I want to sketch with charcoal on canvas board, then gesso the board before painting with acrylics. Will that work? Why or why not?
As far as I know, all gesso is opaque—either white or black. Therefore, it will cover up your charcoal work and you will not be able to see it. Further, gesso is generally applied with a brush and would smear your charcoal drawing. To do what you are describing, you need to spray your charcoal sketch with a clear fixative (either charcoal fixative or a crystal clear water-based varnish. This will seal your charcoal sketch and allow you to paint over it with your acrylics without smearing your charcoal.
Hope this helps.
Judy Leasure, TDA
My art blog: http://www.jalstudios.blogspot.com
My art pictures: http://www.picturetrail..com/jleasure
My art store: http://www.jalstudios.etsy.com