Rabbit Skin Glue - do you need it?

[Mary Cupp]

Hello everyone,

I have been using modern acrylic gesso up until now, but decided that I should try the older methods. So I made a mixture of RSG for several recent canvases. Not having done this before, I realized (too late) that I had made the mixture too rich. The canvases look fine now. But I am concerned that the glue might run into problems this summer when the humidity is higher. I wonder if there is a danger of mold. Is this something I should be concerned about? Is there anything I could do at this point to prevent future problems? I am wondering how forgiving the mixture is if you don't do it perfectly. Does anyone have previous experience with working with glue.

P.S.
I plan to use a lead based ground (Holbein) before I start painting.

[Richard Bingham]

Mary, future problems with RSG have less to do with mold or varmints than what a too-thick application to raw canvas does. Too much glue is brittle, and that's not good under oil paint.

The primary purpose of the size is to isolate canvas fibers from absorbing oil, solvents, and vehicles in the paint. Ideally, a solution is about eleven tbsp. of dry glue to a quart of water. The quality and fineness of the dry glue is a factor.

First, cut that glue solution by half, to give the canvas a "drink". When that's dry, apply full-strength glue to the painting surface only. Hopefully the "drink" will keep the canvas from becoming saturated through and through with full-strength glue. When the solution starts to cool and gel on the surface, smooth it out with the palm of your hand. When dry, you may wish to lightly sand it with fine (220) sandpaper before applying the oil prime.

At this point, you'd be better off to wash the glue you've applied from the canvas (that can only improve things) and start over, so as not to have "overdone" the glue application. Hope this helps.

[Mary Cupp]

Thanks so much, Richard. I put the canvas under a stream of water and used a small scrub brush to remove as much glue as possible. I plan to let it sit awhile to soak the glue and repeat the process. How will I know when I have gotten enough off? I would imagine that the glue is inside the fibers and somewhat resistant.

[Richard Bingham]

Mary, if you use warm water, a couple of thorough washings should pretty well eliminate the glue. Really no way to tell if all the glue has been washed out, unless the canvas feels tacky when damp-dry.

[Mary Cupp]

Thanks Richard, You are a life saver.