This is fantastic Jacob. I wish I could be more helpful (from experience) on the fixative and paper fronts—but I am not sure how different materials react to it (specifically the acrylic medium.) I do know a number of artists that “fix” graphite or charcoal for an oil painting. As to paper as a substrate—I know there are papers made for oil painting (blick carries a number of lines here: https://www.dickblick.com/categories/canvas/painting-papers/oil/). I remember one of my teachers priming cheap brown paper with acrylic mat medium (25%), mat varnish (25%), and water (50%) for oil painting studies. I do not think there was any concern for the archival quality though. Also, I would assume that the paper would be prepped for use with oil paint first, then graphite or charcoal, then fixative. But again—just speculating.
In regards to painting on fixative I know that Natural Pigments founder George O’Hanlon mentioned that his only concern was that the fixative film not be solid, continuous film, so as to create a significant barrier between the oil and the ground—thus creating a potential scenario for the hampering of the oil paint’s adhesion to the ground. Artist John Bickford with Artist’s Magazine goes into some additional considerations here:
Assuming you’re applying your fixative correctly, this process shouldn’t threaten the bonding of your oil paint to the acrylic ground, whether or not the canvas is factory-primed. If you overapply it, however, you risk sealing off your ground layer, which could cause adhesion problems. Oil paint needs to absorb slightly into its ground to adhere securely, and the more fixative you apply, the more it becomes like a varnish, preventing any penetration. In the extreme, the effect would be something like the adhesion problems often seen with oil painting on glass.
Remember that while fixatives help reduce the chances of smudging they’re not designed to completely withstand all mechanical action, such as the more vigorous passes of a paintbrush. If your technique is rough, then the act of painting may disturb your charcoal underdrawing with or without fixative. If you havent been bothered yet by the accidental incorporation of charcoal particles into your oil paints, and if youre worried about adhesion, then perhaps you wouldn’t miss the fixative if you omitted it altogether. Try painting directly over your drawing or choose a drawing medium, like pencil, that’s less likely to smudge.
On the other hand, if you plan to allow elements of your sketch to remain visible in your final composition then fixative remains a good precaution against future abrasion. Apply the fixative lightly to keep from soaking the charcoal, which, like pastel, is a medium of dry particles that loosely bind to the surface. A light spraying of fixative, which is a low concentration of a resin (such as acrylics) in a solvent, is enough to hold the charcoal in place, while a heavy coat would defeat the charcoal’s delicate purpose. Again, this shouldn’t affect the adhesion of your oil paint, regardless of whether the canvas is primed.
Finally, beware of the potential for discoloring the ground with the fixative if part of your sketch is to remain visible. While acrylic fixatives shouldn’t cause any discoloration, those made with shellac or other natural resins most certainly will.
Hopefully this helps somewhat! Please keep us posted!
