The Line of Beauty is an S-shaped curve that is considered to be the most variable and elastic of the fundamental forms of composition. It can appear within a subject, as the boundary line of an object, or as a virtual boundary formed by the composition of several objects. William Hogarth’s essay on “The Line of Beauty” (Analysis of Beauty 1973), he set forth a series of seven curves, from which he selected the forth one as the most perfect. According to Hogarth, the S-shaped curved lines signify liveliness and excite the attention of the viewer when contrasted with straight lines or right angled intersecting lines, which signify stasis, death, or inanimate objects. This curve can be found in nature in the line of a woman’s back, or if two such curves are joined together side by side, they produce a beautiful curve of a mouth or Cupid’s bow.
This curve is particularly adapted to upright arrangements and we can find it in many of the great figure compositions of the Renaissance. To express this line in the composition of the figures was a constant effort of Michelangelo. He introduced it both in the composition of the single figure and of figure clusters.
The compound S-curve has the perfect balance and is often created in the standing figure, because it has an element of grace and affords the same delight as the interweaving curves of a dance or the fascinating spirals of wafting smoke. Landscape paintings in which a large number of elements are introduced are controlled and dependent on this principle. Many simple subjects owe their force and excellence entirely to a bold sweeping curved line. That being said, when a subject demands a rough and rugged form, it is better to consider exchanging the sinuous line for an abrupt and powerful zigzag.
When painting skies, artists often use cirrus clouds to form a background to the stronger forms of the cumulus in order to create contrast. Such an arrangement often adds great swing and movement in the lines of the sky, carrying the eye away from the horizon. When going for positive cloud motion you can use oppositional masses that suggest wind, with the different strata showing contrasted action of air currents.
You can be creative with it. The “Line of Beauty” can be used in any and all forms of composition.