Draught Operations > A Matter of Balance > Mixed Gas
As we have seen, beer readily absorbs carbon dioxide. Any change in CO2 pressure on a beer results in a change in the carbonation of the beer. Nitrogen is different. Beer does not absorb nitrogen gas to any significant degree. This means we can apply nitrogen pressure to beer without changing the properties of the beer. Thus, in high resistance draught systems, we use a mixture of CO2 and nitrogen to achieve two objectives: 1) maintain proper beer carbonation and 2) overcome the system resistance to achieve a proper pour.
The exact mix of CO2 and nitrogen depends on all the factors we have discussed: beer temperature and carbonation, system resistance and the total applied pressure that’s required. Those interested in the details of these calculations can see Appendix C. While some systems use a premixed blend, other installations may require a custom mix created from separate nitrogen and CO2 tanks by an on-site gas blender.
Another excellent set of resources for determining the proper mixed gas blend, pressure, and carbonation levels in your draught beer system can be found here. The Easy Blend tool determines the exact proper blend for dispensing beer in your system. The Easy Volumes tool will determine the carbonation volumes you can anticipate using a particular set of conditions in your system. And the Easy Presure tool will help you determine the pressure you'll need to use given the other variables in your system.
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