The wort is then moved into a fermentation vessel where yeast is added to initiate fermentation. The yeast converts the sugars from the wort into alcohol and carbon dioxide. Fermentation with bottom fermentation yeast takes place at between 7° C and 9° C and requires some 6 to 7 days, whereby the yeast eventually settles at the bottom of the vessel. Carried out with top fermentation yeast, the process takes 4 to 5 days at 18 – 20° C, with the yeast finally rising to the surface.