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.
- Attach your stone to your CO2 regulator.
- Place your stone in a bucket of water.
- Slowly turn up the pressure on your regulator until you start to see the stone emit a fine trail of bubbles.
- 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!