painting skies and clouds in oil

Mix a sky blue, build cloud masses, and handle edges and brushwork in oil, using Dutch ground methods and five measured paintings as guides.

7 min read

In most landscapes the sky is the largest single shape and often the lightest. Study it as one luminous mass first and as individual clouds second. In Laura Knight's painting the sky and clouds read, when you squint, as a single light mass separate from the earth and structures below. If you get that relationship right, the clouds only need to be convincing inside it.

This guide covers a sky blue that does not go cold, cloud values, brush direction, and edges. It also covers two old-master methods for getting air into the paint.

What you need

Titanium white, the main light for clouds and sky tints.
A blue: ultramarine or cerulean. Both appear in the sky mixes of the example paintings.
Raw umber, to take the rawness off the blue.
Yellow ochre and raw sienna, for warm light near the horizon and for warming a pale sky.
Burnt umber, for cool grey mixes on the lower edge of clouds and for the land beneath.
Turpentine and a little linseed oil. A first painting in turpentine alone dries dead and stays slightly absorbent, while much oil darkens the colour [1].
A palette knife and a rag, for lifting off paint that will not settle [2].
Wide flat brushes and a softer blending brush, for broad horizontal strokes and for softening a few edges.
Optional: a canvas toned in advance with a raw sienna or dun-coloured layer [3].

Step by step

Squint at your subject and decide where the sky sits in the value order. In the Vanmour view the sky is the lightest zone and the city below is the darkest. Fix that order before you mix anything.
Choose your method. For a direct sky, go straight to step 4. For the Flemish and Dutch route, block in the cloud and land forms first in a brown such as raw umber or burnt sienna. Let that dry, then tone the whole canvas with raw sienna cooled toward a dun colour [3].
Paint the first layer lean. Use turpentine for the first painting [1]. If the paint will not settle or works up, lay blotting paper on it, or scrape it off with the knife and rag and repaint with less oil [2].
Mix your main sky colour. Knight's mid-tone sky is ultramarine, titanium white and a touch of raw umber. De Smet's pale sky is cerulean and white with a touch of yellow ochre for warmth. Mix a generous puddle, because this is the most voluminous colour in the picture.
Apply the blue thinly. Dutch landscape painters laid the sky blue thinly over a dry ground so that the ground showed through, which gave air and prevented coldness, and the effect shows in their clouds as well [3].
Grade the blue. Goethe's account of sky blue is the dark of space seen through lit vapour: intensely blue on a high mountain where the vapour is thin, paler in the valleys, and in some regions a very pale blue because of the vapour in the way [4]. Whatever you make of the physics, the observation holds: the sky is lighter near the horizon than overhead, so grade it. Keep the tints clean as well. Ultramarine leans to violet when it is let down with white, so if the pale sky looks mauve, warm it with a touch of ochre rather than adding more white.
Add the cloud lights. Knight's cloud highlights are titanium white with ultramarine in a high ratio of white. Vanmour's lit cloud tops are warm cream, titanium white with yellow ochre. Pick the temperature that matches the light in your scene.
Add the cloud shadows. Vanmour's cloud shadows are a pale grey of yellow ochre, white and a touch of ultramarine. Keep them light. A shadow side that is only a darker version of the lit side usually looks wrong, because shadow colour depends on the light reflected into it [5].
Run your strokes with the cloud. Knight's sky is blended smoothly with visible strokes that follow cloud movement. Vanmour's clouds also carry loose directional strokes that follow their form. Titian tied his clouds together with long horizontals [6].
Finish the edges last, using the notes below. Then step back and squint again to check that the sky is still one mass and still the lightest.

Warm and cool across the sky

Cole's sky shows how temperature builds depth. It moves from cool purples and mauves in the upper corners to warm golden-orange along the horizon, and the clouds on the right catch the light in warm tones. The brightest part of that sky is a golden mix of yellow ochre, white and a touch of red.

A warm veil can also unify a whole picture. Turner's atmosphere in the Dido painting comes from a warm scumble across the sky, hills and middle distance. Behind it the figures and incidents were painted sharp first and then fogged by the semi-opaque wash [7]. Let the sky layer dry before you try this.

Church's sunrise shows the same temperature logic pushed to its limit. The record describes a value scheme of near-black tree silhouettes against a luminous centre, with the clouds shifting from cooler purple-blue shadows to warmer pink-coral highlights, and the most intense light held to a horizontal band at the horizon. Every cloud edge there is soft and feathered; the only crisp edges are where the foreground trees cut against the sky.

Edges and brushwork

Vary the edges within one sky. In Vanmour's clouds the edges are soft where cloud meets sky and harder where one cloud overlaps another. Cole's sky keeps visible horizontal strokes that are not heavily blended, which gives a sense of wind. De Smet uses loose, confident horizontal strokes across the sky and does not overwork them.

Put your sharpest edges in the foreground and let the distance go soft. Cole's distant mountain is blended and hazy against the sky, while the figures and ruins carry the most defined edges.

Common mistakes

Painting the sky as a flat coat of one blue. Grade it lighter toward the horizon [4] and shift its temperature, as Cole does.
Making cloud shadows too dark or too saturated. Keep them light and grey, as in Vanmour.
Using pure white for every cloud. Cloud tops can be warm cream rather than white.
Blending everything to a uniform softness. Keep a few harder edges where clouds overlap.
Painting the blue thickly and opaquely over a wet, oily layer. Thin, lean blue over a dry ground lets warmth show through [3][1].
Letting the land compete with the sky. In Knight's painting the lightest lights are the sky and clouds, and the earth is kept in a separate lower mass.
Over-blending the strokes until the surface loses its direction. Keep strokes that follow the cloud movement.

Study these paintings

gypsies-caravan-and-pony-by-laura-knight: Look at how the sky and clouds sit as one luminous mass above the darker earth and structures. Notice that the sky is blended smoothly while the strokes still follow cloud movement, and that crisp edges appear only where objects overlap sharply, such as the chimney against the sky.

haystacks-by-gustave-de-smet: The pale sky occupies the upper third and is the cool band at the top of a three-band structure. Study the loose horizontal strokes in the sky and how little they are overworked. Note the touch of yellow ochre that keeps the cerulean from going cold.

mount-aetna-from-taormina-by-thomas-cole: Follow the sky from cool purples and mauves at the corners to golden-orange at the horizon. The clouds on the right are warm and catch direct light. The horizontal brushstrokes are visible and not heavily blended, so the sky has direction.

view-of-istanbul-from-the-dutch-embassy-in-pera-by-jean-baptiste-vanmour: The sky is the lightest zone above a dark city. Find the warm cream of the cloud tops and the paler grey of the cloud shadows. Compare the softer edges where clouds meet sky with the harder edges where they overlap.

above-the-clouds-at-sunrise-by-frederic-edwin-church: The sky is nearly the whole picture. Squint and you get three values: black foreground trees, a brilliant horizontal band at the horizon, and a wide middle range of purple, lavender and pink cloud. The record gives the cloud shadows as ultramarine and alizarin, the lit cloud masses as alizarin, white and a little yellow ochre, and the brightest band as white with yellow ochre and a trace of alizarin. Note that the sky moves through colour shifts rather than value steps, and that no cloud has a hard edge anywhere.

Sources

The Practice of Oil Painting (Solomon J. Solomon (1910)), CHAPTER XV PAINTING IN COLOUR DIRECT FROM LIFE-
The Practice of Oil Painting (Solomon J. Solomon (1910)), STILL LIFE IN COLOUR
The Practice of Oil Painting (Solomon J. Solomon (1910)), THE DUTCH SCHOOL
Theory of Colours (Johann Wolfgang von Goethe)
The Elements of Drawing (John Ruskin)
The Practice of Oil Painting (Solomon J. Solomon (1910)), THE SCHOOL OF TITIAN
The Practice of Oil Painting (Solomon J. Solomon (1910)), THE FRENCH SCHOOL