Rabbit Skin Glue - do you need it?

[Richard Bingham]

If a canvas is to be prepared with any type of oil ground, natural fibers (linen, cotton, hemp) must be isolated against the absorption of oil with glue size.

Good quality RSG has no particular odor. High quality glues come in a fine powder best dissolved by pouring boiling water into a clean enamel container while sifting in the glue, just like making "Jell-O".

Coarser grades of hide glues (not necessarily from bunny-wabbits) can be rather malodorous. They come in pellets the size of coarse sand to wheat grains which require soaking overnight in water before heating to liquid and are not the preferred material for preparing a painting ground.

Proper proportions are six tablespoonfuls of dry glue to a quart of water (preps approximately 50-60 square feet of canvas). Cold glue can be returned to liquid by gently heating in a double boiler. It is unnecessary and inadvisable to "cook" hide glues, or to heat them beyond the low temps required to liquify them.

Initially, give the raw canvas a "drink" of half-strength glue. When thoroughly dry, apply full strength glue to the surface of the canvas, preferably just warm enough to be fluid. As it cools and gels, wipe your palm over the surface to equalize the application. Avoid saturating the canvas with full-strength glue solution - the first "drink" helps avoid that.

When the surplus glue cools, it will form a gel which can be frozen for later use, or refrigerated between uses for a couple of days. Do not use glue that is moldy, returned to a liquid while cold, or smells foul.

Some clarification. "Gesso" as we've come to know it in the 50 years or so since acrylic co-polymer artists materials have been commonly marketed bears no resemblance to the "real" gesso of the old masters, which is a compound of whiting, gypsum, and hide glue. It is too brittle for use as a painting ground on stretched canvas.

In general, acrylic primers are adequate to isolate natural fibers from oil absorption. Many painters feel the flexibility of an acrylic layer under oil paint is problematic for the longevity of a painting. (Violates the "fat over lean" rule.) Most preparations are quite abrasive, and really brutal on brushes.