It’s quite hard to appreciate just how dark a blue sky can be. Before I attempt a pastel, I make a tonal study, working from the colour subject (in this case, I’m working directly from a photo I found on the internet). These are the first two stages: I begin by putting in the darkest areas, noting that the sky is darker at the top than near the horizon. Then I add the dark underbellies of the clouds. If I need to lighten some areas, I use my putty eraser. I’m not trying to imitate the shapes exactly, but I’m attempting to understand the characteristics of these clouds.
The next stage is to add the highlights: the parts of the clouds that are reflecting the sunlight. This is done with chalk for the larger areas and white conte crayon for finer details. After that I add more detail to the tones inside the clouds, and draw the wisps above the main cloud with the conte crayon.
This is the final stage. I’ve added chalk to the rocks in the foreground, but this is merely a texture and is not meant to be as bright as the white of the clouds. I’ve put another cloud into the left of the picture as I felt it would improve the composition. I now feel ready to do a colour version in pastel.