Length of Carbonating Keg with Priming Sugar

[O1DMBFan]

We've recently switched to priming sugar for our method of carbonating our kegs. This thread is not to discuss the merits of force carbing, please do not respond to my questions about priming sugar methods with force carbing methods, thanks in advance.

So, we prime with sugar that's been dissolved in boiling water. Purge the head space with CO2 and then store at room temperature for x amount of days. That X is my problem, I'd like to know when I should assume the keg is properly conditioned. I am not satisfied with using an over estimate by just saying wait 2-3 weeks. I have a 6" gas line with a pressure gauge on one end and a gas in keg attachment on the other. I frequently check the pressure of the keg and can see it raise as the days pass.

1. Should I release pressure as it get's higher and higher (20psi)? I'm a bit nervous the high pressure is not a healthy yeast environment. When it get's to 20psi+ I've been releasing the pressure down to about 9psi.

2. Is it the proper time to chill, when the pressure holds steady for 2-3 days with no increase?

I've looked all over these, and other, forums and have been unable to find any information regarding the monitoring of a keg that's been primed with sugar. Any and all help would be appreciated. Thanks!

 

[hunter_le five]

Why would you release pressure? You don't release pressure on bottle-carbed beers, so why would you do it when natural-carbing in a keg? You probably need ~30psi at room temp in order to get an adequate carbonation level dissolved into solution. If you keep venting it, you are going to end up with severely under-carbed beer.

 

[O1DMBFan]

Why would you release pressure? You don't release pressure on bottle-carbed beers, so why would you do it when natural-carbing in a keg?

Wow, what a good point, not sure why I hadn't thought about it that way. Kind of an "oh doy" moment. Thanks for pointing it out haha.

So, if once the keg has reached 30psi (at room temp) I can expect good carbonation and can chill? Or should it sit at 30psi for a certain amount of time?

 

[Dolomieu]

We've recently switched to priming sugar for our method of carbonating our kegs. This thread is not to discuss the merits of force carbing, please do not respond to my questions about priming sugar methods with force carbing methods, thanks in advance.

So, we prime with sugar that's been dissolved in boiling water. Purge the head space with CO2 and then store at room temperature for x amount of days. That X is my problem, I'd like to know when I should assume the keg is properly conditioned. I am not satisfied with using an over estimate by just saying wait 2-3 weeks. I have a 6" gas line with a pressure gauge on one end and a gas in keg attachment on the other. I frequently check the pressure of the keg and can see it raise as the days pass.

1. Should I release pressure as it get's higher and higher (20psi)? I'm a bit nervous the high pressure is not a healthy yeast environment. When it get's to 20psi+ I've been releasing the pressure down to about 9psi.

2. Is it the proper time to chill, when the pressure holds steady for 2-3 days with no increase?

I've looked all over these, and other, forums and have been unable to find any information regarding the monitoring of a keg that's been primed with sugar. Any and all help would be appreciated. Thanks!

So you cant get no satisfaction??

If i were to naturally carb a keg i would expect it to take just as long as a bottle would, or at least that is where I would start. Track your pressure gauge but know that before equilibrium is found that it will probably be higher in the head space before dissolving in to the beer. You may have to blaze this trail yourself, by tracking the pressure for X number of days. I would start at three weeks, then creep down. Though if you have a keezer you can check it when ever and fall back on force carbing if you miss the "moment".

Also whats with the tude about force carbing? I'm just curious as it's what most people do when they are seemingly in a rush, which you seem to be in.

 

[hunter_le five]

I know you don't want to hear it, but... I would let it sit for 3 weeks before I chilled it.

When the yeast starts eating the priming sugar, it's initially going to build up a lot of pressure in the headspace. It takes time (and a constant application of pressure) for that CO2 to be dissolved into the liquid, and for the beer and headspace to reach equilibrium. And it takes time for the yeast to eat all the sugar and produce an adequate level of carbonation.

Just because you have 30psi in the headspace doesn't mean you have enough gas in there to adequately carb a beer, so do not assume that. When I say "you need 30psi", that's not a volume or amount of gas, that's a pressure level. Carbonation absorption in beer is a function of pressure, temperature, and time. Give it some time and don't rush the process.

Edit: I don't know what level of pressure will be achieved when natural carbing. ~30psi at room temp is what I would set it to when using a force-carb setup, so that is the "equilibrium" pressure. Realistically when natural carbing, the pressure will likely spike upwards of that figure and come back down as equilibrium between beer and headspace is achieved (as the gas dissolves into solution).

 

[O1DMBFan]

I was thinking since I haven't seen a write up on it, that I may be forging my own write up soon enough. Thanks for the info, I think I'll start a trial and error process.

Also whats with the tude about force carbing? I'm just curious as it's what most people do when they are seemingly in a rush, which you seem to be in.

We force carbed for a while, I by no means think it's a bad route. We're just experimenting and trying out what works best. We found at the rate of batches we're turning out we were filling our CO2 tanks more often than we'd prefer. Every time we fill, we have to take a bit of a drive. We don't mind taking our time with keg priming, not in a hurry at all. I just am a fan of precision and want to KNOW when it's ready, not the best route to GET it ready the fastest.

If I do indeed start this experiment I'll be sure to document well and post a write up eventually. Kegging another batch Saturday so I'll start with that fresh keg and see what we get. All recommendations and suggestions are welcome as I forge ahead.

 

[Bobby_M]

That's two people in a row that think the CO2 builds in the headspace but somehow is not also in the beer, dissolved as equilibrium. This is one of those brewing myths that continues with no basis. The CO2 is being generated in the beer at the molecular level when the yeast are making it. It's the opposite of forcing CO2 into the headspace and waiting for it to dissolve into the beer. Long story short, I contend that when you see 30psi on that gauge at room temp, you're pretty much done.

 

[grittanomyces]

Also whats with the tude about force carbing? I'm just curious as it's what most people do when they are seemingly in a rush, which you seem to be in.

+1, if you're going to naturally carb, then you'll have to have patience, and give it at least a week, if not 2 or 3 in many cases.

If you don't want to wait that long, then hook it up to CO2 just to pour a sample, and see if it's carbed to your satisfaction yet. If not, remove from CO2 and wait. It's not any different from bottle-carbing, that if you don't want to give it more than enough time, then you will only know if it's ready by sampling around a week.

As far as I can tell, there is no exact time when your beer will carbonate, only that it will tend to take longer with high gravity brews. It's no different than force-carbing, you will only know for sure by sampling (unless someone here can offer a better way to tell, but beer works on it's own schedule, and testing/tasting is the only way to know at any stage that it's ready for the next step).

 

[O1DMBFan]

I know you don't want to hear it, but... I would let it sit for 3 weeks before I chilled it.

When the yeast starts eating the priming sugar, it's initially going to build up a lot of pressure in the headspace. It takes time (and a constant application of pressure) for that CO2 to be dissolved into the liquid, and for the beer and headspace to reach equilibrium. And it takes time for the yeast to eat all the sugar and produce an adequate level of carbonation.

Just because you have 30psi in the headspace doesn't mean you have enough gas in there to adequately carb a beer, so do not assume that. When I say "you need 30psi", that's not a volume or amount of gas, that's a pressure level. Carbonation absorption in beer is a function of pressure, temperature, and time. Give it some time and don't rush the process.

Edit: I don't know what level of pressure will be achieved when natural carbing. ~30psi at room temp is what I would set it to when using a force-carb setup, so that is the "equilibrium" pressure. Realistically when natural carbing, the pressure will likely spike upwards of that figure and come back down as equilibrium between beer and headspace is achieved (as the gas dissolves into solution).

Thanks for the recommendation, I agree, I don't want to rush the process, that's why I'm trying to find a way to measure when it would be complete.

I agree with the logic that the psi will climb and climb until the yeast are about done and the CO2 is no longer being created. This would be our peak and then the solution would continue to absorb the CO2 and the pressure will begin to fall.

Is there a way to either measure or calculate the CO2 level of the actual solution at any given time?

Thanks again everyone for bearing with my unyielding questions. That's what's great about this hobby and the community that comes with it, all questions are welcomed.

 

[Stealthcruiser]

Sub'd.
Post it here when you do your "study", Please Sir!

 

[hunter_le five]

Is there a way to either measure or calculate the CO2 level of the actual solution at any given time?

I haven't the foggiest.

What you are proposing (finding some way to tell via objective measurement if a natural carb is complete) is uncharted territory as far as I know (which admittedly is not very far).

I've never "measured" a natural carbonation; I always just sample it every few days until it *seems* right. In my totally nonscientific experience, rarely is it ready in less than 2 weeks, and it's almost always ready by 3 weeks. Apart from that, I don't know, I almost exclusively force-carb these days. At any rate, yeast are biological creatures, and don't tend to work on a fixed schedule.

But if you're going to experiment, take good notes and let us know what you find out.

 

[grittanomyces]

Now I'm curious.

Does anyone know if it does use much CO2 at all if you force carb? Assuming no leaks, it seems like the CO2 would not have to replace that much of itself as it went into the beer, not anything significant at all compared to the normal keg processes of pouring and venting, which would seem to be where most of your CO2 is used.

Am I off base?

 

[Dolomieu]

That's two people in a row that think the CO2 builds in the headspace but somehow is not also in the beer, dissolved as equilibrium. This is one of those brewing myths that continues with no basis. The CO2 is being generated in the beer at the molecular level when the yeast are making it. It's the opposite of forcing CO2 into the headspace and waiting for it to dissolve into the beer. Long story short, I contend that when you see 30psi on that gauge at room temp, you're pretty much done.

I wouldn't think that there would be 100% of the CO2 escaping to the head space causing the pressure prior to dissolving in to solution. Though I would expect that there would be a rise prior to finding equilibrium do to the temperature of the beer and the CO2's desire to not be dissolved at the temperature and pressure. I don't have data to back that up of course. How much of a rise I don't know. Which is why waiting seems prudent.

Could you point to a myth busting article or anything? I would be interesting in reading it if you know of one. I'm always willing to learn.

 

[hunter_le five]

That's two people in a row that think the CO2 builds in the headspace but somehow is not also in the beer, dissolved as equilibrium. This is one of those brewing myths that continues with no basis. The CO2 is being generated in the beer at the molecular level when the yeast are making it. It's the opposite of forcing CO2 into the headspace and waiting for it to dissolve into the beer. Long story short, I contend that when you see 30psi on that gauge at room temp, you're pretty much done.

I would think that CO2 is expelled into the headspace more readily than than it is absorbed by the beer (produced faster than the beer can absorb it). It takes time for beer to absorb CO2, whereas it takes very little time to compress gas into an empty space.

I can pump 30psi into the headspace of my flat beer keg until the headspace reaches 30psi and disconnect the gas, but it's going to take a while for equilibrium to be achieved between the beer and the headspace.

I'm not saying that some CO2 absorption in the beer isn't happening the entire time, but I wouldn't expect perfect equilibrium until the end of the process.

I could be wrong, just my thoughts. As I said I've never actually tried measuring a natural carb, but would be interested to hear the data from someone who has.

 

[Bobby_M]

I would think that CO2 is expelled into the headspace more readily than than it is absorbed by the beer (produced faster than the beer can absorb it). It takes time for beer to absorb CO2, whereas it takes very little time to compress gas into an empty space.

I can pump 30psi into the headspace of my flat beer keg until the headspace reaches 30psi and disconnect the gas, but it's going to take a while for equilibrium to be achieved between the beer and the headspace.

I'm not saying that some CO2 absorption in the beer isn't happening the entire time, but I wouldn't expect perfect equilibrium until the end of the process.

I could be wrong, just my thoughts. As I said I've never actually tried measuring a natural carb, but would be interested to hear the data from someone who has.

Since the source of CO2 during natural carbonation is yeast fermentation, the CO2 molecules are already in individual contact with the H2O in the beer which is a prime situation for carbonation. Think about how putting CO2 into fine bubbles makes it dissolve that much faster. Now take those micro bubbles and split them into even finer bubbles, all they way down to single CO2 molecules. In other words, it would dissolve before it could get to the surface. When the concentration of Co2 in solution exceeds its equilibrium with the headspace then it should effervesce into the headspace until they are equal again.

That means that during natural carbonation, the amount of CO2 in solution would always be greater than or equal to the amount of CO2 in the head space.

The reason I think this is so counter intuitive is because everyone that thinks or talks about carbonation as a process thinks from a force carbonation perspective where there is a long equilibrium delay because the surface area between the headspace and beer is minimal.

The way to test this is to monitor the pressure gauge during the entire process while putting very stringent control on ambient temp. If I'm right, the pressure should ramp up and then plateau forever. If conventional instinct is correct, it would ramp up, plateau and then drop a bit before normalizing. Someone did test this last year (i can't find the thread) and they did a pretty good job of it but the temperature controls were a little too loose. If the headspace is allowed to vary in temp separate from the beer, you can get false pressure spikes that are not related to co2 movement.

It really doesn't matter all that much but it's fun to think about.

 

[Dan]

I can't even believe I'm going to try and post here. Im in a place about 20,000 leagues above me.

Somebody on this sight put a pressure gauge on a bottle of naturally carbonating beer. If I remember correctly. The pressure peaked and then dropped down. I don't know about his temp control but it was fairly consistent.

Hopefully he'll chime in on this thread with the results of his experiment. He's pretty humble though. He might not add his input.

 

[hunter_le five]

Since the source of CO2 during natural carbonation is yeast fermentation, the CO2 molecules are already in individual contact with the H2O in the beer which is a prime situation for carbonation. Think about how putting CO2 into fine bubbles makes it dissolve that much faster. Now take those micro bubbles and split them into even finer bubbles, all they way down to single CO2 molecules. In other words, it would dissolve before it could get to the surface. When the concentration of Co2 in solution exceeds its equilibrium with the headspace then it should effervesce into the headspace until they are equal again.



That means that during natural carbonation, the amount of CO2 in solution would always be greater than or equal to the amount of CO2 in the head space.



The reason I think this is so counter intuitive is because everyone that thinks or talks about carbonation as a process thinks from a force carbonation perspective where there is a long equilibrium delay because the surface area between the headspace and beer is minimal.



The way to test this is to monitor the pressure gauge during the entire process while putting very stringent control on ambient temp. If I'm right, the pressure should ramp up and then plateau forever. If conventional instinct is correct, it would ramp up, plateau and then drop a bit before normalizing. Someone did test this last year (i can't find the thread) and they did a pretty good job of it but the temperature controls were a little too loose. If the headspace is allowed to vary in temp separate from the beer, you can get false pressure spikes that are not related to co2 movement.



It really doesn't matter all that much but it's fun to think about.

Interesting, you make some very good points I hadn't considered initially.

OP, if you're willing to do some observation and data gathering, there is a very interesting experiment here to try.


Sent from my iPad using Home Brew

 

[O1DMBFan]

You can definitely count on a follow up report following this weekends kegging. I'll keep you guys posted, sub for updates.

 

[Bobby_M]

I can't even believe I'm going to try and post here. Im in a place about 20,000 leagues above me.

Somebody on this sight put a pressure gauge on a bottle of naturally carbonating beer. If I remember correctly. The pressure peaked and then dropped down. I don't know about his temp control but it was fairly consistent.

Hopefully he'll chime in on this thread with the results of his experiment. He's pretty humble though. He might not add his input.

That was the one I was remembering. In that thread I questioned the temp control. I know there was a temp logger used but nothing was keeping the temps solid. I always meant to copy the experiment with tighter controls but just never had the time. If someone wants to try it, submerge the entire container including the headspace into a larger body of water to keep temps more buffered.

 

[Dolomieu]

That was the one I was remembering. In that thread I questioned the temp control. I know there was a temp logger used but nothing was keeping the temps solid. I always meant to copy the experiment with tighter controls but just never had the time. If someone wants to try it, submerge the entire container including the headspace into a larger body of water to keep temps more buffered.

I would think even just having it in a fermentation chamber would be more than adequate. I need to brew soon and have a gauge I could hook up. Maybe I'll give this a try just to see. You make great points and it is fun to think about.

 

[JuanMoore]

We've recently switched to priming sugar for our method of carbonating our kegs. This thread is not to discuss the merits of force carbing, please do not respond to my questions about priming sugar methods with force carbing methods, thanks in advance.

So, we prime with sugar that's been dissolved in boiling water. Purge the head space with CO2 and then store at room temperature for x amount of days. That X is my problem, I'd like to know when I should assume the keg is properly conditioned. I am not satisfied with using an over estimate by just saying wait 2-3 weeks. I have a 6" gas line with a pressure gauge on one end and a gas in keg attachment on the other. I frequently check the pressure of the keg and can see it raise as the days pass.

1. Should I release pressure as it get's higher and higher (20psi)? I'm a bit nervous the high pressure is not a healthy yeast environment. When it get's to 20psi+ I've been releasing the pressure down to about 9psi.

2. Is it the proper time to chill, when the pressure holds steady for 2-3 days with no increase?

I've looked all over these, and other, forums and have been unable to find any information regarding the monitoring of a keg that's been primed with sugar. Any and all help would be appreciated. Thanks!

1) NO! I realize it's been covered, but if you release any pressure at any point, your resulting carbonation level will be less than whatever you calculated/planned on with the amount of priming sugar you added.

2) Not necessarily. There could be a stall if your "room temp" is on the cool side, or even a decrease in presure before it's fully carbed if there are temp fluctuations of more than a couple degrees.

You'll know it's fully carbed when the pressure reaches whatever corresponds to the beer temp and your desired carb level. For example, at 78° and a desired carb level of 2.5 vol it would be 33.6 psi. This is very different from "proper conditioning" though, which is what you asked about. Minimum time for proper conditioning depends highly on the style of beer and ABV. Just because it's fully carbed doesn't mean it's time to chill it and start drinking.