CTC (crush, tear, curl) differs from orthodox production solely in that, after rolling and before fermentation, the tea is uniformly shredded with a CTC machine, so shortening the overall production time by approx. 50%. This method yields powerfully flavored, quick brewing teas which, while they are not of very high quality, are particularly suitable for producing tea bags. A distinction is drawn between the China tea plant (e.g. from China, Japan and Taiwan) and the Assam tea plant (e.g.. from India, Sri Lanka, Indonesia and Vietnam), each variety yielding both leafy and broken grades of tea. Teas are also classified and graded depending upon the size of the tea leaves. The youngest, small top leaves (= pekoe tips) provide the most valuable teas, while the older, large bottom leaves provide less valuable grades. • Tea has a long storage life of 18 months or more provided that proper transport and storage conditions are maintained. However, this does not apply to aromatized teas. • Moisture content: 4-6% Grades of tea are classified by: • Country of origin • Leaf size/shape To produce black tea, leaves are harvested and withered and then crushed, torn, curled, or rolled and allowed to oxidize before being dried. As a result the leaves darken and develop a stronger flavor and aroma.