Among early nineteenth-century artists, John Constable was one of the most assiduous and systematic students of the sky. As a landscape painter he was acutely aware of the sky as the principal source of light and of the extent to which cloud cover, the formations of clouds, and atmospheric effects could influence the appearances of nature. Constable was keenly aware of contemporary scientific study of these natural phenomena, and followed current developments in the recent science of meteorology, as in Luke Howard's seminal essay "On the Modifications of Clouds," first published in serial form in 1803 and reissued in his book The Climate of London in 1818, or in Thomas Foster's book, Researches about Atmospheric Phenomena, published in 1812. The artist felt that a thorough understanding of such natural phenomena would give his art greater truth to nature.

In the early 1820s Constable lived in Hampstead, a village situated just north of London on an elevated, open, hilly heathland that made him especially aware of the sky and its ever-changing effects. It was during his residence there that he made many oil sketches of the sky itself and of the sky set off against the dark foliage of treetops. He painted such works rapidly, usually in oils on paper, working directly from nature in the open air. The paper support enabled Constable to work fluidly, while the relatively absorbent qualities of the paper allowed the studies to dry more quickly than they would on canvas. Constable referred to these painterly exercises as "skying." He often annotated these studies with the date, time of day, wind direction, and the scientific nomenclature invented by Howard for the cloud formation depicted.

Cloud Study: Stormy Sunset is typical of Constable's Hampstead oil sketches of the sky. It is freely and quickly executed, the colors brushed on with gusto, wet paint into wet paint. Yet it conveys vividly the effects of light, atmosphere, and movement in the western sky on a cloudy evening after a stormy day. This oil sketch is not visibly annotated, although Constable may have written on the back of the mounted paper or at the bottom of the image, where slight traces of pen strokes may be the tops of letters from an original annotation, trimmed off the sheet for aesthetic reasons at an unknown later date. This work is one of about forty extant cloud and sky studies by Constable. For him, such sketches were not so much works of art complete in themselves, as raw materials gathered in the field, empirical research matter that would serve to better inform the naturalism of his more finished exhibition pictures worked up in the studio. Toward the end of his life, in the 1830s, Constable's art became more emotionally charged. He increasingly regarded the sky as "the chief organ of sentiment" in landscape painting, and very likely looked to his cloud studies more for their expressiveness than for their empirical or scientific content.

(Text by Philip Conisbee, published in the National Gallery of Art exhibition catalogue Art for the Nation, 2000)