Torsion tube belongs to technology. Twisted tube originally refers to a method of twisting fingers on the flute when musical instruments play the flute, and later it is applied to calligraphy. In Yuan Dynasty, Chen Yi once said: "Twist the barrel. Thumb and middle finger twist the pipe head. " Twist tube, simple to say, looks unnatural at first, but if you are familiar with it, you will get twice the result with half the effort after skilled use. If you decompose the four compositions according to the description of the painting, and add this action, there will be five. From this perspective, we can't underestimate Wordsworth's writing.
At the end of the painting, you need to pause the pen and twist the tube. When twisting the tube, you don't leave the brush in the original position, but you need to twist the tube and move the pen to the right. At this time, you need to gradually raise your pen to realize the transition from heavy to light. At this point, a good painting was written.