Rabbit Skin Glue - do you need it?

[Richard Bingham]

Claudemir, the common objections of cost, and expenditures of time (better spendi it painting, instead of making supports) are certainly valid.

Anyone who preps their own supports simply to save money is definitely barking up the wrong tree, but I assure you that for my own purposes, neither Claessens nor Fredrix provide what I make up in my own studio. As they say on TV, "Not sold in stores!!"How important is that ? Not very in the long haul, probably, but it assuages my need to be totally in control of the process.

The unfortunate thing is that discussing the process online is bound to annoy some folks who prefer certain approaches or materials over others, and will not be thoroughly helpful to those trying to learn how, because although it's not rocket science, it's involved enough that the only good way to instruct a sound method for stretching and priming canvas is to see it done beginning to end.

Thomasin, the variables you indicate make it a real problem to answer your questions. That said, making the linen "drum tight" is not the purpose of sizing, and glue in too heavy a concentration, improperly applied is likely to cause problems. Not having ever used a microwave to warm glue size, I can only speculate that as microwave is known to change the consistency and character of many foods, it may or may not be advisable to use making glue.

Tensioning of the fabric through shrinking or stretching is an issue entirely aside from sizing. Coating or saturating the fabric with a heavy concentration of glue size is inadvisable. Think of the glue as being like a sheet of glass between the paint (and its oils) and the fabric. It is a barrier. The half-strength "drink" is applied to make it so a full-strength application will not saturate the linen, but remain on the painting surface as a barrier coating. One application is adequate if properly applied.

Now I'm confused. "PVC" may be understood to stand for Poly Vinyl Chloride, which is a plastic. House paints of any species have no place in the preparation of a fine-art painting support.

If you intend to use a water-reducible acrylic co-polymer "gesso" to prime a canvas, there is no need to use RSG at all.

[Marina Dieul]

Thomasin,
I don't know what is a double boiler, but here is the traditional way I learned to heat the RSG : in french it's called " au bain-marie". You don't need to make the water boil, the RSG souldn't exceed 60 celsius degres, or it will loose it's qualitys.

[Richard Bingham]

Marina, thanks for posting that picture. That's exactly the kind of "high-tech" double boiler I've always used . . . If hot water from the tap is at least 150F, that's adequately hot to liquify RSG that has cooled to a gel, using the "system" pictured.

[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.