I have just completed 3 basswood painting panels; one 11 by 14, one 12 by 16 and one 16 by 20 inches. They are of 3 or 4 butt joined boards with hide glue, the joints previously keyed with a toothing plane. I hand planed them flat with a coffin smoother and am ready to finish and gesso.
My plan is to seal the basswood with a couple of coats of linseed oil / turpentine and allowing them to dry completely. Out here in the West, things dry quickly. I will then cover one side of the panels with a couple of coats of gesso, a mixture of rabbit skin glue and marble dust. The skin glue is fairly flexible but should I add some glycerin to help plasticize it?
Also should I key or tooth the face of the panels for the gesso? I would do this prior to the oil/turps.
I am flirting with disaster here, many old wooden painting panels have failed because of the difference in the shrinkage coefficient of the painting/gesso/substrate. I hope by finishing the panels with oil first I can ameliorate the problems.
Should the back have additional coats of oil to help stabilize? Is the gesso a finish or will it act like a veneer or glue line?