Dear Moderators
Thank you for this wonderful website. So glad to see AMIEN has a successor.
I plan to paint on some RSG sized canvas and then (if the painting works out) to glue it to a rigid support. I had hoped to use my untempered Masonite as substrate to glue the textile to but recently read here that tempered is far better (however I don’t hold out much hope of getting that product here in Australia). I am very much aware of all the disadvantages of using RSG (have been reading about them for decades) but I strongly prefer the working qualities it imparts to the surface I paint on. Also I understand that RSG is much less problematic when used on a rigid support, if all precautions are taken (such as sizing and priming both sides and also varnishing both sides at the proper time etc). I had planned to just go ahead and glue the linen to the Masonite and then do the painting (much more straightforward) rather than size a stretched canvas, paint on it and then glue it on to the Masonite. However I can’t do this till I find a source of tempered Masonite. In the meantime I want to paint. My question is: is it unwise to use hot RSG to glue a finished painting to a substrate? Is it likely that the hot glue would damage the painting?
Thanks Brian, that’s very helpful.
If it is OK to use acrylic mediums to glue a finished painting done on RSG-sized linen to a panel, that actually solves a lot of problems for me. I had assumed there was some kind of incompatibility between RSG and acrylic based adhesives (gel medium is what I would use) which would preclude their use in this way. But if that’s not the case I’m very happy to hear it! Also I imagine that reducing my use of the RSG–by using it only as a size, while using an acrylic gel to seal the panel and glue the canvas on–would help to mitigate the bad effects of RSG. I am under the impression this mitigation of harm would be further enhanced by varnishing the picture, thus reducing the possibility of moisture penetrating and triggering the hygroscopic behaviour of the RSG. Would you agree that overall this would constitute “harm minimisation”?
Absolutely clear on that. I will only use RSG to size the linen. All other sealing and gluing will be done with acrylic dispersion mediums On the strength of your advice, I’ve decided to scrap the idea of gluing the finished painting onto the panel and will instead just go for the safer and more straightforward option of sizing on a stretcher then removing the textile and gluing it to the panel BEFORE painting. Thanks again for helping me develop a sounder (and less messy) procedure.
hello again Sorry to bring up yet another question but given the suggestion of using acrylic medium to attach my pre-RSG sized canvas to a panel, my new question is: Would it be within the bounds of reason to save even more time and just go directly to gluing the canvas to the panel using the acrylic “glue” and then (once the glue has dried and cured–maybe after a week) simply size the now-attached canvas with RSG? I do realise none of this is optimal. Perhaps we might call it something like harm reduction for someone who wants to use RSG as a size for her canvas (to test out a theory that it produces a nicer surface for working on). Any thoughts you have would be very welcome. Thanks for your patience!
We are very happy that you find the site useful. It is true that the conservation field would like to persuade artists from using RSG because of all of the issues you are well aware of. I also understand the reluctance of some artists to abandon this material due to the qualities it imparts to stretched canvases.
So let’s ignore those issues for the moment and focus on the suitability of using animal glue to adhere a finished painting to a rigid support. First, as you suggest, it is far preferable to adhere the canvas to the support before painting. You know this as well, so let’s move on. In the situation you outline, I would strongly suggest that you use an acrylic dispersion medium or gel in place of the RSG. It is less likely to cause issues in the canvas while drying and creates a far better bond. Animal glues are very strong and have great adhesiveness but are poor gap fillers. When gluing canvas to a rigid surface, it is generally far better to use an adhesive that good cohesion and fills the interstices of the reverse of the fabric rather than an adhesive that has amazing adhesive strength but is a poor gap filler. We do cover this subject to some degree in our RESOURCES section under Rigid Supports.
When possible, it is preferable to avoid introducing moisture to a completed painting or one that contains an animal glue size. Water added at this point may cause uneven buckling. This is not always possible and is one of the reasons why it is best to completely prepare the canvas/panel substrate before painting. You could possibly use a thermoplastic heat-activated adhesive like BEVA 371 as well but that would depend on the surface texture of your painting and the degree of impasto. I also suggest that you allow the painting to dry for some time before even thinking about applying heat to the surface. Again, you can read more about this in our Rigid Supports PDF.
To be perfectly clear from the begining, this procedure is not optimal, as you already mentioned.
I think that the answer to your questions is yes. Just to be sure we are on the same page, I would not suggest sizing the hardboard panel with animal skin glue and then use acrylic dispersion medium for adhering canvas. This may cause problems as well and there would be possible incompatibility (or at least solubility and dry time problems and issues). In place of this you could size each size of the panel with the acrylic dispersion medium and then adhere the rsg sized primed and painted canvas to this panel using the acrylic dispersion medium. Done carefully, this should work fine, or certainly as well or better than the using rsg to glue the canvas.
On the final though, varnish will likely slow down the penetration of moisture into the stratigraphy but it would not really stop it. If this were the case, the hygroscopic nature of animal glue would be not issue at all when used on panel paintings. A final word of caution, though. Care needs to be taken to restrict unrestrained movement of the canvas (weighing, etc) to prevent any subsequent shrinking during the process (this is why we always suggest adhering the canvas to panel before painting) to prevent damage to the ground and painted surface.
We would not advise going this route however we are also not 100% positive that it wouldnt be fine in the long run either (as long as you document what you choose to use on the back). One concern would be that in places where the acrylic has seeped through the canvas weave, the RSG might not adhere well to these areas. Conversely, the canvas could also become less absorbent overall, therefore making your RSG layer function more like a coating (which is more problematic) rather than a size layer.
