I have some crumpled paperbags which I am studying and sketching
The one on the left was done about 2 weeks before the one on the right. I am trying to see the main lines, and to identify 3 major shades. It helped with the latest one that I had a strong light source from the top, so the lines and tones were quite well defined. I used watercolour pencils for the shading, then white watercolour crayon for the highlights.