Paper in China was produced as a series of dipped layers mounted, when finished, on a thick backing. Over time, scrolls need to be remounted and, in some instances, underlayers are removed to facilitate remounting. In such cases, where the ink has penetrated, the lower layers may retain the image of the original composition. Although the original hand of the artist can never be regained, the thin lines and dry brushstrokes, which are absent on underlayers, can be retouched. Consequently, underlayer paintings are more than copies, and are especially valuable if the original painting no longer survives.
Copying is also inseparable from the development and teaching of the arts of China.
Ink on paper rubbings and woodblock prints in the form of calligraphy copybooks and painting manuals have provided standard models for teaching through copying. Like a musical score, the rubbing or print provides an outline to which an artist must supply expression in brush and ink. Even today, in the art historical study of painting and calligraphy, exhibiting copies side by side with their original models is crucial to understanding the copying process, and should be an important aspect of any teaching collection. Consideration of copying as a process raises many other issues including workshop practices, multiple copies by the same artist, relation to mass reproduction, and the historical periodization of copying tendencies. This perspective also encourages art historians and collectors to move beyond seeing art as a pantheon of original masterpieces against which others are judged since even an original, such as a Ni Tsan landscape, imitated paradigms of the past.