Vinification of Madeira Wine Blandys 10 Years Verdelho: Fermented with natural yeasts at a temperature of 18 to 21ºC in temperature-controlled stainless steel vats. Approximately after 4 days, fortification is carried out with wine alcohol (96% v/v), in order to maintain the desired natural sugar content. Aging: Aged for 10 years in American oak casks according to the traditional ‘Canteiro process.