This device has recently appeared in canned beers in an attempt to mimic the taste and appearance of a true draught beer. It employs a small plastic bladder filled with a mix of nitrogen and beer at the bottom of the can. When the can is opened, the mixture is forced out through small holes in the bladder causing considerable turbulence at the bottom of the can. This results in a thick, foaming head of creamy bubbles. While not real ale (see next), this process does mimic the serving of beer through "swan necks" or "sparklers" and is the subject of much debate.

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