Which gas is best? Co2, 60/40, 30/70 or 50/50? (50/50 is mainly available in Ireland).

This is a question we get asked lots! We always recommend using mixed gas in environments where the temperature cannot be controlled, unless the brand specifically states co2 should be used. Read more on why below.

Why does the beer that is already carbonated need more gas?

The dispense gas does two things; it keeps the product carbonated, and also pushes the drink from the keg to the tap. If you think what happens when you open a bottle of beer (or any other carbonated drink), when you release the pressure of the cap, the co2 in the product breaks out of solution and escapes. This is what you don’t want to happen inside the keg or your beer will go flat! 

The trick is to keep the co2 in solution with the beer so it stays fizzy. When the bottle example above is likened to a keg setup, opening the dispense tap would be the same as removing the bottle cap. With this in mind, the gas needs to be at the correct pressure to keep the co2 in solution, and also have enough pressure to push the beer from keg to tap.

In most instances, the pressure needed to keep the co2 in solution (as low as 15psi) is much less than is required to propel the beer to the taps. Turning up the pressure of the co2 to get an acceptable pour speed would result in over carbonation of the beer. Also, temperature plays a big role in co2 absorption. The higher the temperature, the more co2 is absorbed.

What are the differences between co2 and nitrogen?

In basic terms, nitrogen isn’t as easily absorbed into solution as co2. This makes mixed gas an ideal choice for dispensing. The co2 keeps the beer fizzy, and the nitrogen provides the extra push needed to get the beer to the tap. Most mixed gas setups will run at around 36psi, almost double that of co2 alone.

What’s the difference between mixed gas and co2?

Mixed gas contains both co2 and nitrogen. The numbers (60/40, 30/70, 50/50 etc) denote the percentage of each gas within the bottle. The co2 content is always stated first, so a 60/40 gas bottle will contain 60% co2 and 40% nitrogen.

Which mixed gas is right for me?

Generally, 60/40 gas is used for lagers, ciders and kegged ales. For Guinness and products with a creamier serve (John Smiths Smooth etc), then 30/70 gas must be used.

How can I tell the difference between gas bottles?

The main difference between co2 and mixed gas bottles is the primary regulator fitting. Co2 bottles have a male thread that protrudes from the bottle, mixed gas have a female thread. As for the different content mixes between mixed gas, all reputable suppliers will clearly mark the bottles. Generally, 60/40 gas is marked with a white label or tag, 30/70 is marked green, and 50/50 is purple. These are also the industry standard colours for the gas pipework which should be used.