In nature, fog varies from a pale, translucent mist to thick, opaque blankets of white. When drawing fog, use charcoals and a blending stick to achieve this range of density. By blending vast areas of shadow, you achieve the feathery nature of fog and capture its opacity. If you wish to make a more authentic sketch, use coloured paper and a white pastel for your drawing. This will give your image the pale, white appearance of fog in nature.
Use your pencil to sketch a rough area of shadow over the region where you wish to make the fog most dense. Shade in light, horizontal motions. Turn your pencil tip on its side, and move your hand back and forth as you shade to create loose, broken lines of shadow.
Drag the blending stick over the shadows in horizontal motions. This will diffuse the dark region of shadow, making it lighter and more transparent.
Use the blending stick to extend the charcoal shadow in all directions. Because charcoal pigment is loose and dry, the blending stick acts as a pencil to create soft shadows.
Add a few light strokes of charcoal to regions of the fog that you wish to darken.
Go over the strokes of charcoal with your blending stick to soften the dark colour.
Use the tip of the blending stick to soften the charcoal shadows around the edges. Use circular motions to achieve a light, cloudy effect.
Go over the entire region of fog with the blending stick in large, circular motions. This will soften the horizontal lines and create a diffused, cloudy look.
Charcoal pencils create very dark shadows, so do not apply heavy pressure to your pencil when drawing a light, airy subject like fog.