A beer sparkler is a device that can be optionally added to the equipment used to serve cask ale. Its function is to act like a shower head, agitating and aerating the beer that passes through it, forcing CO2 out of solution, resulting in a beer with a thicker, creamier head and softer mouthfeel. The reduction in CO2, along with this softer mouth feel, can also promote sweetness in the beer and reduce harsh bitterness.
Broadly speaking the North of England favours the use of a sparkler whilst the South doesn't. The argument against being that the added stress put on the beer during its journey to glass actually serves to force volatile flavour and aroma compounds out of solution, dulling the hop character and masking the inherent texture on the beer.
Being about as Southern as it gets, the recent Twissup to Burton really opened my eyes to the prevalence of sparklers in the North. Instantly beer feels wrong in the mouth, the texture cloaked by a thick slab of silky head, the aroma losing its battle to cling to the liquid ... perhaps.
As a home brewer, the beer I make myself always seems to taste better than it should. The measure by which you evaluate beer seems to lose all sense of baseline and perspective when you were integral to the brewing process. Beers that you'd ordinarily turn your nose up at instantly become delicious! The same is clearly true of the sparkler debate. If you grew up with sparkled beers, there's a good chance you'll have a preference for beers served in that way. This is both understandable and completely reasonable, beer should be about enjoyment and if a sparkled head does it for you, go for it .... perhaps.
The fairest way to asses which method shows off a beer's flavour most effectively would be a straight side by side, sparkled against non-sparkled. BeerReviewsAndy carried out this test in Burton with Worthington White Shield and suggests:
"In the interests of fairness we tried the White Shield, Red Shield and E with and without sparklers, the beer was in such fantastic condition that even without the sparkler it looked and tasted brilliant." (Full blog here).
The Draft House in Clapham are running a whole night dedicated to the experiment (16th June - 7pm), an event which looks like a lot of fun and a rare pub-led focus on the debate.
Personally I think it's important to remember that the brewer knows how he or she wants the beer to be served. A sparkler might suit specific styles of beer more than others, but ultimately that's irrelevant in comparison to the brewer's intention. As the craftsman of your pint, they know how they intended the beer to be served, it's the barman's responsibility to insure that the beer reaches the drinker in that state.
I think that sparkling every beer as a matter of course is the wrong thing to do. Equally though, if the intention was for a thick head and smooth body, under specific instruction, it would be wrong not to apply a sparkler.
Nobody would serve a half in a pint glass and nobody would serve bitter on the rocks, so nobody should use a sparkler without the brewers direction.
Do you just take a beer as it comes or do you specify whether or not you want it sparkled? Have you grown up with one method and switched for some reason, if so ... why? And before anyone points it out, yes Burton is the North!