 For British beers, the most common fining agent is isinglass, and most breweries producing Real Ale introduce isinglass into the shipment cask so that the beer will drop bright readily upon the cask's being breached; this process can take from several hours to two or three days and may require the addition of supplementary finings by the cellarman.In contrast to dropping bright, yeast may also be removed from beer through filtration.The process of filtering removes carbonation and means the beer requires force carbonation.