The colander separates the very highest quality Grade A beans from those labeled Grade B; the two grades are sent separately down the hill in a water chute with a 1 percent gradient.[26] This process allows for further separation of beans based on quality, with around 15 tanks available at the bottom for capture of the different types. The beans are kept submerged, two days for the best and 15–20 hours for the lesser beans, which causes a small amount of fermentation to convert the remainder of the sugar without significantly impairing the flavour.[26]