Brunello di Montalcino is also made from 100 percent Sangiovese Grosso. Before harvest, the grapes are individually checked on the vines and cluster thinning is done. During harvest, the grapes are checked once more on a large table before being destalked and placed in the fermentation bins. Then the grapes are left to macerate for a certain period, according to the vintage. Spontaneous fermentation starts and the temperature is automatically controlled so that it does not exceed 34C. The must macerates for three to five weeks, depending on the vintage, in order to obtain greater concentration and structure in the young wine. The wine is then transferred to wooden oak barrels of 25 hectolitres (6,600 US gallons), where the malolactic fermentation takes effect. After 2 - 3 years of maturing in the barrels, when the wine becomes stabilized and appears brilliant, it is bottled without using a filter. The wine is left to mature in the bottle for at least one year before labelling and release.