Keg Conditioning

[x3la]

I'm interested in learning how others keg condition with priming sugar, as opposed to force carbonating.

After conditioning, how long do you refrigerate before tapping?

Would tapping without refrigerating for long enough (a few days) potentially lead to a very foamy beer?

 

[mac_1103]

First of all, don't believe anything you read about using less priming sugar for a keg than you would for bottles. A keg is just a very large bottle so prime it the same way. I usually let mine go for about 3 weeks at ambient and then a week in the fridge. Both are probably longer than necessary, but I think the patience pays off in clearer beer.

 

[hilljack13]

I have a similar question, not trying to hijack the thread or anything, but if I only have one CO2 tank would it be feasible to transfer to keg without carbonating let it condition while flat, then carb with CO2?

 

[Dr_Jeff]

I have a similar question, not trying to hijack the thread or anything, but if I only have one CO2 tank would it be feasible to transfer to keg without carbonating let it condition while flat, then carb with CO2?

You probabally should add a bit of CO2 to get the lid to seat, but you can do it that way.
If you are going to let it condition, why not add the priming sugar and let it carbonate at the same time?
The yeast will consume the small amount of sugar in a few days anyway.

 

[hilljack13]

You probabally should add a bit of CO2 to get the lid to seat, but you can do it that way.
If you are going to let it condition, why not add the priming sugar and let it carbonate at the same time?
The yeast will consume the small amount of sugar in a few days anyway.

Thanks. I guess my thinking was if I am going to carb with CO2 then I didn't want to put any added sugar. I see what you say about adding some to keep the lid tight. I had not thought of that.

 

[Want2Brew]

I usually prime the keg with corn sugar after filling, install the lid, apply Co2 to seat the lid and purge the head space a few times to reduce the chance of oxidation.

To the OP: it is likely that after only a few days at serving temp that the beer has not absorbed enough of the Co2/pressure in the head space of the keg. Serving or pouring at a higher pressure could lead to excessive foaming. In my experience it is best to wait a week or so after refrigerating to serve. Hope this helps!

cheers!

 

[govner1]

You probabally should add a bit of CO2 to get the lid to seat, but you can do it that way.
If you are going to let it condition, why not add the priming sugar and let it carbonate at the same time?
The yeast will consume the small amount of sugar in a few days anyway.

You should definitely pressuriz your keg to seal the lid so that you capture the CO2 generated by the yeast metabolizing whatever your choice of fermentable is whether it’s priming sugar, DME, or even cane sugar.
Palmer has a chart with suggested amounts of each. He does recommend only 4 oz of cane sugar and in my experience it is perfect.
I disagree with @mac_103 as to the amount of priming sugar/DME when keg conditioning vs. bottling. I use about .75 oz per gallon (25% less) when keg conditioning. It’s has been very satisfactory for over a decade.

 

[mac_1103]

Palmer has a chart with suggested amounts of each. He does recommend only 4 oz of cane sugar and in my experience it is perfect.

4 oz of cane sugar in 5 gallons is about 2.35 volumes of CO2, which is perfect for many styles.

I disagree with @mac_103 as to the amount of priming sugar/DME when keg conditioning vs. bottling. I use about .75 oz per gallon (25% less) when keg conditioning. It’s has been very satisfactory for over a decade.

Please explain the biology that allows the yeast to generate the same amount of CO2 from less sugar. Or the physics that allows less CO2 to carbonate the beer to a higher level in a keg than it would in a bottle. You can't because there is no such biology or physics. The fact is that you are under-carbonating your beer if you use less sugar in a keg than you would in bottles. You're getting satisfactory results because you make up the missing CO2 when you hook the keg up to a cylinder to serve.

 

[govner1]

My oh! my aren’t we sensitive when someone dares to disagree with you!
There are , in fact, some very good reasons to reduce the fermentable that you use when keg conditioning that result in better results. First, the amount of dissolved CO2 in 5 gallons of beer (keg) is higher than in a 12 oz bottle. This will be absorbed once the beer is chilled. Secondly, you are better able to prevent over carbonation and once you chill the keg and hook it up you are much less likely to have a foam (or bottle) bomb on your hands. I personally find that the overall mouthfeel is superior to force carbing at 15+lbs and again much less risk of over carbonation.
It’s not biology, but there’s definitely some physics involved!
Salut!

 

[mac_1103]

My oh! my aren’t we sensitive when someone dares to disagree with you!

You can disagree with me all you want. But you can't disagree with biology or physics.

the amount of dissolved CO2 in 5 gallons of beer (keg) is higher than in a 12 oz bottle

Not per unit volume it isn't.

You're deliberately under-priming and then finishing it by force carbonation. Go ahead and do that if you want. Just don't pretend that there's something magic going on with priming sugar in a keg vs a bottle.

 

[doug293cz]

My oh! my aren’t we sensitive when someone dares to disagree with you!
There are , in fact, some very good reasons to reduce the fermentable that you use when keg conditioning that result in better results. First, the amount of dissolved CO2 in 5 gallons of beer (keg) is higher than in a 12 oz bottle. This will be absorbed once the beer is chilled. Secondly, you are better able to prevent over carbonation and once you chill the keg and hook it up you are much less likely to have a foam (or bottle) bomb on your hands. I personally find that the overall mouthfeel is superior to force carbing at 15+lbs and again much less risk of over carbonation.
It’s not biology, but there’s definitely some physics involved!
Salut!

Emphasis added to quote.

Please elaborate, including equations and formulas where appropriate, how the physics, chemistry and/or biology are different in bottles vs. kegs. I have challenged people previously to provide such an explanation, and no one has been able to do so.

Brew on

 

[ba-brewer]

Half the amount of sugar works fine for me when kegging, but I think because I keg in under 10days the beer might still not be all the way to TG. Think I seen @doug293cz post that it only takes a gravity point of extra attenuation to cause trouble.

I am also quite surprised at the amount of CO2 in my beer on transfer sometimes, makes me wonder if the CO2 has not yet fully came to equilibrium so I have more volumes than the temp chart suggest.

 

[Zambezi Special]

I've always wondered why there would be a difference in sugar amount for bottle vs keg.

But to be safe, I've used the lower amount and have had to top up with CO2

I think I will put the full amount next time, leave to carbonate long enough (2+ weeks) and attach a spunding valve to check progress & for safety

 

[McMullan]

Emphasis added to quote.

Please elaborate, including equations and formulas where appropriate, how the physics, chemistry and/or biology are different in bottles vs. kegs. I have challenged people previously to provide such an explanation, and no one has been able to do so.

Brew on

I’ve always assumed it was associated with less headspace in a keg vs about 40x the headspace in a bottle, where liquid (beer) is denser than gas (headspace), so the same amount of priming sugar, when kegging, promotes higher pressure therefore a higher level of carbonation. Probably more noticeable with relatively low carbonated beers like some English ales.

 

[McMullan]

My oh! my aren’t we sensitive when someone dares to disagree with you!
There are , in fact, some very good reasons to reduce the fermentable that you use when keg conditioning that result in better results. First, the amount of dissolved CO2 in 5 gallons of beer (keg) is higher than in a 12 oz bottle. This will be absorbed once the beer is chilled. Secondly, you are better able to prevent over carbonation and once you chill the keg and hook it up you are much less likely to have a foam (or bottle) bomb on your hands. I personally find that the overall mouthfeel is superior to force carbing at 15+lbs and again much less risk of over carbonation.
It’s not biology, but there’s definitely some physics involved!
Salut!

The dissolved CO2 level, before carbonating, is determined by yeast and fermentation temperature. So a bit of biology and physics involved, but a comparable fermented beer transferred to a keg is going to have the same level of dissolved CO2 as beer transferred to a bottle.

 

[Bassman2003]

I'm interested in learning how others keg condition with priming sugar, as opposed to force carbonating.

After conditioning, how long do you refrigerate before tapping?

Would tapping without refrigerating for long enough (a few days) potentially lead to a very foamy beer?

This is complex as it involves variables like amount of gas created and the ambient temperature of the keg.

The amount of gas created is based upon how much yeast activity you have to work with and how much sugar you add. If you add "X" amount of sugar and close the keg but your beer is not finished fermenting, you will end up with more gas created than expected. Which will lead to overcarbonation.

If you tried to serve at the warmer ambient temperature, you will be serving at higher pressures. If you look at a carbonation chart, a certain volume of CO2 is related to a certain pressure at a certain temperature. So lets say 2.6 volumes of CO2 at 45F is 16 P.S.I. That same 2.6 volumes of CO2 at 60F is 25 P.S.I. So this requires a lot more line resistance to properly pour a beer without the CO2 coming out of solution and foaming etc...

I would say making or buying a spunding valve is essential in order to work with natural carbonation. This allows you the one and only method to 'steer' an otherwise closed vessel. In the above overcarbonated example, you could put a spunding valve on and set it to your desired level of CO2 and the excess would blow off. Leaving only what you want when you put on the fridge.

Mac has a good approach of leaving the primed keg out at ambient temps for long enough to let all yeast activity finish. Then moving to colder temps for settling and then serving. Remember, you are really directing yeast activity when you naturally carbonate. They like warmer temps and do not like sudden drops in temperature.

Another option is true spunding which involves transferring the beer to the keg 3-5 gravity points before it is finished fermenting. This uses the last bit of fermentation to create the carbonation and with a closed transfer, ends up virtually oxygen free.

 

[mac_1103]

I’ve always assumed it was associated with less headspace in a keg vs about 40x the headspace in a bottle

I'm not sure where you're getting 40x from. Of course it will vary a bit depending on exactly how one fills each vessel, but I think the ratio of liquid to headspace with 5 gallons of beer in a corny vs 12 ounces of beer in a longneck is within a factor of 2 (edit - or 3).

 

[Closet Fermenter]

I dissolved 5 oz. of sugar in heated water and injected it into my keg after a closed transfer from the fermenter. The keg has been sitting in the closet for 3-½ weeks at +\-65°. The gauge has been steady fixed at this position for about a week.
I will now move it to the storage room outside my carport where my keezer is located. The temperature out there this time of year stays 45-50°. Heat generated by the three small freezers and the hot water heater only needs supplemental heating with a tiny space heater when temperatures dip into the sub freezing range for several consecutive days. It will sit there until I have space in the keezer. Since I adopted this procedure, I have served several kegs directly from the keg without refrigeration. I can let the temperature drop in there to the mid-forties by cracking open a window part of the day and reducing additional heating. This is a good temperature for my stout. It’s nice to have additional room in the keezer for an Altbier to age and have kegs in use just sitting around.

I will confess, this keg was was half of a 10 gallon batch. It’s brother keg was called into service before it reached full carbonation. It’s no issue (for me) just to put it in the keezer and hook up the CO2. Even with the shortened schedule, it was adequately carbonated so that I only had to apply serving pressure. Tasted fine.

One thing I have learned to do, and I am curious to hear from others, is that I find it necessary to pull the prv before hooking up to serving pressure. As you can see below, it gets fairly well pressurized at ambient temperature. I have not bothered to check pressure after chilling; I know that it will be less, but it is too easy just to pull the release and hook up the gas. I equate this to popping the top on a bottle.

Anyone have a carb chart that includes temperatures above 65°?

 

[Bassman2003]

I have yet to see a chart above 65F. I would guess you are sitting at about 2-2.5 volumes of CO2 with this beer. You could leave the spunding valve on when you put the keg in the fridge to see where it adjusts to. Then bleed some off through the valve which would be better from an oxygen point of view than pulling the PRV. I try to not to open anything directly on the keg as any opening is a potential oxygen entrance. Some distance away gives a tiny bit of buffer and the valve is designed for this.

 

[redrocker652002]

OK, so I am going to throw myself under the bus and say I have not read all the posts in the thread, but do have a question (albeit a pretty stupid one). So, if I were to add say 4oz of corn sugar to my keg at transfer from the bucket, leave it sit for say a week or two at room temp, throw it in my kegerator for another week and serve I don't need to use a CO2 bottle at all? Now, if this is correct I am pretty stoked as the last switch out cost me about 50 or 60 bucks for the CO2. If I can get away with even using cane sugar that is more a plus. Going to try and follow this one as this could not only save me a few bucks, but could allow me to have a few kegs on hand when one runs dry. Cool.

 

[mac_1103]

So, if I were to add say 4oz of corn sugar to my keg at transfer from the bucket, leave it sit for say a week or two at room temp, throw it in my kegerator for another week and serve I don't need to use a CO2 bottle at all?

Maybe for a couple of pours. But you will eventually need to hook up CO2 to maintain serving pressure. When you remove a pint of beer you have to replace it with a pint of gas or it will eventually a) stop flowing and b) lose carbonation.

 

[Bassman2003]

Yes, you will still need to hook the CO2 up but you will use a lot less over the course of the keg. The reason is - if you did not hook the keg up, the carbonation would gradually be sucked out of the beer with each draw. So you are replacing the liquid in the keg with tank CO2 to keep equilibrium.

 

[redrocker652002]

Maybe for a couple of pours. But you will eventually need to hook up CO2 to maintain serving pressure. When you remove a pint of beer you have to replace it with a pint of gas or it will eventually a) stop flowing and b) lose carbonation.

Got it. So the savings, so to speak, is that less gas to use to actually do the carbonation of the beer and only using the CO2 to push the beer out of the keg? This is all pretty cool.

 

[redrocker652002]

Yes, you will still need to hook the CO2 up but you will use a lot less over the course of the keg. The reason is - if you did not hook the keg up, the carbonation would gradually be sucked out of the beer with each draw. So you are replacing the liquid in the keg with tank CO2 to keep equilibrium.

Awesome. This sounds like a cool "might try" on my next keg.

So, in retrospect, I boil up some water and add the correct amount of corn sugar, say 4oz to the keg. Let it cool a bit and then do my normal transfer. Hit it with some CO2 to set the lid and let it sit for a couple of weeks at room temp. Then, in the kegerator and hook up the CO2 line and chill to serving temp and let it sit for another week? Am I in the right area here?

 

[mac_1103]

So, in retrospect, I boil up some water and add the correct amount of corn sugar, say 4oz to the keg. Let it cool a bit and then do my normal transfer. Hit it with some CO2 to set the lid and let it sit for a couple of weeks at room temp. Then, in the kegerator and hook up the CO2 line and chill to serving temp and let it sit for another week? Am I in the right area here?

Better to add the priming sugar to a purged keg and do a closed transfer. Or add the priming sugar to a sanitized keg at the start of fermentation and hook it up to purge with fermentation gas.

 

[Closet Fermenter]

Better to add the priming sugar to a purged keg and do a closed transfer. Or add the priming sugar to a sanitized keg at the start of fermentation and hook it up to purge with fermentation gas.

Yes, definitely. I inject the boiled sugar/water into a fermentation purged keg through the gas post with a large syringe, right after a closed transfer. Per recommendation here, I am going to start adding Ascorbic acid into the mix as well.

If employing this method, you might want to relieve the keg pressure and keep your hands on the syringe plunger when you connect to the gas post. Consider a moment; get that mental picture in your head, and you’ll know why I needed a mop, shower, and change of clothes!

 

[Closet Fermenter]

Got it. So the savings, so to speak, is that less gas to use to actually do the carbonation of the beer and only using the CO2 to push the beer out of the keg? This is all pretty cool.

I typically find my initial pressure a little higher than serving pressure, but by using a PT 2.0, I can “harvest” this extra CO2 and dispense a fair number of pours before connecting to the tank. I will admit that I may not be as particular about carbonation levels as some might be; I am ok within a range, so your preferences will determine how much you may pour before you feel the need to connect to the tank.
I will say, my tank has lasted a LOT longer after purging with fermentation gas, keg-carbing with sugar, and dispensing with the carbonation pressure.

 

[DuncB]

Anyone have a carb chart that includes temperatures above 65°?

Try this
https://brewingcalculators.com/forced-carbonation/

 

[doug293cz]

I’ve always assumed it was associated with less headspace in a keg vs about 40x the headspace in a bottle, where liquid (beer) is denser than gas (headspace), so the same amount of priming sugar, when kegging, promotes higher pressure therefore a higher level of carbonation. Probably more noticeable with relatively low carbonated beers like some English ales.

I have measured the headspace in a normally filled 12 oz bottle and a ball lock corny keg. In both the headspace was about 6% of the beer volume. So, headspace difference does not explain why there should be a difference in priming requirement.

Brew on

 

[doug293cz]

Half the amount of sugar works fine for me when kegging, but I think because I keg in under 10days the beer might still not be all the way to TG. Think I seen @doug293cz post that it only takes a gravity point of extra attenuation to cause trouble.

I am also quite surprised at the amount of CO2 in my beer on transfer sometimes, makes me wonder if the CO2 has not yet fully came to equilibrium so I have more volumes than the temp chart suggest.

If you keg before fermentation is finished, then the continuing fermentation will add carbonation to the beer. In this case less priming sugar would be required to reach a particular level of carbonation.

Yes, it does take some time after completion of fermentation for the CO2 in the beer to equilibrate with the headspace CO2 partial pressure (14.7 psi for a leak-free airlocked fermenter.) So, kegging before equilibration will have beer with a higher level of carbonation, and again less priming would be required. I have never seen any data on just how long equilibration takes, so trying to come up with a fudge factor for this effect is a difficult problem.

I don't remember making a post about 1 gravity point, but I've made a lot of posts, and don't remember them all. Might do some calculations if I get bored.

Brew on

 

[Closet Fermenter]

I have a theory. The reason folks got the notion that they needed to reduce the sugar when carbing a keg comes from their experience with dispensing those first couple pours. The pressure can be a bit over your typical dispensing pressure and you might get a bit of foam. I would suggest that if a bottle had a valve on the bottom that you opened to fill your glass, (without popping the cap), you would get a similar result! You could approximate this by turning a bottle upside down over a glass and popping the cap, but I bet we all can anticipate what that would look like without having to actually try it.
So, I think folks just started adjusting the sugar downward in the keg to reduce initial pressure, but were perhaps sacrificing full carbonation, which ends up being completed after tank connection.
This is the reason I referred to pulling the prv as “popping the cap”, then connecting to dispensing pressure.

This is only my guess. Others may have a better understanding or better theory; I am open to either.

 

[McMullan]

I have measured the headspace in a normally filled 12 oz bottle and a ball lock corny keg. In both the headspace was about 6% of the beer volume. So, headspace difference does not explain why there should be a difference in priming requirement.

Brew on

But if we bulk prime a batch then fill about 40 bottles, is the combined volume of headspace left in the bottles greater than the 6% headspace left in the keg?

 

[ba-brewer]

I don't remember making a post about 1 gravity point, but I've made a lot of posts, and don't remember them all. Might do some calculations if I get bored.

It is toward the end of one the other long keg sugar threads, I will look to see if I can find it.

I appreciate the time and effort you put into the calculations so thanks. I am sure your math is correct and to many people it holds true to use the same amount of sugar for kegging as bottling. I would say anyone starting out and doing their first primed keg start with half the amount and adjust as it is easier to add more carbonation then it is to remove extra.

edit: this is the postCarbing a keg with corn sugar

 

[doug293cz]

But if we bulk prime a batch then fill about 40 bottles, is the combined volume of headspace left in the bottles greater than the 6% headspace left in the keg?

No.

But my measurement was for 5.0 gal of beer (determined by weight) in a ball lock keg. If you put more or less than 5 gal in the keg, then the headspace volume to beer volume ratio changes. However, since you have roughly the same concentration (in g/L) in the beer and headspace at serving temp, you should use the same amount of priming sugar per keg independent of the actual volume of beer in the keg (you have to "carbonate" the headspace as well as the beer.)

Brew on

 

[Closet Fermenter]

If you keg before fermentation is finished, then the continuing fermentation will add carbonation to the beer. In this case less priming sugar would be required to reach a particular level of carbonation.

This makes a lot of sense. I have never (intentionally) tried to keg before full fermentation has ceased, so I’m starting from essentially flat beer when I prime in the keg, hence I need the full dose of sugar. My current rig doesn’t permit pressurized fermentation, but I just picked up a used ½ barrel sanke that I hope to move in that direction.
All good stuff here!

 

[doug293cz]

This makes a lot of sense. I have never (intentionally) tried to keg before full fermentation has ceased, so I’m starting from essentially flat beer when I prime in the keg, hence I need the full dose of sugar. My current rig doesn’t permit pressurized fermentation, but I just picked up a used ½ barrel sanke that I hope to move in that direction.
All good stuff here!

Beer at the end of carbonation is not totally "flat" as it has a significant level of dissolved CO2. For example an ale fermented at 65°F in an airlocked fermenter (CO2 partial pressure = 14.7 psi), the carbonation level is 0.88 volumes. So to carbonate to 2.5 volumes, you prime with enough sugar to create 1.6 volumes.

If you fermented in an open fermenter (CO2 partial pressure = ~0), then the beer would be truly flat at the end of fermentation.

Brew on

 

[Bassman2003]

Awesome. This sounds like a cool "might try" on my next keg.

So, in retrospect, I boil up some water and add the correct amount of corn sugar, say 4oz to the keg. Let it cool a bit and then do my normal transfer. Hit it with some CO2 to set the lid and let it sit for a couple of weeks at room temp. Then, in the kegerator and hook up the CO2 line and chill to serving temp and let it sit for another week? Am I in the right area here?

Close. You would want to move it to the kegerator, let it sit for a week, then hook the CO2 up and serve. Now I have thrown a curve ball at you because to accomplish this, you would need the carbonation level in the keg to match the PSI setting of the tank gas right? That is where a spunding valve comes into play. When you put the keg in the kegerator, you would put a spunding valve on the gas post after a few days (after temps lower) and set it to the same PSI as the tank gas. Now when you hook the gas up for serving, the lines should be be balanced.

 

[DuncB]

But if we bulk prime a batch then fill about 40 bottles, is the combined volume of headspace left in the bottles greater than the 6% headspace left in the keg?

Don't think so as it's percentage by volume so it should scale up.
However I'd be interested in the surface to volume ratio for the two situations.
Maybe that has a part to play?

 

[doug293cz]

Don't think so as it's percentage by volume so it should scale up.
However I'd be interested in the surface to volume ratio for the two situations.
Maybe that has a part to play?

Surface area to volume ratio is only a factor in the rate of CO2 absorption when force carbonating, and is not a factor in the equilibrium state. When naturally carbonating, the CO2 is generated in the bulk of the beer, and surface area to volume ratio will affect the rate of CO2 "escaping" from the beer into the headspace.

Brew on

 

[DuncB]

Surface area to volume ratio is only a factor in the rate of CO2 absorption when force carbonating, and is not a factor in the equilibrium state. When naturally carbonating, the CO2 is generated in the bulk of the beer, and surface area to volume ratio will affect the rate of CO2 "escaping" from the beer into the headspace.

Brew on

But you did do some work on volume of headspace, spunding carbonation and cold crashing effects.