When painting a sky with acrylic paint, it is important to remember to paint in layers because the paint dries fast. Clouds are usually part of the sky and can be painted easily on top of a base coat of paint representing the sky. The technique used to paint depends on the time of day and the weather conditions of the painting.
Partly Cloudy Day
When painting a blue sky on a partly cloudy day, the sky and clouds may provide a frame or bring emphasis to other elements of the composition. Near the horizon, paint a lighter shade of blue. Add white to Prussian blue to create the correct tone for the sky. Let the blue tones dry before painting the clouds. After the blue has dried, use drybrushing to paint the clouds. Dab a round brush very slightly into white paint. Jab the dry brush onto the canvas with a curling motion for the clouds. Add gray tones to create contrasting values.
Overcast Day
For an overcast day in a darker painting, use white and black together to make an gray. Use a touch of red, green, or yellow to give the sky an interesting glow. Paint the base shade of paint first. Be sure to paint the entire sky first before adding the clouds. When the first layer is painted all at one sitting, this prevents color divisions and keeps a consistency throughout the sky. Layer clouds on top of the initial layer after it has dried. Also, use white and black together with a dry round brush to paint the clouds. The clouds should be slightly lighter toward the horizon as darker objects appear closer than lighter objects in the painting.
Sunrise or Sunset
In a sunrise or sunset, the rays of the sun may shine through the clouds. It is important to match the color of the rays with the clouds or sky colors that are behind the rays. Paint some beams of the rays brighter than others. Remember that elements just above the horizon should be brightest. Use red with white for the clouds and add a very light amount of gray to add value. The sky itself will still be blue in some places, and it should be a lighter shade of blue for the sunrise, and darker for the sunset. Use yellow around the horizon to represent the sun's rays. Again, paint the sky first without the clouds, and then layer the clouds over the sky.
