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Can anyone tell me how to properly use a carbonation stone to carbonate beer in a corny keg? Particulary how to attach the stone and if it is removed after full carbonation or left in place until the keg is empty

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You can carbonate in 2-4 of days if you increase the pressure slowly. Start at 1-2 psi, and just increase the psi a touch every hour or two. The absolute pressure on the regulator isn't important, just work it up slowly towards your final serving pressure. The key is that the regulator is set to a higher pressure than what is in the headspace of the keg, so that CO2 will enter the keg. You can do this 2 ways: either increase the pressure on the regular, or keep the regulator at the same pressure purge some CO2 from the keg to reduce pressure inside the keg.

Having the keg chilled to serving temperature rather than room temperature will also help it absorb CO2 faster, since CO2 enters solution in cooler liquids faster.

As to removing the stone - my stones are a few years old and have a barb fitting, which is not easy to disconnect, so it's more convenient to leave in place. Some stores are offering carbonation stones with a 1/4 MFL thread so that they can be removed from the end of the hose rather than having to remove the hose itself, which might make moving it between kegs easier. Alternatively, there are corny keg lids with a gas post welded on, that's connected to a hose and carbonation stone. You fit this lid to the keg, hook up the CO2 to the gas post on the lid, carbonate, and when you're done then swap the lid with a regular corny lid. I've not used it, but it sounds like it would make moving the stone between kegs a breeze.

I carbonate my beers using a stone from time to time - I've got 0.5 and a 2 micron stones. The 0.5 micron stone is best - the bubbles are 1/64th of the volume and there is relatively 4x more surface area than the 2 micron stones, so the CO2 enters solution quicker.

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I'll ask you the same question as brewchez: Why ramp up the pressure rather than setting the pressure to serving pressure immediately, as I normally would without a stone? –  Dustin Rasener Aug 25 '11 at 1:22
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The initial velocity of the CO2 bubbles is dependent upon the pressure difference between the regulator and the headspace. If the pressure difference is too high and they're travelling too fast, the bubbles will reach the headspace before there is time for then to be completely absorbed. A small pressure difference helps ensure the CO2 enters the solution at low velocity. The CO2 will naturally accelerate towards the surface, so anything we can do to reduce the starting velocity will help ensure the CO2 has more time to dissolve. –  mdma Aug 25 '11 at 20:35
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I have done this in the past but it has been a while. You will need a diffusion stone and a lenth of 1/4 ID beverage tubing about the length of the height of the keg. Attach the tubing to the end of the gas dip tube and place the stone on the other end. You then set the desired pressure on your regulator and force carb as usual. It is said to carb a bit faster than normal and also produce finner bubbles.

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I have used these before. I attach a piece of tubing to the stone, then the other end to the end of the gas IN dip tube within the keg. Its sort of tough to get it on the dip tube. But if you soak the end of the tubing in some hot water it should make it a little easier.

Then you set the PSI level on you regulator and let it rip. I found that to take real advantage of the stone you should adjust the regulator in two stages. Meaning if you wanted to carbonate at 15PSI, set the regulator to 7.5ish PSI for one full day, then go the rest of the way for the next day or two.

After the beer is carbonated, you can take it out or leave it in. The only real reason to take it out is if you want to use it for a second keg.

I never found that the using a stone was all that much faster but in theory it is a little bit I guess.

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What is the purpose of your two-stage carbonation? In what way does it work better? –  Dustin Rasener Aug 25 '11 at 1:20
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