Adding Yeast to Korny Keg for Natural Carbonation

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Gee Tee

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I've never kegged before but would like to add yeast for natural carbonation. Do I need to cut some of the bottom of the metal tube so the sediment doesn't come out? If so, how much?
 
I've never kegged before but would like to add yeast for natural carbonation. Do I need to cut some of the bottom of the metal tube so the sediment doesn't come out? If so, how much?
You really shouldn't need to add yeast unless it's a very high ABV beer or has been bulk aged for a long time. You can cut the dip tube if you want. How much depends on how clear the beer is when it goes into the keg more than on whether you carbonate naturally or with bottled CO2. Or use a floating dip tube. Or just toss the first couple of yeasty pours.
 
I'd rather carbonate naturally (it also saves on CO2 so it'll last longer). I have to add yeast tfor it to carbonate naturally, no?
 
I have to add yeast tfor it to carbonate naturally, no?
Usually no. There is still plenty of yeast in your beer at the end of fermentation. Unless it's very high ABV or has been aging for a long time before you carbonate it. You do have to add sugar.

I do this all the time and I only add yeast under the circumstances mentioned.
 
There is almost always enough living yeast to carbonate in the keg (or bottle.) Add priming sugar, leave it for a couple of weeks at room temperature or very slightly warmer, and you should be good.

It’s possible you’ll get slightly more reliable results (i.e., faster carbonation) if you add a pack of CBC-1 or the like. And I would indeed add it if you’re looking at a particularly high gravity beer, or you cold crashed aggressively.

You probably don’t need a floating dip tube, but the FlotIt 2.0 is really a great product.
 
You don't need to add yeast to the keg, instead naturally carb by transferring the beer to the keg when it's approximately 4-5 gravity points from final gravity and then put a spunding valve on the keg to release any excess pressure. Do know what your actual final gravity is going to be, you will need to do a fast ferment test, where you take some of the wort, like 0.25 Liters from the fermenter after pitching yeast and put it in a jar with loose cover on it, swirl it now and then, and in a few days check the gravity. With this method, you would need to cut dip tube because you are transferring the beer before cold crashing, so will have a lot of trub in keg, then when it's done and you cold crash keg, transfer it to a serving keg. Or if you use a floating dip tube, you can serve from that keg.

Option 2 is treating the keg just like a bottle. Add priming sugar and let the beer carbonation in keg. Now this can be done after cold crash, so no need for cutting dip tube. But use a carbonation calculator as you need less priming sugar in the keg then you do in when bottling.
 
But use a carbonation calculator as you need less priming sugar in the keg then you do in when bottling
No you don't. Unless you want less carbonation. A keg is just a very large bottle. The biology, biochemistry and physics are all exactly the same. So why should we expect more CO2 from any given amount of sugar just because the beer is in a keg instead of a bottle?
 
I've never kegged before but would like to add yeast for natural carbonation. Do I need to cut some of the bottom of the metal tube so the sediment doesn't come out? If so, how much?
Since you are new to kegging, I would say it would be useful to explore the options before trying. Spunding is a great practice and it is easy. But you do need a way to track gravity points as you are transferring the beer towards the very end of fermentation. But it is oxygen free and reliable. And it is the traditional German way of brewing if that interests you.

It is more complicated to keep oxygen out when trying to add sugar or yeast to a keg after the fact. But can be done. Kegging and natural carbonation are all about zero oxygen imho.
 
No you don't. Unless you want less carbonation. A keg is just a very large bottle. The biology, biochemistry and physics are all exactly the same. So why should we expect more CO2 from any given amount of sugar just because the beer is in a keg instead of a bottle?

Weird, then BeerSmith's, which I use, carb tool must be wrong. It shows, for a 5 gallon batch at 2.5V in a 65 degree basement, that the keg would need 2.14 oz of corn sugar, while if bottling I would need 4.27 ounces of corn sugar.
 
Weird, then BeerSmith's, which I use, carb tool must be wrong
Yes it's wrong if you think about it. Yeast ferment each molecule of glucose into two molecules of ethanol and two molecules of CO2. The yeast don't know if they're in a bottle or a keg. But this is all over the internet and people swear that it works perfectly. Because if you add 2.14 oz to a keg at give it two weeks at ambient, and then put it in the kegerator at 10 PSI for another two weeks, you will have perfectly carbonated beer. But that's half natural carbonation and half forced carbonation.*

*edit - not that there's anything wrong with that
 
Weird, then BeerSmith's, which I use, carb tool must be wrong. It shows, for a 5 gallon batch at 2.5V in a 65 degree basement, that the keg would need 2.14 oz of corn sugar, while if bottling I would need 4.27 ounces of corn sugar.
4.27 oz. seems in the ballpark for 5 gallons. It's strange that, for practical purposes, 2.14 oz. is one-half.

Possible that 2.5 gallons batch size was entered by mistake?

I agree with @mac_1103, nothing wrong with under carbonating and finishing with bottled CO2.
 
4.27 oz. seems in the ballpark for 5 gallons. It's strange that, for practical purposes, 2.14 oz. is one-half.

Possible that 2.5 gallons batch size was entered by mistake?

I agree with @mac_1103, nothing wrong with under carbonating and finishing with bottled CO2.
Doing some research, it appears that headspace is the reason that the calculator shows less DME needed for a keg. One post on BeerSmith forums mentions that a keg full with 5 gallons of beer has approximately 10 ounces of headspace , which represents 1.57% of the total volume. Meanwhile, beer bottles, which are really 13 ounces that hold 12, have 1 ounce of headspace, but 5 gallons being 53 bottles, means a total of 53 ounces of headspace, thus the need for more sugar.
 
I think that @doug293cz did some maths on the headspace in a keg versus that in bottles and the surface areas relating to them both.
Surface area doesn't matter for the end result, only the headspace volume to liquid volume ratio will affect the final carbonation level. A standard 5 gal corny keg, and a 12 oz bottle with normal fill have about 6% of the liquid volume as headspace, so a corny is just like a big bottle. These headspace to liquid volume ratios were measured, not calculated.

Brew on :mug:
 
One post on BeerSmith forums mentions that a keg full with 5 gallons of beer has approximately 10 ounces of headspace , which represents 1.57% of the total volume.
Did they happen to say where they got that 10 ounce number? Did they explain how the smaller headspace volume allows the yeast to generate more CO2 from a given amount of sugar?
 
Thanks. But see the next post - his assumptions and arithmetic are off. For example:

"That means the headspace is about 96 in^3."

Volume in gallons is volume in cubic inches divided by 231. So 96 cubic inches is 0.416 gallons. 0.416*128=53.25 ounces, not 10.

"The beer is taking up the remaining 19.5 inches of height for a total of 1240 in^3."

1240 cubic inches is 5.38 gallons. 5 gallons is 1155 cubic inches.

edit - also, 96/(1240+96)=0.0719, not 0.0157; i.e., >7% not <2%

And see #15 above - Doug actually measured it. And like the other poster in that Beersmith thread, I'd still like to know how a 5% difference in total volume of the container would lead to a two-fold difference in carbonation level.

I prime in kegs all the time. Five ounces of corn sugar in five gallons of beer. 68F for two weeks. Haven't overcarbed yet.
 
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I prime in kegs all the time. Five ounces of corn sugar in five gallons of beer. 68F for two weeks. Haven't overcarbed yet.
Ditto! Also, when I ran out of corn sugar, I just used table sugar and couldn’t tell any difference other than the price.
Besides, overcarbing is not a difficult fix. Shake and vent as necessary, start pouring without connecting to the gas, or a combination of the this. It’s not a permanent condition. Cheers! 🍻
 
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Yes to the 10 ounce. See post #4...BeerSmith Forum
As pointed out above, I measured the headspace volume at 0.3 - 0.35 gal when exactly 5 gal of water is put in the keg. I measured the water by weight - 1 gal @ 68°F (20°C) weighs 8.33 lb, so 5 gal weighs 41.65 lb. The headspace volume is then determined by the weight of water required to fill to the rim of the keg. I did not check different kegs to do any characterization of variability among kegs.

The only thing plausible about the linked post is the speculation on a possible difference in how much CO2 is knocked out of the beer during transfer to bottles vs. kegs. I can't think of a way to test this hypothesis without being able to measure the amount of dissolved CO2 in beer. Also, any such effect would be widely variable depending on the details of the transfer.

Brew on :mug:
 
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