Chinese watercolors are usually done on rice paper with natural colorings extracted from tree and plant resins. Each painting has to be stretched before it can be mounted onto a scroll or framed. The stretching procedure involves brushing the finished painting with a wet paste and stretching it overnight on a board. Most ancient paintings were done by the contour method in which the subject matter was first outlined and then several layers of color were applied. As a result, the paintings were detailed reproductions of the subject matter. However, at the beginning of the Ching Dynasty, a style moving away from the contour method started to emerge. In 1879, a new style of Chinese painting was born. Unlike the traditional detailed contour, this style had no border lines. Instead, it was impressionistic. This style was first developed by the Kao brothers, Kao Chi-Feng and Kao Chien-Feng, and later became known as the Ling Nan school.