Kraeusen is the thick, foamy head on fermenting beer.
(German, literally "crown.") (1) The large head of foam that forms on the surface of the wort during the early stages of fermentation. (2) A method of carbonation in which green beer in the kraeusen stage is added to finished beer to bring about a second fermentation.
The period of fermentation characterized by a rich foam head.
The rocky or cauliflower heads or foam that appear on the surface of the wort during the first days of fermentation. Then they reach their peak, they are called high kraeusen.