A burro is a large pile of tobacco built for the second fermentation, after the leaf has been sorted and moistened again. Trade sources describe burros four to six feet tall and weighing thousands of pounds. The greater mass makes the pile run hotter than the smaller first-stage pilones, so workers watch the temperature closely and take the burro apart and rebuild it before the tobacco burns out. Not every factory uses the word; some call every fermentation pile a pilón. See fermentation.