Personally, I use the strong and vivid colors of pastel for large, modern shapes, while charcoal only as an additional tool to emphasize the meaning of important topics such as Creation or the Tree of Knowledge. of Paradise among the graphite lines.
However, pastel is originally, as the name suggests, used for light shades giving a slight impression of duration, charcoal is usually simply used as is to form black outlines on torn and lightly colored paper. special rough pastel-charcoal available in white and other colors.
In order to keep the luster of the pastels and to dilute the charcoal with the fingers, thus destroying the shapes made on the surface, the image must be fixed once by a special pastel-charcoal spray or twice by spraying with hair spray. In both cases, you should not spray too close to the paint and do not apply too much product so as not to make the paper too wet.
In all cases, the paper should be dried before it is rolled up and placed in a frame.