Proper carb stone use - Ss Unitank

[abrewer12345]

hi all-
we threw our first batch into our unitank last night! we’re not going to ferment under pressure this round, but would like to use the carb stone to carbonate the beer at the end of fermentation. what psi do you folks usually use, and how long? 5.5 gallon beer in 7 gallon unitank. appreciate any help- cheers!

 

[Jtvann]

Need to cold crash first. Then check a temp chart. It works the same as kegging. You need to be able to trust your pressure gauge reading. If you are kegging after the unitank, not a big deal, you can come in barely on the side of undercarbonated. Your kegs will take care of the rest. When bottling direct, I'd say come in barely over carbonated for any losses in the system.

For specific numbers, at 40 degrees I go to 12 psi when kegging or 14 psi when bottling. Temp chart guides you.

 

[CodeSection]

@ronniescouten, don't forget to determine the carb stone's wetting pressure. The wetting pressure is the amount of pressure it takes before gas can move through the carb stone. According to SSB, their .5 micron carb stone's wetting pressure is in the range of 2-5psi. You can determine and test this by placing your carb stone in a jar of water and slowly increasing pressure.

Once you know what the stone's wetting pressure is, you must add the wetting pressure to the pressure you are carbing to on the carb chart. If you fail to do this, you will definitely under carb.

As an example, say your wetting pressure is 4psi, you cold crashed to 33F, and want ~2.5 CO2. The carb chart indicates at 33F @ 2.51 CO2 to use 9psi. So, you would add the carb stone's wetting pressure of 4psi to the 9psi. Thus, you would set the regulator at 13psi.

Individuals carb depending on style, recipe and personal preferences. I found most of my family, friends and clients like ~2.5 CO2 level.

 

[Rob2010SS]

Just to clarify something here....

Going to use the carb stone for the first time on my unitank. If the wetting pressure of the carb stone is 4 psi and I would typically want 10 PSI @ 35*F, I'd go t 14 PSI. That's easy.

So the CO2 regulator will say 14 PSI.

Will the pressure gauge on the tank read only 10?
Will the pressure gauge on the tank instantly read that or will it take time to build up in the tank since it's coming out of the carb stone?

 

[Vale71]

Will the pressure gauge on the tank read only 10?
Will the pressure gauge on the tank instantly read that or will it take time to build up in the tank since it's coming out of the carb stone?

Yep and no respectively. If most of the CO2 is being absorbed by the beer (which is what you should aim for) then headspace pressure should rise much more slowly. To maximize this you should not set 14 PSI right away but start with a lowe pressure (say 8 PSI) and slowly raise it in smaller increments.

 

[Rob2010SS]

Hmmm, ok.

Is there any harm in setting it right at 14 PSI right away? I get that some of that will not be absorbed by the beer, but other than possibly wasting CO2, any harm done?

As this was the first time using the carb stone, I learned a few lessons, this being one of them. I did set the regulator to 14 PSI and go right away. Gauge on the tank was reading 10 PSI after about an hour. Definitely a slow creep up.

Also, how long does it take to carb using a carb stone?

 

[Brooothru]

Yep and no respectively. If most of the CO2 is being absorbed by the beer (which is what you should aim for) then headspace pressure should rise much more slowly. To maximize this you should not set 14 PSI right away but start with a lowe pressure (say 8 PSI) and slowly raise it in smaller increments.

Curious if this process would be good for spunding as well, or if it's really necessary since the pressure build up is gradual when spunding. My usual process has been to set the release point at 1 atm (~15 psi) at normal fermentation temperature. Then when fermentation is complete and I cold crash, the tank pressure drops to around 12 psig. Lately my beers have seemed over-carbed, at least the ales but not the lagers. Could it be that I'm mistakenly setting the head pressure instead of a desired carb volume pressure for my serving temperature?

Brooo Brother

 

[Vale71]

Spunding is different in that the beer first has to reach saturation and then the excess CO2 diffuses into the headspace. As carbonation increases it increases first in the beer and then propagates to the headspace.
What you are observing when dropping the temperature after fermentation is a different issue and is due to having significant headspace in the fermentation vessel, as opposed to the negligible headspace in a bottle or the still much less significant headspace in a full keg. When you drop the temperature pressure decreases proportionately to the ratio of the starting temperature over the final temperature (absolute temperature, so degrees Kelvin) but the CO2 content of the beer does not change just because of the temperature variation. The solubility of CO2 will however increase so that to reach a new equilibrium some of the excess CO2 will have to migrate from the headspace to the beer until a new equilibrium is reached for the current temperature.
It's possible to calculate this analytically based on the starting and target temperatures and the headspace to liquid ratio but the important thing to know is that an increase in carbonation will always occur and it will be greater the larger the temperature difference and the higher the headspace to liquid volume ratio. To avoid that you need to look up the new equilibrium pressure corresponding to the target temperature and as soon as it's reached you should set the spunding valve to the updated target pressure to release the excess CO2.

 

[Vale71]

Hmmm, ok.

Is there any harm in setting it right at 14 PSI right away? I get that some of that will not be absorbed by the beer, but other than possibly wasting CO2, any harm done?

As this was the first time using the carb stone, I learned a few lessons, this being one of them. I did set the regulator to 14 PSI and go right away. Gauge on the tank was reading 10 PSI after about an hour. Definitely a slow creep up.

Also, how long does it take to carb using a carb stone?

You'll never waste CO2 while force carbing as the vessel is a closed system as long as you don't cause it to vent by exceeding the PRV's or the spunding valve's set pressures. This could however slow down the process significantly by causing some of the CO2 to bubble to the surface thus causing the pressure in the headspace to rise much faster. As soon as you reach target pressure in the headspace the process becomes almost identical to simple set-and-forget carbonation as your carb stone will not release more CO2 until some CO2 is re-absorbed from the headspace causing pressure to drop.
To get the highest possible CO2 absorbtion rate you should ideally always push just enough CO2 into the beer that the bubbles get completely absorbed by the beer without breaking the surface, which is generally not really achievable with our systems. Increasing the pressure in small increments can approximate the ideal process, will however require more involvement from the brewer.
As to how long it takes it really depends on how efficiently you can get the beer to absorb the CO2, which depends on bubble size (the smaller the better), temperature (the higher the temperature the faster CO2 is absorbed and not the other way around) and of course the amount of beer and the required CO2 increase.

 

[Rob2010SS]

You'll never waste CO2 while force carbing as the vessel is a closed system as long as you don't cause it to vent by exceeding the PRV's or the spunding valve's set pressures. This could however slow down the process significantly by causing some of the CO2 to bubble to the surface thus causing the pressure in the headspace to rise much faster. As soon as you reach target pressure in the headspace the process becomes almost identical to simple set-and-forget carbonation as your carb stone will not release more CO2 until some CO2 is re-absorbed from the headspace causing pressure to drop.
To get the highest possible CO2 absorbtion rate you should ideally always push just enough CO2 into the beer that the bubbles get completely absorbed by the beer without breaking the surface, which is generally not really achievable with our systems. Increasing the pressure in small increments can approximate the ideal process, will however require more involvement from the brewer.
As to how long it takes it really depends on how efficiently you can get the beer to absorb the CO2, which depends on bubble size (the smaller the better), temperature (the higher the temperature the faster CO2 is absorbed and not the other way around) and of course the amount of beer and the required CO2 increase.

Ok.... damn. Would there be any benefit to dropping the headspace pressure (either by venting the tank or by closing the CO2 tank) and kind of restarting the carb stone use? I was really hoping it would be carbed quickly...

 

[Vale71]

Shutting off the CO2 would be pointless at this point. You could vent the headspace to cause some more CO2 to be pushed in but you run the risk of not knowing when equilibrium has been reached and thus keep venting CO2 even after carbonation has been reached.

 

[Rob2010SS]

Shutting off the CO2 would be pointless at this point. You could vent the headspace to cause some more CO2 to be pushed in but you run the risk of not knowing when equilibrium has been reached and thus keep venting CO2 even after carbonation has been reached.

And just to make sure I"m understanding your point here, the problem here is that you'd then just be wasting CO2, right? There's still no risk of overcarbonating as long as your pressures aren't increasing, correct?

 

[Vale71]

Yes and possibly some beer aromatics might get stripped along with the gas.
If I were you I'd vent once down to 5 PSI and then do no more and wait for as long as you can before serving. Just how quickly do you need it carbed?

 

[Rob2010SS]

So, I HAVE to keg tomorrow sometime. I need the fermenter for a brew on Sunday. Ideally, I'd like to be able to serve it Monday as I have some people bringing howlers to fill, but that's not absolutely necessary. They'd perfectly understand if I have to wait an extra day or two to finish carbing in the kegs before filling their howlers. Friday is my absolute deadline for serving the beer at a party.

 

[Vale71]

Monday might be a bit tight but I would try and vent once and then leave the CO2 attached until you absolutely have to keg.

 

[Rob2010SS]

Curiosity, would my BEST option, for the sake of the quality of the beer and the aromatics, be to just leave it and keg as is and let it finish carbing in the kegs? Or will one way or another not make much difference?

 

[Vale71]

For quality not venting will certainly be better.

 

[Rob2010SS]

Probably what I'll do then. I don't want to affect the quality in any way. I can get it in kegs and finish carbing there if need be.

 

[Advance]

This post should be of use to you next time you carbonate using the carb stone:

https://www.homebrewtalk.com/threads/carbonation-help.680106/post-8885395

As for your current situation, It is hard to determine what level of aromatics you have knocked out of solution using the carbstone in the way you did. It is also hard to determine just what level of carbonation you have reached, because not all of the CO2 that was sent through the stone was absorbed into solution. If you wish to obtain the best possible quality for this batch you should leave the beer in the unitank and allow it to reach saturation equilibrium. During this time the excess pressure in the headspace will be absorbed into solution along with some of the aromatics you might have kicked out. To accomplish this simply leave your CO2 hooked up to the carb stone with the valve opened, at the regulator setting you initially set. I would give it 4-6 days before you make any adjustments to the regulator to reach your target carbonation level. When you do make the adjustments, make them very small (1/12 of a turn of the regulator every 30 mins or so). This would obviously require you to cancel your upcoming planned brewday along with your planned unveiling.

Another thing your should take into consideration is whether your kegging procedure would maintain the level of quality you have achieved upstream in your brewing process. If you are not liquid purging your kegs, then counter pressure filling them from the unitank, whatever quality you might have regained by leaving the beer in the unitank will more than likely be lost again.

 

[Rob2010SS]

This post should be of use to you next time you carbonate using the carb stone:

https://www.homebrewtalk.com/threads/carbonation-help.680106/post-8885395

As for your current situation, It is hard to determine what level of aromatics you have knocked out of solution using the carbstone in the way you did. It is also hard to determine just what level of carbonation you have reached, because not all of the CO2 that was sent through the stone was absorbed into solution. If you wish to obtain the best possible quality for this batch you should leave the beer in the unitank and allow it to reach saturation equilibrium. During this time the excess pressure in the headspace will be absorbed into solution along with some of the aromatics you might have kicked out. To accomplish this simply leave your CO2 hooked up to the carb stone with the valve opened, at the regulator setting you initially set. I would give it 4-6 days before you make any adjustments to the regulator to reach your target carbonation level. When you do make the adjustments, make them very small (1/12 of a turn of the regulator every 30 mins or so). This would obviously require you to cancel your upcoming planned brewday along with your planned unveiling.

Another thing your should take into consideration is whether your kegging procedure would maintain the level of quality you have achieved upstream in your brewing process. If you are not liquid purging your kegs, then counter pressure filling them from the unitank, whatever quality you might have regained by leaving the beer in the unitank will more than likely be lost again.

Unfortunately, I already have the grains milled and I can't brew next weekend so not brewing this weekend isn't an option, unless I want to toss the grains. I didn't like having to mill them that early in the first place, letting them sit another 2 weeks milled isn't an option in my head.

When I keg, I do counter pressure fill to kegs that have been 100% liquid purged with CO2. It is store bought CO2 and not naturally produced CO2, so I know that's a disadvantage slightly but good enough for how fast we go through kegs, I think.

So, I would like to clarify something quickly. Here's how it went down last night.

I hooked up the CO2 tank to the carb stone with the regulator set to 12 PSI, underestimating the wetting pressure at 2 PSI. After about 30-40 min, the tank head pressure reached 8 PSI and it stayed there, which showed me that the wetting pressure is at 4 PSI. So about 20 min later, I slowly increased the pressure on the regulator another 2 PSI and by the time I went to bed, I checked again and head pressure in the tank was at 10 PSI. So all of this over the course of maybe.... 2 hours.

While I'm not doubting that I may have pushed some aromatics out, is my situation really that bad or is it NOT that bad, just not ideal?

**EDIT** And thanks for the link, that is helpful. I just hope I didn't damage the beer aromatics too bad by what happened. I did a QUICK read on the carb stone use and thought I understood it. After doing it last night, thought it might have been too easy to be true!

 

[Advance]

I would say your situation is still good, just not ideal. Its not like you introduced large amounts of oxygen to the fermenter or something. Given your current situation with the milled grains, I would go ahead and transfer the beer to a keg and finish carbonating in the keg to free up the fermenter. Just mark it up as one of the many mistakes we all make on the road to trying to perfect our individual brewing processes. In the future, when making adjustments to the regulator during the carbonation process you should not be using the pressure gauge on the regulator. The small incremental adjustments will not even present themselves on the pressure gauge at the time you make them. Use the change in position of the adjustment knob instead.

 

[Rob2010SS]

I would say your situation is still good, just not ideal. Its not like you introduced large amounts of oxygen to the fermenter or something. Given your current situation with the milled grains, I would go ahead and transfer the beer to a keg and finish carbonating in the keg to free up the fermenter. Just mark it up as one of the many mistakes we all make on the road to trying to perfect our individual brewing processes. In the future, when making adjustments to the regulator during the carbonation process you should not be using the pressure gauge on the regulator. The small incremental adjustments will not even present themselves on the pressure gauge at the time you make them. Use the change in position of the adjustment knob instead.

Thanks man. Appreciate the advice! Definitely putting this one in the "vault" so I don't make this mistake again.

 

[Brooothru]

Spunding is different in that the beer first has to reach saturation and then the excess CO2 diffuses into the headspace. As carbonation increases it increases first in the beer and then propagates to the headspace.
What you are observing when dropping the temperature after fermentation is a different issue and is due to having significant headspace in the fermentation vessel, as opposed to the negligible headspace in a bottle or the still much less significant headspace in a full keg. When you drop the temperature pressure decreases proportionately to the ratio of the starting temperature over the final temperature (absolute temperature, so degrees Kelvin) but the CO2 content of the beer does not change just because of the temperature variation. The solubility of CO2 will however increase so that to reach a new equilibrium some of the excess CO2 will have to migrate from the headspace to the beer until a new equilibrium is reached for the current temperature.
It's possible to calculate this analytically based on the starting and target temperatures and the headspace to liquid ratio but the important thing to know is that an increase in carbonation will always occur and it will be greater the larger the temperature difference and the higher the headspace to liquid volume ratio. To avoid that you need to look up the new equilibrium pressure corresponding to the target temperature and as soon as it's reached you should set the spunding valve to the updated target pressure to release the excess CO2.

OK. Now this is starting to make sense. The first issue at hand would appear to be an accurate measure of actual beer volume in the fermenter and subtracting that from an accurate known volume of the fermenter itself. The second variable I can calculate, but the actual amount of beer varies with each batch. Absent an accurate indication of level I'll be guessing at best of the ratio of volumes. At least now I can understand why my beers have been off with regards to carb levels since I started spunding. Thanks for the good explanation.

Brooo Brother