Introduction to inner painting: Painting is done on the inner wall of a transparent glass bottle, so it is called inner painting. It is a precious arts and crafts. Use a special tool to sharpen and bend the bamboo stick to make a shaped bamboo pen, dip it in paint, put it into the mouth of the bottle and paint on the inner wall. The mouth of the bottle is narrow, making it difficult to operate, and it cannot be drafted or corrected, so it is difficult for those who are not skilled and confident to do it.