I am about to take an extra batch of rabbit skin glue (1 cup) made to the same ratio for gluing the fabric to the panel that I demonstrated in the previous posting (1 part glue to 11 parts water,) and heat it up again to make some gesso. This glue has been sitting in the fridge overnight and, as I hope you can see here, has formed into a thick gel. I set it on the stovetop burner and slowly heat it up to 130°F, stirring it occasionally. The electric burners on my stove dial go from 0 to 10, and I set them at about 3 to 4 to get them as hot as I need. A good portable hot-plate with temperature controls would keep you out of the kitchen.
This mix of solids is 1¼ cup of gypsum and ¼ cup of titanium white pigment. I slowly sift the solids into the glue a little at a time, stirring it in very slowly. When all the solids have been transferred to the glue, I continue a slow stir until it all becomes a smooth liquid. If you add a teaspoon of alum powder it will help reduce the absorbency of the gesso when it dries on the panel.
You’ll notice that gesso is not nearly as thick as paint or the acrylic “gesso” you may be more familiar with. It’s about the consistency of heavy cream, which is exactly how you want it… almost. The next step I recommend is to refrigerate it for a few more hours. This will cause the glue to gel again and any air trapped inside will be squeezed out, giving you a smoother mixture. You could apply it now if you wanted to, but I think you’ll be happier if you wait.
Next I’ll show the gesso being applied to the panel.