When with pens you draw traces, with pencils you draw stains or smudge the surface area, as For anyone who is drawing with a brush. By drawing strains with different levels of spacing among them (or with various line widths), you may develop an illusion of different brightness values. https://cruzyqfvh.answerblogs.com/35134635/ink-drawing-for-beginners-no-further-a-mystery