No oxygen dry hopping

[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.lowoxygenbrewing.com/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.lowoxygenbrewing.com/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.)

 

[jerrylotto]

Don't let the krausen rock your boat . I've had a few fermentations that have been so active that nothing would have remained afloat!

Even without a vac sealer, you could stuff a magnet into a balloon, eject most of the air and tie it off.

 

[eric19312]

So after struggling with the Norcal yeast brink I've decided to try Mongoose's dry hopper. Only I supersized it. The components from top to bottom are:
3" TC with 2 ball lock posts and PRV
3" TC sight glass that came with my Norcal yeast brink
3" TC butterfly valve
4" x 3" TC Concentric Reducer

edited to reduce file size

 

[eric19312]

and here it is on the CF15. Current batch is at high krausen I will add dry hops in about a week.

 

[FswBG]

@eric19312 whoah that thing’s a beast! It really makes me look forward to the 3 port lid.

What problems did you have with the brink if you don’t mind sharing? I’m interested in one, but I’m racking my brain why they don’t add a PRV. I would think using the built in “exhaust port” to purge would become cumbersome pretty quick.

 

[eric19312]

I purge it by loosening the TC between the brink and the butterfly valve and running in gas for a while but a PRV might be easier. But how would you purge the gas out of the downcomer tube? I think that would trap some air that wouldn't be easy to purge without loosening the TC anyway. Maybe the PRV would work if it could be at top of the downcomer pipe near the TC connection to the fermentor.

Still that is not the issue that pushed me to try this setup. The issue is getting sufficient quantity of the hop pellets up into the fermentor. With the 3" brink I've been able to push in 4oz at a time. The first addition is not too bad. Following Jaybird's suggestion to trim half an inch off the bottom of the downcomer pipe I could get the first 4oz into the fermentor in an hour or two. Load the hops, purge the hops, flood the brink, wait 30-45 minutes and then push. That would get maybe 3/4 of the hops into the tank, so I'd flood the brink again, wait another 30 min and push, now most of the hops are into the tank, might need one more cycle. Now for the next 4oz. Clean the brink and let it drip dry. Add 4 more oz hops. Purge and flood. Wait and push. Oops even waiting an hour on the second batch of hops they don't want to be pushed up...what is going on...more pressure...lots more pressure (what is this sight glass rated for anyway? I've gone pretty high but it scares me to do that)...open and close the butterfly...finally they start to move...maybe 1/4 goes up...flood again, wait..push...maybe repeat 6 times to get 80-90% of the hops into the fermentor. Have to bleed CO2 out of the headspace will all that pushing. What is going on? My theory is that while the first slug of hops gets up there ok, when you flood the second slug of hops you are flooding it with a mixture of beer and hops. Maybe the answer is you can push 4oz of hops first go and only 2oz at a time after that.

So I've got 16-17 gallons of beer in the tank. Typical dry hop quantities in current IPA recipes run 1-2 oz per gallon (and I've seen higher than that) I need to get 1-2 pounds into the fermentor. Just not going to happen. I think best I've managed was about 12oz and that took a couple days.

 

[FswBG]

I purge it by loosening the TC between the brink and the butterfly valve and running in gas for a while but a PRV might be easier. But how would you purge the gas out of the downcomer tube? I think that would trap some air that wouldn't be easy to purge without loosening the TC anyway. Maybe the PRV would work if it could be at top of the downcomer pipe near the TC connection to the fermentor.

Still that is not the issue that pushed me to try this setup. The issue is getting sufficient quantity of the hop pellets up into the fermentor. With the 3" brink I've been able to push in 4oz at a time. The first addition is not too bad. Following Jaybird's suggestion to trim half an inch off the bottom of the downcomer pipe I could get the first 4oz into the fermentor in an hour or two. Load the hops, purge the hops, flood the brink, wait 30-45 minutes and then push. That would get maybe 3/4 of the hops into the tank, so I'd flood the brink again, wait another 30 min and push, now most of the hops are into the tank, might need one more cycle. Now for the next 4oz. Clean the brink and let it drip dry. Add 4 more oz hops. Purge and flood. Wait and push. Oops even waiting an hour on the second batch of hops they don't want to be pushed up...what is going on...more pressure...lots more pressure (what is this sight glass rated for anyway? I've gone pretty high but it scares me to do that)...open and close the butterfly...finally they start to move...maybe 1/4 goes up...flood again, wait..push...maybe repeat 6 times to get 80-90% of the hops into the fermentor. Have to bleed CO2 out of the headspace will all that pushing. What is going on? My theory is that while the first slug of hops gets up there ok, when you flood the second slug of hops you are flooding it with a mixture of beer and hops. Maybe the answer is you can push 4oz of hops first go and only 2oz at a time after that.

So I've got 16-17 gallons of beer in the tank. Typical dry hop quantities in current IPA recipes run 1-2 oz per gallon (and I've seen higher than that) I need to get 1-2 pounds into the fermentor. Just not going to happen. I think best I've managed was about 12oz and that took a couple days.

Oh okay, that’s how I purge as well using a 2” sight glass to TC with ball lock, which has been manageable, but I was thinking the brink was a bit more refined.

On the long dry hop sessions, I feel for you. That sounds horribly cumbersome. I suspect the long downpipe as the issue. I would think 4oz is pretty dense and needing to travel up that tube, through the valve, against that much volume of beer only by CO2 pressure.. forget it. I’m sure it works great as a brink for yeast/spices/finings. (I still think a Prv instead of exhaust port would be ideal so the you could purge quicker and easier)

I have not found an easy way to add hops from below either, but I thought it was due to only having a 2” SG instead of a larger brink. Good to know. I chuckled when I received the spike 3 port lid email and saw all the lid “Do not do this!” pictures. Yep, I have tried a few of those methods. Being careful of course and aware of the danger. DH is just much easier when you’re not fighting gravity.
Anyways, I like your setup. I’m interested to hear how it goes next week. I wish Spike would make one of the 2 new lid ports a 2” instead of 1.5 for those of us using glycol. I mean cmon!

 

[eric19312]

I’m interested to hear how it goes next week. I wish Spike would make one of the 2 new lid ports a 2” instead of 1.5 for those of us using glycol. I mean cmon!

I'm thinking they should design a chilling coil that bridges two of those 1.5" TC ports. Then you could use the larger 4" port for more interesting things.

edited to add: or just uses one of the 1.5" ports would be even better. Might be tight fit to get it all on there but...

 

[DuncB]

Looking at this as a non user of this equipment I must be missing something in the process pathway.

If you didn't have the blow off tube, couldn't you put a spunding valve on the top of the sight glass thing to let gas out ie purge. Then close butterfly. Add hops repeat purge via injected CO2 and then by cracking butterfly open and then drop hops?
Or inject CO2 via the blow off tube to do the purge from inside out?

 

[eric19312]

Looking at this as a non user of this equipment I must be missing something in the process pathway.

If you didn't have the blow off tube, couldn't you put a spunding valve on the top of the sight glass thing to let gas out ie purge. Then close butterfly. Add hops repeat purge via injected CO2 and then by cracking butterfly open and then drop hops?
Or inject CO2 via the blow off tube to do the purge from inside out?

If that is directed to me...Pretty sure that is what I plan to do. I swap the blow off tube for the pressure manifold once fermentation slows down. I put a spunding valve on the manifold to hold pressure around 3 PSI while the beer finishes and the yeast drops. I do plan to move the spunding valve to the sight glass and flow CO2 from the gas manifold up through the sight glass when I just crack open the butterfly on the sight glass to purge the dry hopper of any residual oxygen. I didn't think I really needed two ball lock posts and a PRV on the sight glass but that fitting was premade for another application and only about $10 more than a fitting with just one ball lock post and no PRV.

 

[DuncB]

Not directed at anyone in particular, just trying to get my head around it. Definitely want something with a PRV and good volume for those hops and you've nailed it.