Crank and Shake Carbonation

The “crank and shake” method to carbonate beer, which has a scrumptious name, is widely suggested and is probably the crudest method imaginable for carbonation. It is simply bad advice given by a fairly large number of people.

Carbon dioxide solubility is affected by two variables you can control; beer temperature and carbon dioxide pressure. The goal of carbonation is usually to dissolve somewhere between 5 to 6 grams of carbon dioxide per liter of beer (in US terms this equates to 2.5 to 3.0 volumes). The units are not important; the important thing is that we have a tangible goal to carbonation.

When adding carbon dioxide to beer using a gas cylinder, as opposed to bottle conditioning, it is best to begin the process with cold beer since carbon dioxide solubility increases as the beer temperature decreases. If your goal is a normal level of carbonation you will be targeting about 5 g/L or 2.5 volumes of carbon dioxide. Consulting a gas solubility chart will tell you that if your beer is 38 °F (3 °C) the corresponding equilibrium carbon dioxide pressure for 5 g/L of carbon dioxide is 13 PSIG (the “G” indicates that this is gauge pressure instead of absolute). What this means is that if you supply 13 pounds of regulated carbon dioxide pressure to a keg of beer maintained at 38 °F (3 °C) that the beer will absorb carbon dioxide until equilibrium is reached. The important thing about this method is the use of a properly functioning regulator and an accurate pressure gauge. That’s an article unto itself, so I will let that thought linger. If you have a properly functioning regulator, gas will flow into the keg as your beer absorbs carbon dioxide. This continues until the headspace pressure ceases to drop over time and that is when the process ends.

In a small keg this takes about three to five days to complete if you simply hook the gas up and leave your beer alone. In larger batches, the process takes longer since the headspace area is small compared to the beer volume. Commercial brewers’ carbonation stones and in-line gas injection systems are used to create a much larger gas surface area and to reduce the time required for carbonation.

You can do this at home by shaking your keg. The important thing, however, is to crank up the regulator to a pressure based on your carbonation goal. Otherwise, the whole endeavor is absolutely aimless. That’s why this method has the lovely nickname, “crank-n-shake.”

So why do people do this? One thing drives this method: speed. If you crank the pressure above the equilibrium target the gas drives into solution at a faster rate. The same is true with all types of equilibria. Take mashing as an example. If you put your mash pot into an oven maintained with a very good thermostat at, say, 152 °F (67 °C) the mash will eventually reach 152 °F (67 °C). This takes hours so we use a higher temperature for heating and then turn the heat down as the temperature approaches the set-point. This is pretty easy to control because we can easily measure temperature with a thermometer and we can respond to this information by reducing the heat and avoiding an over-shoot. But when carbonating we cannot measure the carbon dioxide content of the beer continuously and often end up with overly gassy beer.

So the next time you brew a batch of beer, finish by 1) chilling the beer before initiating carbonation, 2) using the proper equilibrium pressure for carbonating your brew, 3) exercising a little patience — a few shakes a day won’t hurt if you cannot resist the urge.

Response by Ashton Lewis.