Tight edges: Referring to a stack of paper in which the centre of the sheets are baggy. Caused by the stack having a high moisture content. And low humidity of the surrounding atrmosphere. Moisture thus evaporate at the edge and shrink.

• 弓形纸边:指一堆纸的纸晕，向两边伸长面收紧，中间松起的情况。起因是纸堆的水份含量高，环境的空气湿度低，纸边水份挥发，因而收缩。