Jets of liquid nitrogen vaporize out of beer bottles necks, during a demonstration of nitrogen bottle-fobbing, arranged at the 2013 Craft Brewers Conference.
Fobbing during bottling is important in forcing oxygen from the bottle before capping. As the bottle leaves the filler, foam rises to the top of the bottle, due to the drop in pressure, displaying the oxygen in the bottle's headspace. This is known as "capping on foam." Bottling lines will often employ liquid nitrogen or sterile water "jetters" [to create fobbing].
—The Oxford Companion to Beer
The 2013 Craft Brewers Conference —presented by the Brewers Association— was held the last week in March, in Washington, D.C. (for the first time in its 30 year history).
Walter E. Washington Convention Center.
28 March 2013.