Double dropping
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Double dropping or the dropping system is a brewing method for the production of ales. During the early 20th century it was the most popular method of fermentation for English ales, but its use has seen a great reduction due to brewers using artificial methods to obtain largely the same effect.
During the double dropping process the wort is first fermented for a period of time before being 'dropped', under gravity or by other means, into a lower vessel where it continues fermentation. The dropping process has two primary effects on the beer being fermented.
First, 'floc' (dead yeast and other impurities) that has settled during the first period of fermentation will be left behind, purifying the remaining wort; this is said to prevent a 'cardboard' flavor from developing. The degree to which floccing occurs depends on several factors such as vessel shape and dropping speed, hence the need for static brewing vessels in order to get consistent results.
The second effect of the dropping process is the aeration of the wort, which results in a period of accelerated yeast growth, producing more complex and subtle flavors. Brakspear attributes the butterscotch (diacetyl) flavor common to all its beers to the double dropping method.
