Author: Johannes Vloothuis, Associate Editor

A believable, professional sky is not done with a blue sky and white clouds. Nature didn't make it so simple. That's why skies are so beautiful. The first thing we have to consider is that from your viewpoint clouds in the sky directly above you (the zenith) are closer than near the horizon. That's where atmospheric perspective comes in and will change the color value and color temperature of the highlights and shadows of clouds. Use this technique to observe a sky: almost close your fist leaving a hole to peek through. This will eliminate the surrounding detail and allow you to judge color and value more accurately. This helps not to fall in the trap of preconceived notions. Skies are lighter and warmer near the horizon, cooler and darker the higher you go. Colors will differ tremendously at different times of the day and seasons. Let's take an early afternoon summer sky as an example. The sky will be a yellow-orange color close to the horizon. As it approaches the zenith it fades into a greenish blue, to blue, finally to a darker violet blue right above you. The ordinary white cumulous and stratus clouds of the summer day recede in color as follows: the whites and near-whites of the clouds become a trifle warmer and darker towards the horizon, while the cloud "bases" or actual shadow portions of the clouds go back a trifle cooler and lighter towards the horizon. The "blue" of the sky, goes back form a resonant blue at the zenith, slightly lightening and warming until the horizon is reached. Upon the graded surface of the blue sky, the "whites" of the clouds are whitest and lightest in value in the zenith. As they recede into the middle sky there is a slight warming of the whites. The shadow portions of the sky will be darker and warmer as they get closer to the zenith. Note: Warmer white will be achieved by adding yellow, pink or orange to the paint. You can warm a cloud shadow by adding a touch of alizarin crimson or orange (If you wish to have a grayer cloud). Subtract this as you recede towards the horizon. Look at the sky portion of one of my paintings below. Match the numbers with the statements.

1. The cloud at the top is darker and warmer than in the horizon. Painted with Ultramarine blue, burnt sienna & a touch of alizarin crimson. 2. The cloud highlights above us are lighter in value and cooler. Same mixture as in #4 with more white added. 3. The cloud shadow Same mixture as #1. Subtract alizarin crimson. 4. Cloud highlights are darker and warmer near the horizon. Yellow ochre and Chrome orange. 5. The blue sky above us is cooler and the value is darker. 6. Near the horizon the sky is lighter in value and starts to take on a greenish-blue hue.

It is important to keep color harmony. We should bring down sky colors into foregrounds and middle grounds. Some touches can be added on the shadows of rocks, in foliage, etc. Just as well if we have green landscape some hints of green can appear in the cloud shadows. This way we are not divorcing our colors. The picture below illustrates such harmony. Note: the image below is presented as rather large, in order to allow you to see more detail. You may need to scroll left/right in order to view the entire image.

1. Some hints of green added into the cloud shadow. 2. Some blue sky color was glazed into the shadow. 3. Some blue sky color appears on shadow sides of rocks, the cactus plant, the tree, etc. 4. Touches of blue on top of adobe stones.