I used lamp black and charcoal gray for the dark undersides of the clouds in this sketch. To soften the edges of the dark brush strokes (applied to dry paper), I diluted the pigment on the brush and drew it parallel to the initial stroke, as one would execute a graded wash. Toward the bottom of the page, closer to the horizon and further away in distance, I introduced Payne’s gray. I hoped that its bluish tint would give the impression of depth.
The overall image is flat with respect to tonal values. The darkest dark isn’t dark enough as compared with the whitest white (which is the white of the paper). This is the reason I refer to this sketch as an ‘underpainting’. I hope to be able to remedy this.