No oxygen dry hopping

[Robert65]

When filling a keg, my method to ensure no O2 ingress is to put a picnic tap on the gas post and periodically bleed pressure to maintain flow. Like the purge valve on a CP bottling rig. This also ensures that things don't get away from me if I step away.

 

[CodeSection]

I can view my Raspberry Pints tap list literally anywhere with an internet connection - the above was a screen grab from my office workstation - but its primary function is to drive the display atop my keezer tower...


View attachment 669729

Cheers!

Impressive setup!

 

[ttuato]

I will contribute to the thread - I used some of the knowledge here and crafted my own version/process for lodo dryhopping spike flex+.

Since I hop heavy I wanted the chamber large enough to hold at least 16ozs of pellets at once - roughly the equivalent of a quart mason jar. I tested reducers to spools to the 1.5" opening on top of flex. Not only did it require long reducers/spools but the 1.5" butterfly did not dump the hops very easily. So I shifted to the 4" cap and used 4" to 3" concentric reducer and 3" butterfly valve. This valve dumped effortlessly and only needed about 10" spool. This allowed me to use the 3" hop filter from brewhardware.com That I already owned. I removed the inner hard filter so that it just a "tube" - one end is 3", the other is 1.5". I added a 1.5" cap with ball lock gas connect and attached a hose to the bottom that is the length of the tube (more later on later)

• I purged a keg using fermentation gas for a couple of days, I removed the blowoff and harvested some gas into the keg while spunding the beer to 15psi. The PRV in the flex limited the pressure that could build in the attached keg as well, which avoided any risk of over pressurizing the dryhopper later in the process.
• When time to dryhop, I pulled the spike from from the fridge
• With the gas line inside the tube I filled the hops (tube will hold ~18-20oz). I used the ferm gas from keg to purge gas cap first so it will push O2 out of gas line. Then I used my nitro purge wand to purge from bottom which pushed up through the hops. Then I held the cap down and slowly opened the butterfly valve so that the spunded gas would purge again from the bottom up through the hops - repeated this twice. I then sealed and used the last of the keg ferm gas to pressurize the dryhopper, then opened the butterfly fully to dump hops and closed back.
  
• Entire process took about five minutes
• 
  
  
  
  
  
  
  
  
• 

 

[mcl]

Here is a pic of my setup using the Brewers Hardware conical. I used the reducer as I had a 3" port available and it also shouldn't clump and jam. Also I have to ability to put one of my PRV valves on top if I want. I don't have it configured that way at the moment.

 

[bracconiere]

who knows what actually happens to it all

https://www.npr.org/sections/goatsa...lastic-trash-go-now-that-china-doesnt-want-it

 

[jturman35]

I will contribute to the thread - I used some of the knowledge here and crafted my own version/process for lodo dryhopping spike flex+.

Since I hop heavy I wanted the chamber large enough to hold at least 16ozs of pellets at once - roughly the equivalent of a quart mason jar. I tested reducers to spools to the 1.5" opening on top of flex. Not only did it require long reducers/spools but the 1.5" butterfly did not dump the hops very easily. So I shifted to the 4" cap and used 4" to 3" concentric reducer and 3" butterfly valve. This valve dumped effortlessly and only needed about 10" spool. This allowed me to use the 3" hop filter from brewhardware.com That I already owned. I removed the inner hard filter so that it just a "tube" - one end is 3", the other is 1.5". I added a 1.5" cap with ball lock gas connect and attached a hose to the bottom that is the length of the tube (more later on later)

• I purged a keg using fermentation gas for a couple of days, I removed the blowoff and harvested some gas into the keg while spunding the beer to 15psi. The PRV in the flex limited the pressure that could build in the attached keg as well, which avoided any risk of over pressurizing the dryhopper later in the process.
• When time to dryhop, I pulled the spike from from the fridge
• With the gas line inside the tube I filled the hops (tube will hold ~18-20oz). I used the ferm gas from keg to purge gas cap first so it will push O2 out of gas line. Then I used my nitro purge wand to purge from bottom which pushed up through the hops. Then I held the cap down and slowly opened the butterfly valve so that the spunded gas would purge again from the bottom up through the hops - repeated this twice. I then sealed and used the last of the keg ferm gas to pressurize the dryhopper, then opened the butterfly fully to dump hops and closed back.
  
• Entire process took about five minutes
• 
  
  
  
  
  
  
  
  
• 

Wish the pictures were viewable.

 

[ShaLaH]

OK, time to report! Finally had a chance to try out the butterfly valve/sight glass/pressure manifold thing to introduce dry hopping hops, and I'm pleased to report that....it worked!

Here's a short video showing how it went down:

I tried dry hopping using this technique today. Here's what happened:

I put the butterfly valve on the 1.5" port, then the sight glass filled with hops on that, then the spike manifold on top of that (just how you have it). I cracked the butterfly valve open slightly, then hooked up CO2 to the manifold and added a 3-4 psi. Waited a couple minutes for sight glass to fill with CO2. Then, I opened the valve, working it back and forth but the hops wouldn't drop. I had to take everything apart and just dump the damn hops in. Somehow the hops got pushed up into the manifold and were compacted. What did I do wrong?

I'm assuming I didn't release the pressure before dropping the hops right?

 

[kevink]

I tried dry hopping using this technique today. Here's what happened:

I put the butterfly valve on the 1.5" port, then the sight glass filled with hops on that, then the spike manifold on top of that (just how you have it). I cracked the butterfly valve open slightly, then hooked up CO2 to the manifold and added a 3-4 psi. Waited a couple minutes for sight glass to fill with CO2. Then, I opened the valve, working it back and forth but the hops wouldn't drop. I had to take everything apart and just dump the damn hops in. Somehow the hops got pushed up into the manifold and were compacted. What did I do wrong?

I'm assuming I didn't release the pressure before dropping the hops right?

I use a 2" valve and they dump right in. Did you try tapping on the valve with a rubber mallet or something like that?

 

[ShaLaH]

I use a 2" valve and they dump right in. Did you try tapping on the valve with a rubber mallet or something like that?

yup, definitely banged on it. I have the spike cf5, so I only have access to a 1.5" port on the lid.

 

[kevink]

yup, definitely banged on it. I have the spike cf5, so I only have access to a 1.5" port on the lid.

Damn. Did you make sure that there were no two pellets stuck together? That can cause problems. They all have to be completely un-stuck from each other.

 

[ShaLaH]

Damn. Did you make sure that there were no two pellets stuck together? That can cause problems. They all have to be completely un-stuck from each other.

I didn't. I think next time I'll grind the hops up and then add to the sight glass.

 

[mongoose33]

Here's what I know about how this works.

First, you need to not overfill with hops. Otherwise, when you open the valve you're going to compress some of those hops upward, which will create bridging.

That's the fundamental issue--bridging. A 2" valve would be better, as @kevink has above but if you have the 1.5" valve (which you do), you have to be careful with that.

I had CO2 hooked up to mine with the idea that I might need to blast them down into the fermenter. That's never worked particularly well but I thought a shot of CO2 at, say, 20 or 25 psi might do it.

I also found this: When I did this in my garage in the winter, where the garage was 40-50 degrees ambient, and I had beer fermenting at, say, 65 degrees, I'd get condensation on the inside of the sight glass. This made the hops sticky to some extent. So that has to be addressed too. During warmer periods in the garage it isn't an issue.

I'm guessing you maybe had too many hops jammed in there.

*****

The idea behind this in part was to add the hops a day or so ahead of dropping them so that the CO2 being produced by the yeast would purge the hops in the sight glass, allowing the excess to flow out the manifold. That would purge them completely, then I'd drop them.

Just pouring in the hops, adding some CO2, and dropping them doesn't purge of oxygen.

 

[ShaLaH]

Here's what I know about how this works.

First, you need to not overfill with hops. Otherwise, when you open the valve you're going to compress some of those hops upward, which will create bridging.

That's the fundamental issue--bridging. A 2" valve would be better, as @kevink has above but if you have the 1.5" valve (which you do), you have to be careful with that.

I had CO2 hooked up to mine with the idea that I might need to blast them down into the fermenter. That's never worked particularly well but I thought a shot of CO2 at, say, 20 or 25 psi might do it.

I also found this: When I did this in my garage in the winter, where the garage was 40-50 degrees ambient, and I had beer fermenting at, say, 65 degrees, I'd get condensation on the inside of the sight glass. This made the hops sticky to some extent. So that has to be addressed too. During warmer periods in the garage it isn't an issue.

I'm guessing you maybe had too many hops jammed in there.

*****

The idea behind this in part was to add the hops a day or so ahead of dropping them so that the CO2 being produced by the yeast would purge the hops in the sight glass, allowing the excess to flow out the manifold. That would purge them completely, then I'd drop them.

Just pouring in the hops, adding some CO2, and dropping them doesn't purge of oxygen.

Thank you sir. That is exactly what happened, I crammed the 1.5" sight glass full of hops and they did indeed compress up into the manifold.
I also missed the part where you let the hops sit for a day prior to dropping them. Knowledge for next time, thanks for the info.

 

[ttuato]

@jturman35 @mkblackmart @murphyslaw @duelerx

here are the images. Again smaller sized so hopefully will come through. My Process/setup is similar to @mcl posted after me. Here is what I have learned / changed after 9 batches - tgis only works if you spund.

• Dont need the balllock pressure thing at top, just use a flat TC plate to cap the top
• Use wand to purge device from bottom after mounting dryhop tube
• Add hops, insert wand again and purge hops, quickly put on TC cap.
• Add TC clamp to cap but do not tighten yet
• Barely & slowly crack the dump valve just enough so that the PURE CO2 from FV will enter the DH chamber from bottom for a, resulting in a third purge.
• While the pure CO2 is exiting the dryhopper, tighte the TC clamp at the top, sealing the dryhopper. Wait a few seconds for the pressure to normalize, then dump
• RESULTS - I have seen a definite improvement in the shelf life using this method, aroma stays tight, nocardboard flavors, no color change, etc.
• BUT - big BUT - I have noticed that floculation is playing a bigger role in the later part. Normally I finish my hazies in 6-8 or less. I purposefully left one in the keezer for 12 weeks with about 2gal. No signa of oxidation still but the flavor & mouthfeel had declined (I use floating diptubes). As it got closer to the bottom where all of the goodness had flocced out, thw flavor moutfeel came back...
• 
  
  
  
  

 

[Vale71]

The idea behind this in part was to add the hops a day or so ahead of dropping them so that the CO2 being produced by the yeast would purge the hops in the sight glass, allowing the excess to flow out the manifold. That would purge them completely, then I'd drop them.

Just pouring in the hops, adding some CO2, and dropping them doesn't purge of oxygen.

Your technique doesn't purge the chamber completely either. The reason being, oxygen is a gas and it will diffuse in all directions, including into the FV's headspace, and not just flow out of the manifold. The result will be that you will have to wait for fermentation to purge all the residual oxygen from the headspace and the dry hopping chamber s well and this will most likely take longer than one day. If one want to be sure that residual oxygen levels are negligible one ought to actively purge the chamber before opening the valve, which would also allow dry hopping at a later time when active fermentation is done.

 

[mongoose33]

Your technique doesn't purge the chamber completely either. The reason being, oxygen is a gas and it will diffuse in all directions, including into the FV's headspace, and not just flow out of the manifold. The result will be that you will have to wait for fermentation to purge all the residual oxygen from the headspace and the dry hopping chamber s well and this will most likely take longer than one day. If one want to be sure that residual oxygen levels are negligible one ought to actively purge the chamber before opening the valve, which would also allow dry hopping at a later time when active fermentation is done.

I don't do it the first day. I wait until the 3rd day, generally, before any of his happens. Meanwhile the oxygen in the headspace is either being consumed by the yeast, or being expelled by the CO2 released. Given the volume of CO2 being produced, by the third day the headspace should be clear of O2, and then I begin the process of hops in the sight glass. I'll close the butterfly valve and let the fermenter build up a bit of CO2 pressure, add the hops, top off with the manifold, and then crack the valve a bit to allow CO2 to escape through the hops.

Is it producing a perfectly oxygen-free environment? I think it's pretty good, darned good in fact, but perfect? Nah.

But it's one heck of a lot better than the old way of doing it, i.e., open up the fermenter, dump in the hops, allow a lot of air and O2 to mix in, and close back up.

********​

During fermentation about 1 volume of CO2 is produced for every 2 points of gravity drop (this from the low-oxy stuff). It takes about 25 purges of a vessel with pure CO2 to get down to a virtually O2-free environment. So if it dropped in gravity from, say, 1.060 to 1.010, that's 50 points; divided by 2 is 25 volumes. So a 5-gallon batch produces about 125 gallons of CO2.

Roughly. Lower starting gravity, or higher finishing gravity reduces that somewhat.

So when that expelled CO2 goes through the much smaller volume of the sight glass and associated connections, it's purging that space pretty quickly. I haven't done the math, but even one volume of CO2 produced (5 gallons) is....well, time out while I do a little math:

Assume a 12-inch cylinder of sight glass etc. times 1.5" of diameter....lessee....pi-r-squared is the area of the circle....3.14 x .75 x .75 is ...about 1.77 square inches. Times 12" of height is 21.24 cubic inches of volume in the sight glass and associated stuff. (overestimating by a bit, but that's ok, it's the right side on which to make that error, more conservative).

There are 231 cubic inches in one gallon; in five gallons there are 1155 cubic inches. Divide that by the 21.24 cubic inches of the sight glass, and 1-volume of CO2 from fermentation will be equivalent to....1255 / 21.24 = 59.xx. Or 59 purges. You can check the math, but I think it's right.

So if one doesn't allow air to go into the top of the fermenter while doing this, one should be able to purge the sight glass, and the hops inside, in just the few hours it takes for fermentation to drop gravity by about 2 points.

That's why I do it late--to purge the headspace of the fermenter and then allow enough remaining fermentation to purge the sight glass and hops.

******​

Perfect? No. I'm sure there's O2 inside hop pellets, though not much. Probably can't get rid of that in purging, but its volume compared even to the sight glass is miniscule. But when I dump in the hop pellets and they melt in the beer, that O2 should be consumed by the yeast.

********​

It's better to use the CO2 produced by fermentation, if possible, because it's pure. CO2 from a tank, unless one paid for a very high level of purity, is about 99.5 percent CO2; the rest air. In that air is 21 percent oxygen. So 21 percent of the remaining .5 percent is about .1 percent, so in one's CO2 is about .1 percent oxygen. Just trying to eliminate all the O2 I can.

 

[Vale71]

It's better to use the CO2 produced by fermentation, if possible, because it's pure. CO2 from a tank, unless one paid for a very high level of purity, is about 99.5 percent CO2; the rest air. In that air is 21 percent oxygen. So 21 percent of the remaining .5 percent is about .1 percent, so in one's CO2 is about .1 percent oxygen. Just trying to eliminate all the O2 I can.

That is wrong and I've already pointed it out to you several times. Just download the specs for food grade CO2 from the major suppliers and you'll see that they guarantee at most 50ppm of residual O2, at best as little as 20ppm. That's a far cry from 0.5% or 5000ppm. If 50 ppm is still too much for you could purge the hopper with a high vacuum pump and skip the last pressurization step. If you drop residual pressure down to a few millibar and then crack open the valve letting headspace gas fill the cylinder you'd hardly have introduced any residual O2 from your bottled CO2.

As for keeping the O2 out of the headspace with your method the problem is that fermentation only creates a very slow flow of CO2, way too slow to mechanically purge the cylinder. Gas diffusion is much faster than that and this means that nearly all the O2 that you have in the cylinder will uniformly diffuse into the headspace within an hour or less. At that point fermentation CO2 will have to progressively scrub the O2 from the headspace and depending on how far fermentation has already progressed this could very likely result in residual O2 levels that are significantly higher than what they would have been had no O2 been introduced after fermentation began. Granted this will still be better than opening up the fermenter but still much worse than using bottled CO2 with at worst 50ppm residual O2 since with your method you'll be introducing exactly the same volume of gas to the fermenter but with about 210,000ppm of O2 or 4,200 times more.

 

[mongoose33]

That is wrong and I've already pointed it out to you several times. Just download the specs for food grade CO2 from the major suppliers and you'll see that they guarantee at most 50ppm of residual O2, at best as little as 20ppm. That's a far cry from 0.5% or 5000ppm. If 50 ppm is still too much for you could purge the hopper with a high vacuum pump and skip the last pressurization step. If you drop residual pressure down to a few millibar and then crack open the valve letting headspace gas fill the cylinder you'd hardly have introduced any residual O2 from your bottled CO2.

As for keeping the O2 out of the headspace with your method the problem is that fermentation only creates a very slow flow of CO2, way too slow to mechanically purge the cylinder. Gas diffusion is much faster than that and this means that nearly all the O2 that you have in the cylinder will uniformly diffuse into the headspace within an hour or less. At that point fermentation CO2 will have to progressively scrub the O2 from the headspace and depending on how far fermentation has already progressed this could very likely result in residual O2 levels that are significantly higher than what they would have been had no O2 been introduced after fermentation began. Granted this will still be better than opening up the fermenter but still much worse than using bottled CO2 with at worst 50ppm residual O2 since with your method you'll be introducing exactly the same volume of gas to the fermenter but with about 210,000ppm of O2 or 4,200 times more.

We're going to have to disagree here. I asked my supplier of CO2 about this and the numbers I quoted are what he told me. So maybe there are places where you can get super-pure CO2. My local supplier isn't one of them.

As for the rest, again, we'll have to disagree. I don't think my numbers are incorrect. The math is right, I believe, and the logic as well.

And I surely cannot see how you think I'm introducing more than a miniscule amount (if that) of oxygen into my system. Perhaps a reread of what I do might be in order.

 

[Vale71]

We're going to have to disagree here. I asked my supplier of CO2 about this and the numbers I quoted are what he told me. So maybe there are places where you can get super-pure CO2. My local supplier isn't one of them.

As for the rest, again, we'll have to disagree. I don't think my numbers are incorrect. The math is right, I believe, and the logic as well.

And I surely cannot see how you think I'm introducing more than a miniscule amount (if that) of oxygen into my system. Perhaps a reread of what I do might be in order.

So you don't think that O2 will diffuse quickly into the headspace but believe that it will stay in place and be pushed out by fermentation CO2? I'm sorry but that idea is completely wrong. As it's not a matter of opinion there is nothing on which to agree or disagree. Behaviour of gases has been known rather well for over 200 years, there is no need to reinvent anything. Your math may be right but your understanding of the underlying physics is simply wrong leading to incorrect results.

As for your supplier claiming 0,5% air in the gas he either doesn't know what he's talking about or he's purposefully contaminating his stock to reach such high levels. I would ask him for a spec sheet or at least the name of his supplier so that you can ask them directly. In any case I don't see according to which logic one could consider using air with 210,000ppm oxygen les crititical than using bottled CO2, even assuming the latter could have 10,000ppm oxygen as you incorrectly claim. After all 210,000 is stil 21 times more than 10,000 or is my math incorrect?

 

[Rainy]

So you don't think that O2 will diffuse quickly into the headspace but believe that it will stay in place and be pushed out by fermentation CO2? I'm sorry but that idea is completely wrong. As it's not a matter of opinion there is nothing on which to agree or disagree. Behaviour of gases has been known rather well for over 200 years, there is no need to reinvent anything. Your math may be right but your understanding of the underlying physics is simply wrong leading to incorrect results.

As for your supplier claiming 0,5% air in the gas he either doesn't know what he's talking about or he's purposefully contaminating his stock to reach such high levels. I would ask him for a spec sheet or at least the name of his supplier so that you can ask them directly. In any case I don't see according to which logic one could consider using air with 210,000ppm oxygen les crititical than using bottled CO2, even assuming the latter could have 10,000ppm oxygen as you incorrectly claim. After all 210,000 is stil 21 times more than 10,000 or is my math incorrect?

And what about letting pressure (15psi) build up in the fermenter with the butterfly valve closed, loading the dry hop cylinder with hops, putting a spunding (set at 10psi) valve on the top of the dry hop cylinder, and then slowly opening the butterfly valve to have a slow steady flow of CO2 from the fermenter go through the dry hop cylinder. Most likely there will be too much mixing of the CO2 with the air in the cylinder, but if the flow of CO2 can be controlled to be slow (by adjusting the spunding valve pressure closer to the pressure in the fermenter) mixing could be reduced. This would then flush the dry hop cylinder of CO2 within a matter of a minute, hence diffusion not coming into play.

 

[Vale71]

You'd have either to ferment under pressure or dry hop after spunding. In each case you'll lose CO2 and hence pressure. In the latter case you'll have to add CO2 from a bottle and that's a big no-no if you're conviced bottled CO2 is evil...

A better compromise would actually be to add the dry-hop charge, close off the chamber and then immediately and quickly open and close the valve as soon as the pellets have dropped into the fermenter. This way the O2 in the chamber won't have time to completely diffuse into the headspace but only a portion of it will make it into the fermenter and will then have to be scrubbed by further fermentation.

Paradoxically, with the "fermentation CO2 scrubbing" gimming you're introducing maximum oxygen in the fermenter. By performing a "drop, duck and close" you can only introduce less oxygen as the chamber volume is the same but only a fraction of the oxygen will make it into the fermenter.

 

[mongoose33]

So you don't think that O2 will diffuse quickly into the headspace but believe that it will stay in place and be pushed out by fermentation CO2? I'm sorry but that idea is completely wrong. As it's not a matter of opinion there is nothing on which to agree or disagree. Behaviour of gases has been known rather well for over 200 years, there is no need to reinvent anything. Your math may be right but your understanding of the underlying physics is simply wrong leading to incorrect results.

As for your supplier claiming 0,5% air in the gas he either doesn't know what he's talking about or he's purposefully contaminating his stock to reach such high levels. I would ask him for a spec sheet or at least the name of his supplier so that you can ask them directly. In any case I don't see according to which logic one could consider using air with 210,000ppm oxygen les crititical than using bottled CO2, even assuming the latter could have 10,000ppm oxygen as you incorrectly claim. After all 210,000 is stil 21 times more than 10,000 or is my math incorrect?

We're still going to have to disagree. Can't for the life of me understand what you think you're arguing, but I don't think the O2 will just gather at the exit and be pushed out. This is why the number of purges is important. The number of purges.

Maybe you missed the math above about that. If you take a volume of air which is 21 percent oxygen, and push out gases from that volume with an equal amount of CO2, you can expect that the amount of oxygen remaining is about half of what was there before. Then do it again, and now you have about 1/4 of the oxygen remaining. And again. And again. And again.

Do that 59 times (which is what my math above shows), and you will have reduced the amount of O2 to very, very close to....zero. And thus the gaseous environment surrounding the to-be-dropped hops in the sight glass is essentially....zero.

That's what happens in the sight glass when it's purged 59 times. Now, I'm not sure if you're arguing something different here, but purging is all I'm talking about. Wish I could find that post from @doug293cz that shows how this happens. If I find it, I'll edit and append it.

********

EDITED TO ADD: Keg purging with active fermentation

Doug has posted on this several times, this is just one representative example. His conclusion about purging a keg with fermentation gases? 5 parts per billion. And that's with only the equivalent of 23 purges (23x the volume of CO2). I calculated above that I'd have 59.

********

I'm sorry you don't like what my supplier told me.

 

[eric19312]

Problem with almost all this Low Oxygen stuff is basing decisions off calculations without anybody ever verifying results using a DO meter sensitive in the PPB range. I like Doug's calculations and those on the low oxygen blog but would like to see them verified. Same with the notion regarding amount of O2 in beverage grade CO2.

One comment on Mongoose's technique is it doesn't sound like it is repeatable. You get one shot right? Then there is no more fermentation gas left to purge the next slug of hops. Is this enough hops for you? I am working from the bottom with a Norcal yeast brink and struggling to get 4oz at a time into the fermentor and if the issue of O2 in the tank of CO2 is real I am probably doing more harm than good since it is tanking me something like 10-20 blasts of CO2 to push the hops into the fermenter. I brewed a recipe from Other Half recently that called for 2 pounds of dry hops in 15 gallons. 4oz at a time lol not practical.

I'll keep trying but I was previously getting really good results with minimal effort just bubbling CO2 from the bottom while opening the 4" port on the top and dumping the hops in. I could dump in a pound no problem and then purge the headspace multiple times either continuing to bubble in from the bottom or adding gas in through the pressure manifold. My really good results were obviously not measured with a DO meter but based on getting sufficient for me shelf life of very light colored hazy IPAs. No darkening and decent hop character from beers even out to about 3 weeks from kegging. My IPAs don't usually last much longer than that so maybe chasing a problem that is really not my problem.

 

[ShaLaH]

Problem with almost all this Low Oxygen stuff is basing decisions off calculations without anybody ever verifying results using a DO meter sensitive in the PPB range. I like Doug's calculations and those on the low oxygen blog but would like to see them verified. Same with the notion regarding amount of O2 in beverage grade CO2.

One comment on Mongoose's technique is it doesn't sound like it is repeatable. You get one shot right? Then there is no more fermentation gas left to purge the next slug of hops. Is this enough hops for you? I am working from the bottom with a Norcal yeast brink and struggling to get 4oz at a time into the fermentor and if the issue of O2 in the tank of CO2 is real I am probably doing more harm than good since it is tanking me something like 10-20 blasts of CO2 to push the hops into the fermenter. I brewed a recipe from Other Half recently that called for 2 pounds of dry hops in 15 gallons. 4oz at a time lol not practical.

I'll keep trying but I was previously getting really good results with minimal effort just bubbling CO2 from the bottom while opening the 4" port on the top and dumping the hops in. I could dump in a pound no problem and then purge the headspace multiple times either continuing to bubble in from the bottom or adding gas in through the pressure manifold. My really good results were obviously not measured with a DO meter but based on getting sufficient for me shelf life of very light colored hazy IPAs. No darkening and decent hop character from beers even out to about 3 weeks from kegging. My IPAs don't usually last much longer than that so maybe chasing a problem that is really not my problem.

Yeah, I agree. I'm going back to what is easy and convenient for me. Since I have a dual regulator I'm gonna hook one CO2 line up to the carb stone and the other to the pressure manifold and run them both while I pop the 4" lid and drop in the hops. Purge several times and be done with it. If I'm happy with the results I'm gonna continue this way.

 

[Vale71]

I can't help but wonder how you guys that feel bottled CO2 is terrible intend to serve your beer? If you can't use bottled CO2 and obviously can't invest a couple o mils for a CO2 recovery plant are you then just going to drink the whole batch in a single sitting while dispensing with gravity only? Unless you can pull that off then you will have to use your bottled CO2 to push the beer out and then your beer is ruined. Wonder how the whole beverage industry deals with issue as well?
Truth is food-grade CO2 has very low levels of residual O2 that are deemed to be low enough by the industry. If some of you are buying very low purity, non food-grade CO2 then you cannot make the assumption that everybody else is.

 

[eric19312]

I can't help but wonder how you guys that feel bottled CO2 is terrible intend to serve your beer? If you can't use bottled CO2 and obviously can't invest a couple o mils for a CO2 recovery plant are you then just going to drink the whole batch in a single sitting while dispensing with gravity only? Unless you can pull that off then you will have to use your bottled CO2 to push the beer out and then your beer is ruined. Wonder how the whole beverage industry deals with issue as well?
Truth is food-grade CO2 has very low levels of residual O2 that are deemed to be low enough by the industry. If some of you are buying very low purity, non food-grade CO2 then you cannot make the assumption that everybody else is.

I believe this article is a key source of the concern. It was for me.
http://www.********************/brewing-methods/carbon-dioxide-purity/
The underlying idea is that all sources of post fermentation oxygen ingress are additive. So even if the net contribution of O2 from the CO2 used to carbonate the beer is small, it is additive to other sources of O2 ingress that you are less able to control. Yep you are going to need commercial CO2 to push the beer from the keg to the glass but it is an option to carbonate via spunding instead of force carbing. Same rationale gets applied to using fermentation gas to purge kegs.

Still as far as I can tell it is all theory and math and nobody has shown with a sufficiently sensitive DO meter that spunding results in a measurable difference in TPO. I'm sitting at the edge of the rabbit hole looking in but as of right now I'm force carbing a batch of IPA in my fermentor using commercial beverage grade CO2 and a carb stone.

 

[doug293cz]

I believe this article is a key source of the concern. It was for me.
http://www.********************/brewing-methods/carbon-dioxide-purity/
The underlying idea is that all sources of post fermentation oxygen ingress are additive. So even if the net contribution of O2 from the CO2 used to carbonate the beer is small, it is additive to other sources of O2 ingress that you are less able to control. Yep you are going to need commercial CO2 to push the beer from the keg to the glass but it is an option to carbonate via spunding instead of force carbing. Same rationale gets applied to using fermentation gas to purge kegs.

Still as far as I can tell it is all theory and math and nobody has shown with a sufficiently sensitive DO meter that spunding results in a measurable difference in TPO. I'm sitting at the edge of the rabbit hole looking in but as of right now I'm force carbing a batch of IPA in my fermentor using commercial beverage grade CO2 and a carb stone.

The problem with DO and TPO measurements it that they cannot tell you how much O2 damage has already been done (how much O2 has already reacted with beer components.) They can only tell you how much free O2 is currently available to react in the future.

Brew on

 

[jerrylotto]

What I don't understand is why all of these calculations are done assuming perfect mixing. Carbon dioxide is denser (heavier) than air and if you introduce it at the bottom of a keg or fermenter slowly, it should displace the air inside - not mix. Have you ever experimented with open bucket fermentation? As long as you are in a room with little or no air movement, it is totally practical and it promotes off-gassing and ester formation.

 

[mongoose33]

What I don't understand is why all of these calculations are done assuming perfect mixing. Carbon dioxide is denser (heavier) than air and if you introduce it at the bottom of a keg or fermenter slowly, it should displace the air inside - not mix. Have you ever experimented with open bucket fermentation? As long as you are in a room with little or no air movement, it is totally practical and it promotes off-gassing and ester formation.

Actually, you don't get that "blanket" of CO2. The O2 and CO2 (and trace gases) mix. There's a nice explanation of that (including a video showing how it works) here somewhere. I think @doug293cz might have posted it, not certain.

If I find it I'll edit it in here. EDITED TO ADD: Help! Leaky fermentation bucket lid

The link to the Youtube video in the above post is broken, so here it is:

Very eye-opening.

There's this popular misconception about CO2 forming a "blanket" because it's denser. I suspect that comes from people's experience with dry ice which, when it escapes a container, curls over the edge and moves downward.

From what I've read, that's not really CO2 you see doing that; it's water vapor, and it's heavier because it's colder.

 

[Vale71]

From what I've read, that's not really CO2 you see doing that; it's water vapor, and it's heavier because it's colder.

And also because it's a liquid (water) and no longer a gas (water vapor). Water vapor is, like most gases, completely invisible. Once it turns into water droplets it becomes visible as clouds or fog.

Gases mix and quite rapidly at normal temperatures but I guess the CO2 "blanket" myth will never really die out.

 

[Rainy]

I always heard the CO2 "blanket" myth only holds for active fermentation, so when you have actively CO2 escaping out of the liquid, but maybe even that depends on the speed of CO2 production in the liquid. I guess near the end of fermentation the timescale of diffusion of oxygen molecules starts to become smaller than that of the movement of CO2 from the liquid to the gas phase, hence diffusion of O2 becoming faster than the CO2 moving out of the liquid. Finally resulting in O2 being able to reach the liquid-gas interface.

 

[Vale71]

You need quite a high flow rate to mechanically push other gases back faster than they diffuse, like what you would get out of a CO2 bottle. Even during fermentation gases are thoroughly mixed and the O2 level drops slowly as more and more gas is expelled through the airlock. At best if CO2 production is really high you could have a concentration gradient that you would need rather sophisticated equipment to measure.

 

[jerrylotto]

I am primarily thinking about the discussion of purging an empty keg or fermenter - and tat standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m3, about 1.67 times that of air.

 

[Vale71]

I am primarily thinking about the discussion of purging an empty keg or fermenter - and tat standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m3, about 1.67 times that of air.

Molecular weight only influences the rate of diffusion, with lighter gases diffusing faster than heavier ones. No gas can "float" on another gas. To have buoyancy you need displacement and to have displacement you need a solid object, like a boat or an airship. Gases don't displace each other, they just mix.

 

[doug293cz]

I am primarily thinking about the discussion of purging an empty keg or fermenter - and tat standard temperature and pressure, the density of carbon dioxide is around 1.98 kg/m3, about 1.67 times that of air.

Watch the video. Br2 is 3.6 times heavier than CO2, and it mixes completely with air in about 30 minutes. In the 2nd example, NO2 is about the same density as CO2, and you can see that it homogenized with air much more quickly than does Br2.

Brew on

 

[Bobo1898]

Great thread, got lost in it this morning. Because of O2, I've tended to dry hop at the end of fermentation, but still don't like opening my lid (Ss Brewtech Brew Bucket) because it's very exposed.

I do like the magnet idea, as it's most ideal for my setup. Was thinking I could use a silicone cup and magnets and then turn the magnet to turn the cup to dump the hops into the beer when it's time to dry hop. Cup and magnet should stay out of the beer.

Just wondering if I should be concerned about loss of aroma with CO2 being pushed out?

 

[Jag75]

When I dry hop in my CF5 I just run co2 as I set the hops in . Easy peasy .

 

[okiedog]

When I dry hop in my CF5 I just run co2 as I set the hops in . Easy peasy .

Lucky dog! Conicals are great, but pricy. I'm jealous!

 

[Jag75]

Lucky dog! Conicals are great, but pricy. I'm jealous!

They are pricey but worth every penny imo . Spike offers monthly payments , thats what I did . Low payments but it helps to pay bigger chunks .

 

[Barleymist]

I like the magnet ideas, I do not have food safe magnets or vacuum sealers though. A simple idea I plan to use in my 15g Fermzilla is a "Hop Ship." Place a small stainless or PET plastic bowl filled with hops and float it on wort surface before sealing tank. To incorporate hops, agitate vessel and sink the Hop Ship. (I have a hop filter on pickup tube so I do not need a hop bag, but that can go in bowl too. Small mouth carboys does not work.)