carbonation and head space

[jbryce]

I carbonate with a stone in a 7bbl grundy tank and typically have pretty good results at about 16 psi and 36 degrees. Recently my yields have improved and I have had less head space in the brite tank. I am pretty happy with the higher yields, which have been leaving only 10 gal or so of head space, but I can't get the beer to carbonate. this is true even when I jack the pressure way up. The only thing that works is pulling some beer out and trying again. Why does this happen?

[Larry Horwitz]

What method are you using to force carbonate?

do you vent as you pressurize, etc.

Give me some more info on your set-up and I (or someone else on this forum) can give you some pointers

Larry

[jbryce]

I only vent if I am in a hurry to get the beer carbonated(rarely)...otherwise the tank is sealed up and I let it pressurize overnight. when i arrive in the AM, it has reached full pressure and is carbonated. I know how to use carbonation charts for temp/pressure/etc, and it usually works fine, but I don't understand why a lack of head space would hinder carbonation.

[rudge75]

More headspace=faster carbonation
At least for us...

Here's what we do:
We use 8.3 hectoliter grundies for serving & conditioning.
We've only got one tank fitted with a carbonation stone for which we use a feed & bleed technique @ 15 psi @ 34f. for 1 hour. Usually, if our volume is 790 - 800 liters, this does the trick (2.3 vol. target). If we've got 800-820 liters it takes about another 15 minutes due to the larger volume/less surface area of the beer.

However for most of our beers, we're patient & we force carbonate using top pressure (28 psi) for approx. 5 days, after which we take a Zahm & Nagle reading. When full (820 Liters) it takes one more day to carbonate because less surface area is in contact than when we target 790 liters.

The most accurate way for us to measure the co2 in solution is with the Zahm & Nagle meter. Keep in mind that this device actually measures what's in solution, not what the headspace/temperature/pressure relationship is. The last brewery I worked at didn't have one. Supposedly we targeted 2.3 vol Co2 (we only read the headspace pressure/temperature relationship) but there's no way that beer was 2.3 vol. It didn't have the "prickle" I now associate with a beer in that range.

I'm guessing that you don't have a Zahm & Nagel Co2 meter. If you do have one, sorry for the assumption.

Love it or lump it, it's just my 2 cents:

Happy Brewing,
Dave Rudge
Head Brewer
Bushwakker Brewing Co.
http://www.bushwakker.com

[Chip Tate]

Your carbonation is taking longer because the speed at which the CO2 dissolves in the beer at any given pressure and temperature is going to be a function of the surface area of the beer and the amount of beer you're trying to carbonate. If your fermenter tappers towards the top, this would reduce the available surface area. Even if it doesn't, you've still got the same surface area (i.e. same rate at which CO2 is entering the beer), but more beer to carbonate--so it takes longer.

Longer carbonation times are not necessarily a problem. But if you need it carbonated faster, you'll have add more pressure, lower the temperature, or increase the surface area available for CO2 dissolution. In practice, you're best bet is probably going to be increasing the surface area by using a carbonation stone (maybe add one inline to the tank with a few tri-clamp fittings) and vent from the top of the fermenter. Every degree counts here, get that beer as cold as you can before transferring and carbonating it.

Good luck.

[jbryce]

Thanks for the advice, but I think that I need to do a better job of clearifying my problem...The problem is not that carbonation is taking longer, but that I can't get it to carbonate enough without taking what I think are drastic measures. To clearify, I am already using a stone. With the decreased head space I haven't been able to get a batch to carbonate enough without doing some combination of the following:
1. jack the pressure up ridiculously high (to a point that my brite tank (grundy) starts to leak CO2)
2. pull some beer out into kegs and then force carbonate the kegs, try again on the brite tank which now has less beer in it.
3. relieve pressure from the top of the brite tank to let it start blowing more CO2 through the stone again, repeat severeal times. (this seems to waste quite a lot of CO2)

It would seem to me that time has little to do with this problem...If I am setting the regulator to XX psi and let it carbonate over night...at some point during the night, probably within a few hours, the tank will reach XX psi and the carbonation level of the beer isn't going to change no matter how long I let it sit, because the regulator is set at XX psi...right?

I think that I can understand how before the carbonation level of the beer would reach a higher point if there were more head space, because more CO2 would have to be bubbled in to get the pressure to equalize the requlator setting with the increased head space.

So what is the easy way to do this, what is my best solution?

[MikeJordan]

I think you need to allow yourself more headspace. The following procedure works well as I have used it at several different breweries. I could usually carbonate a full tank in 1.5-2 hours.(depending on beer temp.) If your stone is sized on the large side (genetics??) then maybe only .75-1 hr. I always had 15-20% headspace in the bright beer tank. Carbonate through the stone at/or around 30 psi. Ideally the beer will be nice and cold (32-36F) so the beer will absorb the CO2 faster. Allow the tank pressure to rise up to 15 psi if your tank will handle this pressure. At this point bleed off excess pressure while still keeping 15 psi backpressure on the tank. If beer starts foaming out the blow-off arm/CIP arm then the tank is either too full or almost carbonated. I usually stop carbonating at this point, close off the pressure relief valve and allow the beer to sit for 10-15 min. Then check your volumes. If your low then additional time is needed. I've found 10 min. will generally give me .10 vol increase in CO2 measurement. If you're trying to capture some natural CO2 at the end of fermentation let me know. A great article was published last spring about pressurized fermentations. (New Brewer, Vol. 19, No.2) Hope this works for you.

[Chip Tate]

Correct me if I'm wrong, but it sounds like the stone you're talking about using is in the Grundy, right? If so, I was suggesting that in addition to using this stone for "top off" carbonation, that you use a stone in the transfer line from your fermenter to the bright tank. If you can get you beer icy cold and put this stone as far up stream as possible, it will take you a long way toward carbonating the beer before it's even in the tank.

As for your question about time and carbonation, the pressure in the tank itself should only take a matter of seconds, not hours, to reach your target pressure. What takes time is getting that head pressure to dissolve in your beer. The reason head space makes such a difference again has to do with the volume of beer. For example, say you have a surface area of 1 square yard where the beer meets the CO2. As long as that area stays the same along with the psi on the tank and the temperature, CO2 will go into your beer at a constant rate (say 100 grams/ hour for argument sake). Another way to think of volumes of CO2 is grams of dissolved CO2 per gallon beer. Obviously then if you wanted 10 grams of CO2 per gallon beer, that would take 1 hour to dissolve this much CO2 in 10 gallons. But if you double the amount of beer to 20 gallons and everything else stays the same, it will take twice as long to reach this same level. In practice, these carbonation levels are not right and the model is little too simplistic (i.e. steady state), but the principle holds true.

For fastest carbonation, I'd make sure to use an in-line stone far upstream as possible as cold as possible (a longer transfer hose can provide more mixing time) and then feed and bleed more CO2 as needed to top off. With a good stone, this should work regardless of how full your tank is. If you're in no hurry, keep the temp stable, set the pressure right and let it sit--no worries. It might take days to carbonate, but it's easy and foolproof and doesn't involve "drastic measures"--the carbonation will eventually get there for sure. Hope that helps a little.

[jbryce]

Chip,

Thanks!…That helped a lot, and yes the stone is in the Grundy. Which brings me to my next question…what’s the point of having a stone in the tank if it is the head pressure that is doing the work…isn’t the Co2 just coming out of the stone, up out of the beer and then becoming the head pressure? Does having the stone in the tank actually help, or is its contribution negligible? I will try to get a stone that can be used in-line or some other fittings, as the one in the tank is too big for the tee fitting that I have. Thanks for your help -John

[Chip Tate]

Chip,

Thanks!…That helped a lot, and yes the stone is in the Grundy. Which brings me to my next question…what’s the point of having a stone in the tank if it is the head pressure that is doing the work…isn’t the Co2 just coming out of the stone, up out of the beer and then becoming the head pressure? Does having the stone in the tank actually help, or is its contribution negligible? I will try to get a stone that can be used in-line or some other fittings, as the one in the tank is too big for the tee fitting that I have. Thanks for your help -John

John,

Glad to know I got your question right. The stone in the tank is actually good to have for several reasons. First, because you can force carbonate/ top up your carbonation more quickly by being able to sent CO2 in at the bottom of the tank and bleed it off at the top. As you mentioned, this does use more CO2 than some other options, but its good to have this option available. I would add that I don't really like to feed and bleed if I can help it because it can have a strong "scrubbing" effect on the beer and can purge a lot of hop aroma that I'd prefer to keep in the beer.

Second, even if you don't bleed CO2 from the top (ie just set your regulator at the right pressure routed through the stone and wait), the stone does speed the carbonation by dispersing the CO2 into the beer in tiny little bubbles that will rise through the beer. This greatly increases the surface area available for CO2 to dissolve into the beer and therefore speeds the carbonation. The bubbles of CO2 will actually be bigger using this method than if you were forcing a higher volume of CO2 through the stone (like in the feed and bleed method), but still a little faster than just applying head pressure. --Chip

[MikeJordan]

Chip,

I would like to comment on the "feed and bleed" method of carbonating. The theory of aroma being scrubbed from the beer makes logical sense. Personally I have never performed trials of different carbonation methods to compare products and their aroma side by side. I think it's very difficult to compare aroma between non-carbonated and carbonated product due to the fact that the CO2 is a carrier of aroma. I have carbonated beer in many different fashions (natural by bunging up FV near end of fermentation, bottle condition, carbonate during ruh transfer, pinpoint carbonation, and "feed and bleed") It seems I always have some "touching up" before packaging and usually use the "feed and bleed" method. When carbonating during beer transfer or using a pinpoint carbonator I have always had backpressure on the BBT. It's inevitable that pressure will have to be released off the BBT during filling and some hop aroma may be lost. I've never had the luxury of keeping beer in a BBT for extended amounts of time (over 48 hours) due to tank restrictions and time constraints. Therefore I cannot really comment on letting the beer sit and carbonate slowly. I guess I'm curious how much aroma is really lost during this process? I have always felt that if a beer didn't have enough aroma then I need to resolve the issue farther up the beerstream and use more hops. Yes, I'm a hophead!

[Chip Tate]

Mike,

I would generally agree with you. If the aroma is so delicate that a little scrubbing damages it, then other things besides carbonation method need to change. I don't think that the relatively minimal "touch up" feed and bleed carbonation that you're talking about is really a problem. I really only meant to point out that extensive feeding and bleeding can have a significant scrubbing effect and that this fact should be remembered in choosing a carbonation method. For example I would probably not choose to carbonate entirely flat Pilsner that had been heavily dry hopped with the feed and bleed method (top off the carbonation, yes, but not only use feed and bleed carbonation).

I'm glad you mentioned the option of naturally carbonating the beer. If you aren't going to filter, and have a good handle on the finer points of natural carbonation by priming with krausen beer or other primings, there are some real advantages to the natural method. The first is obvious: there's no waiting at all. Just add the right amount of priming and in the bottle/ keg it goes. The other benefit is even more important in my mind: oxygen uptake. By carbonating in the final package, you can get the yeast in solution to metabolize all of the oxygen that was added during packaging and much of the oxygen that migrates into the package over time (bottles). While this method is no replacement for good packaging practices, yeast in the package can significantly extend the shelf life of the beer and be SLIGHTLY more forgiving if a few bacteria get into the package. I'll repeat again though, I would never count on yeast's effect in the bottle to make up for poor sanitation or packaging procedure. Natural and artificial methods can also be combined to give the best of both (speed, ability to fob, and superior shelf life). -- Chip

[dick murton]

Carbonating by rousing extensively will wash out a large amount of aroma - certainly enough to be noticable - one of the reasons we do not do itexcept under extremis, and then only for our own products, not products brewed under licence.

Being a large brewery it is easy for us with expensive kit to carbonate on transfer from one vessel to another, injecting into the beer stream prior to a mixer, at high pressure. If you want to do something similar, but without the auto control, you could always calculate the amount of CO2 required to be dissolved, and weigh a gas bottle to determine the rate of injection, or more accurately when enough has been injected in total. Use a flow meter (rotameters are simple and adequate) to control the flow

The other points that no one has mentioned are (a) that over-rousing / purging can affect the head formation and retention, and may also lead to hazes and gushing in highly carbonated beers, due to particle formation by the proteins.

In other words, get it right pre filtration, and preferably by not rousing in tank. Bottle conditioning is great, but should still aim for a lvery ow oxygen in package to prevent beer oxidising before the yeast has mopped all the oxygen up.