The “Stroke” of genius-Above are my favourite techniques for creating the illusion of gradations in value using high contrast black ink on white paper. Look at thick and thins. Nib pens are great for this. Draw structures in shadows with thicker lines, and structures in light with thinner lines. Try it yourself: draw a circle, then go over the bottom of it with a heavier line and immediately it gains volume and looks like a ball.
