A normal picture album is that the painter (or calligrapher) first makes calligraphy and painting and then mounts it into a picture album. Like general mounting, it has to go through processes such as supporting the heart and supporting the back, which means that at least two layers of paper must be supported behind the calligraphy and painting paper. These two layers of paper are generally different in grade because of their different functions, and the grade is generally lower than that of painting and calligraphy paper. Compared with Xuan paper for painting and calligraphy, the paper on the back is generally not suitable for painting and calligraphy.