Forced Carbonation Using a Carbonation Stone

[Nicegirl]

Since I began to home brew I have always been a big fan of forced carbonation and since I brew a lot of lagers it helps cut down on the time frame between brew day and the time which you can open one and enjoy the fruits of your labor.
I have tried the many methods described throughout the brewers forums; the shake, rattle & roll, injecting the gas through the liquid out line, carbonation stone, etc. Being a woman, shaking a keg with 5 gallons of beer in it is not an easy task and I have not had much luck with injecting the gas thorough the liquid out tube. Never seemed to produce the proper carbonation levels so I turned to a carbonation stone. That's where things got real confusing.
If you have ever researched the proper way to use a carbonation stone, there are more answers and different information out there than there are styles of beer with no real clear cut information, so I decided to do some real in depth research into this matter and wanted to share this information with those that have had the same experience.
The big problem I was having using a carbonation stone was under carbonation of my beer. I did exercise all of the normal procedures; making sure the beer was near freezing, getting the stone near the bottom of the keg, etc. and still had the same problem...under carbonated!
What I came to discover from my research is a thing know as "wetting pressure". This is the amount of CO2 pressure required for the carbonation stone to begin to emit CO2 gas.
What I came to find out is that my 0.5 micron stone has a wetting pressure of 4 P.S.I. All stone are different so YMMV. There is an easy way to determine the wetting pressure of your stone.

1. Attach your stone to your CO2 regulator.
2. Place your stone in a bucket of water.
3. Slowly turn up the pressure on your regulator until you start to see the stone emit a fine trail of bubbles.
4. Check the pressure setting on your regulator.

The pressure setting on your regulator is the "wetting pressure" of the stone. For mine it was 4 P.S.I. Make certain to add the "wetting pressure" factor to the recommended pressure setting in your carbonation chart, i.e.; 10.20 lbs. plus 4 equals a pressure setting of 14.20 lbs. on your regulator.
I begin the carbonation process by setting my regulator at 6 PSI (4 PSI wetting pressure plus 2 lbs.) and let the gas run for an hour at this setting. Now begin to adjust your regulator pressure by 2 PSI every 30 minutes until you reach the desired pressure setting plus your stone's wetting pressure. Leave your gas on for 48 hours and you will have a perfectly carbonated beer that is fully saturated with CO2 that won't give up the bubbles in the first 5 minutes in your glass
I also built an inexpensive "bleeder valve" device for checking the "head pressure" in the keg. As we know, Mother Nature will do her very best to equalize the pressure in a keg between the head space and the liquid beer so checking the head space pressure is a great way to measure the amount of CO2 in solution.
I'll pop the bleeder valve on the keg several time during the 48 hour carbonation period to check my head pressure. When the reading on the bleeder valve gauge matches the volume of CO2 pressure desired for your beer type...you're done.
Another thing that I found that helps is to refrigerate your keg prior to racking your beer into it. I normally place my keg next to my carboy in the refrigerator about 48 hours prior to racking. Helps maintain the cool temperature of the beer for carbonating purposes.
The DYI section of this forum describes how to build a "bleeder valve". If you can't locate this thread, send me a PM and I'll send you a parts list for making your own. Fairly inexpenseive and an invaluable tool for carbonation.
I have now successfully carbonated several batches using this method and no more under carbonation. Perfect every time!

 

[Woodbrews]

Great post. I share your experience with different methods of carbonation. My last batch, an APA, ended up perfect, but I think it was more a matter of luck than anything else. I have yet to settle on a reliable method of force carbonating. A couple of questions - how do you attach your carbonation stone? Do you sanitize the stone between batches, and if so, how? Thanks!

 

[Nicegirl]

Great post. I share your experience with different methods of carbonation. My last batch, an APA, ended up perfect, but I think it was more a matter of luck than anything else. I have yet to settle on a reliable method of force carbonating. A couple of questions - how do you attach your carbonation stone? Do you sanitize the stone between batches, and if so, how? Thanks!

Hi Woodbrews,
I use a carbonation lid on my kegs with the carb stone attached to a piece of vinyl tubing long enough to get the bottom of the stone about 1" from the bottom of the keg.
As far as sanitizing, I boil the stone in water for 20 minutes after every use and then hook it up to my CO2 system to blow out any remaining water in the stone before storing it for the next use.

 

[pfgonzo]

This was fascinating! Learn something new every day, thanks!

 

[BlkWater_brewer]

To go one step further. I simply use a short piece (1/2") of tubing attached to the stone and the gas post in my corny. Attach the gas line as usual and invert the keg and turn on the CO2. I have a few stones so I usually just leave it or you could simply pull it out when finished.

 

[ChapBrewer]

Carbonation stones are a really great way of carbonating a batch of beer correctly and quickly. I usually go from flat beer to ready to bottle or drink in a couple of hours for a 1/2 bbl keg. I like to leave it for another 24 - 48 hours to make sure it has reached equilibrium and the carbonation levels are correct, but it's usually just for piece of mind since it's always properly carbonated.

The process I used is borrowed from commercial microbreweries and it works really well:

1. Set the head pressure to 1 psi less that what your target pressure is, for instance, if your beer is at 35°F and your target pressure is 11 psi, set your head pressure to 10 psi.

2. Find a way to measure the head pressure, I use a dirty gauge but this can be a cheap and easy DIY project.... or get a dual regulator for your CO2 tank.

3. Find the wetting pressure of your carb stone and add all other pressures in the keg + 1 for the pressure the liquid usually creates. For instance, the wetting pressure of my stone is 4 psi + 10 psi head pressure + 1 psi liquid = 15 psi. THAT is the pressure at which the stone will begin bubbling.

4. Set it 1 psi higher than that (16 psi for this example) and leave the gas flow until it stops by itself, which means the liquid will be saturated with enough CO2 and it will reach equilibrium at 11 psi, then the gas will stop flowing to the beer.

Here's a picture of the keg with all its fittings, as you can see, I use a chest freezer + johnson controller for temp control. It's a sankey keg with some extras but there should be no problem doing something similar with a corny.

The setup can get a little pricey but it's worth it when you save 2-3 weeks every time you brew a batch.

p.s. Sorry for my bad english, it's not my native language

 

[bruhaha]

This was a very interesting post, nicegirl. I brew Pilsners as my go to brews, and did want to mention something you said in that forced carbing with carbonation stones reduces the time for grain to glass in a lager. My experiences are that a lager takes a good 8 weeks or more to fully mature and condition regardless of carbing, kegging or bottling. I rack to keg, apply 12 psi (as a rule) and let it ride until tap day.

None the less, your post was very technically interesting and thanks!

 

[Lauritsen]

I am gonna try using such stone and carbonate wine into sparkling wine....

any tried that?

 

[Jayf19]

I'll pop the bleeder valve on the keg several time during the 48 hour carbonation period to check my head pressure. When the reading on the bleeder valve gauge matches the volume of CO2 pressure desired for your beer type...you're done.
Another thing that I found that helps is to refrigerate your keg prior to racking your beer into it. I normally place my keg next to my carboy in the refrigerator about 48 hours prior to racking. Helps maintain the cool temperature of the beer for carbonating purposes.
The DYI section of this forum describes how to build a "bleeder valve". If you can't locate this thread, send me a PM and I'll send you a parts list for making your own. Fairly inexpenseive and an invaluable tool for carbonation.
I have now successfully carbonated several batches using this method and no more under carbonation. Perfect every time!

Not quite sure I understand this part? Is this only for sanke kegs or would something similar be needed on a cornelius keg?

 

[Qhrumphf]

Simple with a spunding valve. Get beer as cold as possible (30-32F ideally, 38F max). Pressurize keg to *above* your equilibrium pressure and set spunding valve accordingly. Apply gas in pressure through the stone above that (at least higher differential than wettting pressure of the stone). Carb to taste. Once carbed, drop keg pressure to equilibrium and you're done.

The closer to equilibrium and higher differential (and higher the temp) the faster it'll carb but more it'll foam. Higher overpressures, lower temps, and smaller differential will take longer but suppress the foam.

The drawback to this, constant blowoff will cause a slight reduction in aromatics. But that's outweighed by the gas sparging effect, where incoming CO2 will drive off other gasses, like dissovled oxygen picked up during the transfer.

You can also easily overcarb this way if you don't pay attention. And with a single keg and decent stone, this'll carb FAST.

 

[Jayf19]

Isn't it simpler to just progressively increase the PSI as the OP originally states :

I begin the carbonation process by setting my regulator at 6 PSI (4 PSI wetting pressure plus 2 lbs.) and let the gas run for an hour at this setting. Now begin to adjust your regulator pressure by 2 PSI every 30 minutes until you reach the desired pressure setting plus your stone's wetting pressure. Leave your gas on for 48 hours and you will have a perfectly carbonated beer that is fully saturated with CO2 that won't give up the bubbles in the first 5 minutes in your glass

I understand the point of determining the quantity of dissolved CO2 vs simply reading the head space pressure, but I don't really understand how a bleeder valve helps obtain such a reading.

 

[Qhrumphf]

Isn't it simpler to just progressively increase the PSI as the OP originally states :



I understand the point of determining the quantity of dissolved CO2 vs simply reading the head space pressure, but I don't really understand how a bleeder valve helps obtain such a reading.

Because my way a corney or sanke keg should be fully carbed in 20 or 30 mins with a decent stone. Likely less. The bleeder valve lets you blast in significant amounts of gas while not overpressurizing your vessel. Plus I've seen routinely a 30% or more reduction in DO thanks to the incoming CO2 scrubbing out other matter and blowing it out the headspace (as measured with a DO meter). Even with closed transfers, short of the LODO early transfer natural carb method, it's the most stable method I've encountered.

If you want "simple" just set head pressure to equilibrium and walk away. But why bother with a stone at that point.

 

[Jayf19]

Because my way a corney or sanke keg should be fully carbed in 20 or 30 mins with a decent stone. Likely less. The bleeder valve lets you blast in significant amounts of gas while not overpressurizing your vessel. Plus I've seen routinely a 30% or more reduction in DO thanks to the incoming CO2 scrubbing out other matter and blowing it out the headspace (as measured with a DO meter). Even with closed transfers, short of the LODO early transfer natural carb method, it's the most stable method I've encountered.

If you want "simple" just set head pressure to equilibrium and walk away. But why bother with a stone at that point.

Interesting; not a topic that I am familiar with, I will do more research but your input will serve as a reference / starting point. I thank you for that

 

[chris39]

Not quite sure I understand this part? Is this only for sanke kegs or would something similar be needed on a cornelius keg?

Ha Jayf19
Can you send me the link for bleeder valve thread and parts list for making your own.

Thank you
Cheers
Chris39

 

[windsifter]

Why do you need to slowly increase the pressure every 2 hours in step functions starting around 6 psi? Why not just set the initial pressure going into the stone at the desired pressure + wetting pressure?

 

[doug293cz]

Why do you need to slowly increase the pressure every 2 hours in step functions starting around 6 psi? Why not just set the initial pressure going into the stone at the desired pressure + wetting pressure?

If you start at the desired final pressure, then the flow rate will be too high, and CO2 will just bubble up into the headspace faster than it can dissolve into the beer. Once the headspace is at the set pressure, then CO2 flow will almost stop, and more CO2 will only flow into the keg at a rate only slightly faster than it can be absorbed from the headspace - the same absorption rate you get with set and forget.

By stepping the pressure from just over the wetting pressure, the flow rate will be lower, and less of the CO2 will make it into the headspace. The net result is faster overall carbonation.

Brew on

 

[windsifter]

Makes sense and thanks for explaining so well.

Next question is has anyone automated in in-line regulator that slowing increases the pressure to a set point?
https://www.kegland.com.au/products...rated-gauge-for-water-or-gas-8mm-5-16-push-in

 

[doug293cz]

Makes sense and thanks for explaining so well.

Next question is has anyone automated in in-line regulator that slowing increases the pressure to a set point?
https://www.kegland.com.au/products...rated-gauge-for-water-or-gas-8mm-5-16-push-in

What you really want is an automatic flow rate controller. You would experimentally determine the CO2 absorption rate of your equipment and conditions, and then set the controller to deliver CO2 at that rate. I'm guessing that you would want a rate on the order of 1 liter/hour, plus or minus. That would carbonate a 5 (19L) keg in about 32 hours. I believe medical oxygen systems use flow rate controllers.

Brew on

 

[day_trippr]

I believe medical oxygen systems use flow rate controllers.

I've been hooked up to hospital O2 a few times in my life and the systems have gone from mechanical regulators with flow meters to portable computer controlled systems. I actually chose the model Western Medica flow meter/regulator that I recognized from a couple of my stays decades ago for oxygenating my worts

I believe the modern systems sense pressure drop (inhaling) and provide essentially "on demand make up air"...

Cheers!

 

[doug293cz]

I've been hooked up to hospital O2 a few times in my life and the systems have gone from mechanical regulators with flow meters to portable computer controlled systems. I actually chose the model Western Medica flow meter/regulator that I recognized from a couple of my stays decades ago for oxygenating my worts

View attachment 826894

I believe the modern systems sense pressure drop (inhaling) and provide essentially "on demand make up air"...

Cheers!

The "on demand" flow controllers wouldn't work for carbonation, as there is nothing to cause a transient drop in pressure similar to what happens when inhaling.

I was thinking about O2 flow controllers when I wrote my previous post, but I believe those work at flow rates on the order of a liter/minute, or so, which I think would be too fast for carbonation. I just checked my O2 flow regulator, and it has several discrete settings that range from a minimum of 0.12 L/minute to a maximum of 8 L/minute.

Brew on

 

[day_trippr]

I agree. Yeast don't respire fast enough and my flow meter would be hard-pressed to accurately meter a tenth of a liter per minute...

Cheers!

 

[windsifter]

What you really want is an automatic flow rate controller. You would experimentally determine the CO2 absorption rate of your equipment and conditions, and then set the controller to deliver CO2 at that rate. I'm guessing that you would want a rate on the order of 1 liter/hour, plus or minus. That would carbonate a 5 (19L) keg in about 32 hours. I believe medical oxygen systems use flow rate controllers.

Brew on

Thanks doug. Do you actually use this when carbonating? I found another thread where people were discussing a flow rate controller but didn't look like anyone was suggesting it.
https://www.homebrewtalk.com/threads/co2-flow-meter.698688/
I'd be happy to play with one if someone vouches for it, but if all the experienced folks here don't recommend it or do it themselves, I'm guessing there they've decided it doesn't work.

best,
brian

 

[doug293cz]

Thanks doug. Do you actually use this when carbonating? I found another thread where people were discussing a flow rate controller but didn't look like anyone was suggesting it.
https://www.homebrewtalk.com/threads/co2-flow-meter.698688/
I'd be happy to play with one if someone vouches for it, but if all the experienced folks here don't recommend it or do it themselves, I'm guessing there they've decided it doesn't work.

best,
brian

No, I don't use a flow controller. I put chilled beer on 30 psi for 36 hours, then vent the headspace, and reset the regulator to equilibrium pressure.

I was responding to your question about a regulator that slowly, and automatically increases the pressure over time. I'm not sure such a device exists, but flow controllers do exist, and they will automatically increase the forcing pressure to maintain the selected flow rate, which is what you are looking to accomplish. The question is: are there existing, inexpensive flow controllers whose flow control range is suitable for carbonation, without excess pressure build up in the keg headspace (what happens if the flow rate is faster than the beer can absorb the CO2)?

Brew on

 

[windsifter]

thanks again for the advise and raising others up.