Drawing a rucksack in my studio, using a black oil pastel on paper.

I work with oil pastels and oil bars, which are effectively pieces of oil paint and take a long time to dry. I’ve tried many drawing materials and oild pastel is best at producing a dark solid line. Graphite seems to produce only a weak grey line and marker pens don’t have the depth of oil pastel which raises up off of the page. I try to increase this effect by mounting the drawings on card and then cutting them out.