drain as long as necessary for it to slow way down. Then I put the bag in a bucket or old cooler and sparge it, then let it drain again.

I'm not a bag squeezer! :D
Click to expand...

I hit 81% brew house on a 10 gallon Berliner weiss. Gravity was 1.042 10 gallons after 10 minute boil. 11 gallons of water, 13 lbs grain, single crush at the brew shop. I only pressed on the bag to be a little over 10 gallons pre boil.
 
Although I am a manly man and I LOVE to SCOOB (Squeze The Crap Out Of the Bag) :ban: I have to admit that in larger BIAB brews (20+ pound grain bill) it's inefficient. I did the girlie man thing and used a winch to pull out the bag, and didnt squeeze, just let it drip into a pot. (well I did a little squeezing out of OCD). It was SO MUCH more relaxing to not squeeze. :mug:
I still did a dunk sparge, but the drip method gives good results.
The squeeze is going to net you what ... 4 more ounces, compared to the drip method?

I think the key is let the bag drip for a while, do a dunk sparge, then let drip again.
 
I hit 80% today with some nice squeezes. Only did a double crush instead of a triple crush too. I ended with just a little bit more water for the boil...maybe a quart. Maybe that gave me the extra efficiency.
 
ArcLight said:
Although I am a manly man and I LOVE to SCOOB (Squeze The Crap Out Of the Bag) :ban: I have to admit that in larger BIAB brews (20+ pound grain bill) it's inefficient. I did the girlie man thing and used a winch to pull out the bag, and didnt squeeze, just let it drip into a pot. (well I did a little squeezing out of OCD). It was SO MUCH more relaxing to not squeeze. :mug:
I still did a dunk sparge, but the drip method gives good results.
The squeeze is going to net you what ... 4 more ounces, compared to the drip method?

I think the key is let the bag drip for a while, do a dunk sparge, then let drip again.
Click to expand...


Ok your going the right direction giving up the squeeze. Next step in the rehab is to give up the dunk sparge. It's a hassle IMO. If you want or need to sparge, just gently pour sparge water gently over and through the bag as it is hanging over the kettle....effortless bliss :)
 
wilserbrewer said:
Ok your going the right direction giving up the squeeze. Next step in the rehab is to give up the dunk sparge. It's a hassle IMO. If you want or need to sparge, just gently pour sparge water gently over and through the bag as it is hanging over the kettle....effortless bliss :)
Click to expand...

I still think the dunk sparge adds a noticeable additional amount of fermentables.
In fairness, we need to conduct a test, two side by side brews: one with a dunk sparge, the other with the "pour some water through the bag.

Using the dunk sparge - I get at least 10% more fermentable than not dunking, and a lot more for 20+ pound grain bills, that tend to have more trapped liquid.

If the pour method is almost as efficient, i can see using it instead.
Though I wonder how it compares to not pouring and mashing with all your water in one pot.

I suppose the next time I brew I could try pouring water through the bag and trap the runnings in a second pot and measure it's gravity.


I don't need rehab, I need to squeeze some wet grain ... :tank:
 
How about a dunk sparse vs full volume? Dunk sparse or rinse through accomplishes the same thing. You rinse the grains
 
that's a great system... I think someone needs to let the bag drip as suggested, then squeeze it into another bucket just to see the amount of good wort left in the bag...with my 10-12# grainbills I get over 1/2 gallon of 'free' wort.
 
I used to hang with a block and tackle, but now that I've moved to brewing outside during nice weather, I have just been lifting the back, letting it rest on my paddle while it drains a bit more. Then when it gets lighter, I grab the top of my bag that isn't hot or sticky, and spin the bag so the bag actually squeezed the grain. Rest on paddle. Repeat until you get your desired volume.

It doesn't take more than 5 minutes for it to be almost completely done dripping by then. I'm doing 10 gallon batches by the way.
 
OmegaRed said:
I used to hang with a block and tackle, but now that I've moved to brewing outside during nice weather, I have just been lifting the back, letting it rest on my paddle while it drains a bit more. Then when it gets lighter, I grab the top of my bag that isn't hot or sticky, and spin the bag so the bag actually squeezed the grain. Rest on paddle. Repeat until you get your desired volume.

It doesn't take more than 5 minutes for it to be almost completely done dripping by then. I'm doing 10 gallon batches by the way.
Click to expand...

You are a MANLY man if you can lift 20+ pounds of wet grain with one hand and support it for 5 minutes. :fro:

While I too am a MANLY man and can lift 25 pounds of wet grain, I decided it was easier to use a $6 ratchet hung from a ladder. I'm still a MANLY man, but I watch gravity drain the bag, which I think is easier and more effective than having the bag rest on a paddle or sit in a colander. The bag kind of flops around with a mash paddle doesn't it? Do you put the paddle across teh pot, and use both hands to support the bag?

Because I'm OCD I still do a dunk sparge, despite wilserbrewers best efforts to cure me :ban:
 
william_shakes_beer said:
I do the perforated bucket method and have virtuallty no absorption loss (less than a quart on a 15 pound grain bill)
Click to expand...


Can you explain in more detail?

1. You put the bag in a bucket with holes drilled.
(How many holes and what diameter?)

2. How do you press down on the bag, with another bucket?
(How much pressure do you apply, and how, so as to have almost no liquid loss ?)

3. How do you collect the runnings? Do you have a third bucket, or spare pot?
 
BowAholic said:
that's a great system... I think someone needs to let the bag drip as suggested, then squeeze it into another bucket just to see the amount of good wort left in the bag...with my 10-12# grainbills I get over 1/2 gallon of 'free' wort.
Click to expand...

After it's drained by gravity, squeezing wont get you much more.
If you want more sugar out of the grain, you can do a dunk sparge, or a "pour sparge"*.

* "Pour sparge" = pour some water into the top of the bag, (possibly while supporting the bag with one hand for better absorbsion) so the water doesn't run down the side. Do this a couple of times.
 
ArcLight said:
Can you explain in more detail?

1. You put the bag in a bucket with holes drilled.
(How many holes and what diameter?)

2. How do you press down on the bag, with another bucket?
(How much pressure do you apply, and how, so as to have almost no liquid loss ?)

3. How do you collect the runnings? Do you have a third bucket, or spare pot?
Click to expand...

bucket 1: 5 gallon "homer bucket" with holed drilled in bottom and sides. Half inch holes spaced about 2 inches apart. Be sure to stop the holes short of the handle gusset so the handle will still retain structural integrity

bucket 2: 7.5 gallon "ale pail" fermenter


1. Place bucket 1 inside bucket 2 (if they both accept the same lid they will nest)

2. Pull bag, hold over kettle to drip until my arms give out.

3. Place bag in bucket 1

4. let gravity do the work. No pressing required. when the boil reaches about 185 I check bucket 2 and pour its contents into the kettle.

If you have 2 fermenters available you can swap bucket 1 back and forth but its not really necessary. The space between the 5 gallon bucket and the 7.5 gallon bucket provides a free space for the wort to collect below the bag.

Was that helpful?
 
In theory, pouring water over the mass of grain is going to generally find a few pathways to get through and avoid a lot of others. It's the definition of channeling that people talk about with fly sparging. With 16 pounds of grain, I was able to squeeze out almost a half gallon more than what would drip out naturally and believe me I let it hang there for 15 minutes without a drop.
 
william_shakes_beer said:
bucket 1: 5 gallon "homer bucket" with holed drilled in bottom and sides. Half inch holes spaced about 2 inches apart. Be sure to stop the holes short of the handle gusset so the handle will still retain structural integrity

bucket 2: 7.5 gallon "ale pail" fermenter

... snip ...

4. let gravity do the work. No pressing required. when the boil reaches about 185
Click to expand...

No pressing required?!?!?! :confused: :(

Aw ...

I was looking forward to some kind of manly pressing down on the drilled bucket, with a third bucket, trying to crush the grain to a black hole.

And I so wanted to hear about standing on the bucket to press the grain bag ... :fro:


Personally, I just let gravity do it's think while the bag is hanging from a ratchet.
 
Bobby_M said:
In theory, pouring water over the mass of grain is going to generally find a few pathways to get through and avoid a lot of others. It's the definition of channeling that people talk about with fly sparging. With 16 pounds of grain, I was able to squeeze out almost a half gallon more than what would drip out naturally and believe me I let it hang there for 15 minutes without a drop.
Click to expand...

Bobby, I used to do that, but I find a dunk sparge does even better. Let it drain for 5 minutes, then dunk into a second pot, stir, and pull and gravity drain the bag.
I get a lot of sugar out of the dunk sparge.
 
Like I said in a previous post, I usually get an extra quart or two by pressing after letting it drain for awhile. Likely would have gotten some more out if it were hanging instead of sitting in a bucket, but a 15 second press does the work much quicker. I use a pot lid.
 
Hi all, I've been a long time reader and have meant to join in the discussions for a long while now, but life put brewing well into the background over the last few years. So, by way of introduction, I'm a long time home brewer, some time (almost 3 years) craft brewer, now back to brewing only at home. Discussions here, melded with what I picked up working as a brewer have helped me put together a solid BIAB system with keeper and fermenting/conditioning fridge that can operate reliably and repeatably up to the 104 deg F + we get here.

I've been through the different ways of dealing with the bag. At first, no dunk sparge and a bit of squeezing-this made great beer. Then, after putting numbers in software, I was unhappy with the efficiency and moved to sparking with 6L of water. Here's where the problems began. Suddenly, I started getting brews with some harshness or off flavours. These were getting in the way of the hop and malt flavours. They varied in intensity and were less noticeable in stouts, but could (in my picky opinion) ruin a lighter beer, especially the low alcohol ones. I also noticed some improvement after conditioning/clearing.

Anyway, turns out I was creating problems by either over-sparging or getting the pH of the sparge wrong and extracting tannins as I have high pH ground water. I stopped sparging and went back to the squeeze. In a normal gravity beer it cost 4-5% efficiency, but I ended up with beer that was back on point from wort to glass. So BEWARE the badly executed sparge!
Cheers
Rob
 
Roboutwest said:
Hi all, I've been a long time reader and have meant to join in the discussions for a long while now, but life put brewing well into the background over the last few years. So, by way of introduction, I'm a long time home brewer, some time (almost 3 years) craft brewer, now back to brewing only at home. Discussions here, melded with what I picked up working as a brewer have helped me put together a solid BIAB system with keeper and fermenting/conditioning fridge that can operate reliably and repeatably up to the 104 deg F + we get here.

I've been through the different ways of dealing with the bag. At first, no dunk sparge and a bit of squeezing-this made great beer. Then, after putting numbers in software, I was unhappy with the efficiency and moved to sparking with 6L of water. Here's where the problems began. Suddenly, I started getting brews with some harshness or off flavours. These were getting in the way of the hop and malt flavours. They varied in intensity and were less noticeable in stouts, but could (in my picky opinion) ruin a lighter beer, especially the low alcohol ones. I also noticed some improvement after conditioning/clearing.

Anyway, turns out I was creating problems by either over-sparging or getting the pH of the sparge wrong and extracting tannins as I have high pH ground water. I stopped sparging and went back to the squeeze. In a normal gravity beer it cost 4-5% efficiency, but I ended up with beer that was back on point from wort to glass. So BEWARE the badly executed sparge!
Cheers
Rob
Click to expand...

I assume you were sparging with hot water, right? Could this have been avoided if you would have used room temp water instead? I've read that tannin extraction requires both high pH and high temps.
 
Yes, sparging with 75 degree C water as usual. Hot water usually gets more sugar out. High ph sparge water was something I was always told to avoid at the brewery.
 
Concerning the concept that hot water gets more sugar out, you might want to read Kai Troester's write up on cold vs hot sparge. No difference in efficiency was seen in his experiment. Lots of folks on the forum also use, or have used, a cold (room temp) sparge with no ill effects.

http://braukaiser.com/blog/blog/2009/05/12/cold-water-sparging/

Although I wouldn't think 75 C water would cause any tannin issues, it'd be interesting to try something like 65 C sparge water and see if that makes a difference. Might even do a small batch so that you don't waste a bunch of grains if it turns into a dumper.
 
I do a dunk sparge with 20-25C (68 - 77 degrees) water. The sugar is no where near the saturation point so you don't need the extra temperature.
In addition the dunk sparge is performed with the remainder of the water.
Ex: you want 12 gallons of wort. Mash with 7.5 and dunk sparge with 4.5
The total water will be the same as if you did a full volume BIAB.
In addition the dunk sparge doesn't last very long, maybe several minutes.
Then raise the bag again and let drip dry.
Having said that - I suppose it's possible to extract tannins.
I haven't tasted any, but I'm not a BCJP certified judge.
 
ArcLight said:
... The sugar is no where near the saturation point so you don't need the extra temperature...
Click to expand...

This is absolutely true (I've posted the data in other threads on HBT), especially for second runnings. Hot sparge water might have some benefit in a couple of cases.
  1. Your mash conversion was incomplete (not all available starch converted to sugar.) In that case the higher temps can get you a little more conversion, until the high temps denature most of the amylase.
  2. You have a coarse crush, in which case higher temps can speed up diffusion of remaining sugar absorbed in the grain particles out into the wort. However, vigorous stirring during a batch sparge is much more effective at that then waiting for still diffusion to get to equilibrium.
Recommendations:
  1. crush fine (I use a 0.4 mm roller gap, and some BIAB'ers grind to almost flour,)
  2. keep sparge water less than 70°C (so overshoots can't get you into tannin extraction territory, and
  3. stir vigorously for at least 5 minutes before running off your sparged wort.
Do this and it won't matter how cool your sparge water temp.

Brew on :mug:
 
Well I'll be... it makes perfect sense that cold would work when you put it that way Texas (i.e.. the sugar solution is not near saturated). It always amazes me that there is so much myth busting going on in brewing these days. That's why I love reading the Brulosopher. I was completely floored out by the quality I can get with a full volume mash when all the pros in the orthodoxy were knocking it for various reasons. Now I appreciate its simplicity, which is one reason i'm not too upset to go Wilser's way and K.I.S.S.. That said, I might try a cold sparge for high gravity beers where there is a lot of sugar left in the bag.
 
ArcLight said:
You are a MANLY man if you can lift 20+ pounds of wet grain with one hand and support it for 5 minutes. :fro:

While I too am a MANLY man and can lift 25 pounds of wet grain, I decided it was easier to use a $6 ratchet hung from a ladder. I'm still a MANLY man, but I watch gravity drain the bag, which I think is easier and more effective than having the bag rest on a paddle or sit in a colander. The bag kind of flops around with a mash paddle doesn't it? Do you put the paddle across teh pot, and use both hands to support the bag?

Because I'm OCD I still do a dunk sparge, despite wilserbrewers best efforts to cure me :ban:
Click to expand...


That's the thing though, you're not letting gravity drain the bag. You're squeezing the grain with your bag, because you twist the bag, which does a really good job of squeezing (without you having to touch any hot or sticky areas on the bag).

And yes initially I set the paddle across the kettle, and set the bag on it. For lack of a better descriptor, it looks like a nut sack. You decide which one hangs lower. Mine is the left. :mug:
 

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