The branches of the paper mulberry shrubs are harvested in the autumn, so the fibre can be processed and the paper formed during the cold winter months, because the fibre spoils easily in the heat. The branches are cut into sections two to three feet long and steamed in a large kettle, which makes the bark shrink back from the inner wood, allowing it to be pulled off like a banana peel. The bark can then be dried and stored, or used immediately. There are three layers to the bark at this stage: black bark, the outermost layer; green bark, the middle layer; and white bark, the innermost layer. All three can be made into paper, but the finest paper is made of white bark only.