When it comes to carbonation, the size of the keg can indeed affect the time it takes for the beer to carbonate. Smaller kegs generally carbonate faster compared to larger ones. This is primarily due to the difference in surface area-to-volume ratio.
In a smaller keg, there is a higher surface area relative to the volume of beer inside. This means that more CO2 molecules come into contact with the beer, allowing for faster absorption and carbonation. On the other hand, larger kegs have a lower surface area-to-volume ratio, resulting in a slower carbonation process.
To illustrate this, let me share a personal experience I had with carbonating different keg sizes. I once had a 5-gallon (19L) keg and a 2.5-gallon (9.5L) keg of the same beer. I carbonated them using the same method and set the same pressure. Surprisingly, the smaller keg was fully carbonated in just a few days, while the larger keg took almost a week to reach the same level of carbonation.
The size of the keg is not the only factor that affects carbonation speed. Temperature also plays a crucial role. Cold beer absorbs CO2 faster than warm beer, so chilling the keg before carbonating is essential. By keeping the keg at a lower temperature, you can speed up the carbonation process regardless of its size.
To summarize, smaller kegs tend to carbonate faster due to their higher surface area-to-volume ratio. However, carbonation time still depends on various factors such as temperature, pressure, and the desired level of carbonation. It is always recommended to monitor the carbonation process and adjust accordingly based on your specific preferences.