"Dense and airtight, sparse can ride a horse" comes from the educational reading book "Art Boat and Double Drum" packaged in Qing Dynasty: "Painting and calligraphy can ride a horse in sparse places, while dense places are not ventilated, and white often counts as black."
In calligraphy and painting, sparse places can make horses gallop, and dense places can't even penetrate the wind. The space (white) between lines is arranged as a real painting (black).
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China painters often emphasize the contrast between the density of paintings and calligraphy, and oppose the phenomenon of equal treatment and listing. Sparse refers to an empty place where you can escape and run for horses, while dense refers to a dense place where even the wind can't penetrate.
This can be explained by Li Sixun's Sailing Pavilion, which is said to have been made in the Tang Dynasty. He concentrated mountain trees, figures and other physical objects on the left, painted houses in the gaps between trees, and there was a sea on the right, dotted with one or two sails, which was endless.
The blank space of calligraphy is precisely to set off the dense parts to enhance the ethereal image, so as to get twice the result with half the effort, just like the rest in music, giving people more room for tears. There are more silent stories than talking.
The dense parts of the composition should be more concentrated and portrayed more accurately, so that the pen and ink, color and lines can give full play to the effect. In contrast, the white part is whiter and the dense part is more prominent, giving the audience a stronger impression, thus giving play to the professionalism of plastic arts. Imagination and reality are inseparable, and they are two aspects of composition methods. It is inappropriate to emphasize any one aspect in isolation.