A sparkler (also called a sparklet) is a device that can be optionally attached to the nozzle of a beer engine. Designed rather like a shower-head, when beer is dispensed through a sparkler, the beer becomes aerated and frothy which results in a beer that has a noticeable head on it. Some CO2 is carried away into the head, resulting in a softer, sweeter flavour due to the loss of normal CO2 acidity.
There is some dispute about the benefits of a sparkler. There is an argument that the sparkler can reduce the flavour and aroma, especially of the hops, in some beers. The counter argument is that the sparkler takes away harshness. A pub may favor sparklers because the larger head they produce means it does not need to supply as much beer.
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