Stumping means softening, toning down, blending, shading… Multiple definitions for such a simple gesture! Choose the most appropriate one for the effect you want.
What you need to know
The softer the medium you use, the more you can stump it. Why? This is because it leaves more drawing material residue on the paper for you to spread around. Charcoal and sanguine are the materials that stump the best!
To blend
Would you like to smooth irregularities in the grain of the paper in areas with drawing material on them? Make your pigment penetrate by rubbing the area lightly with a cotton rag. To darken the area, keep adding layers of drawing material.
Blending and shading
Would you like to smooth the contrast between two juxtaposed gray values? Rub your index finger from the darkest area of the paper to the lightest one. Your slightly oily, damp finger will pick up the residue and gradually drag it along.
Shaping
You can use the stump like an eraser to create a negative drawing. How it works: gray your surface, then remove the drawing material with the stump. Vary the stump pressure to obtain various tones.
Blending stumps have tips at both ends. Use one for dark areas (to gradually pick up the drawing material) and another for light areas (that will stay cleaner).
