I have two questions regarding my particular case of preparing cradled plywood panels for egg tempera painting
1. Will traditional RSG and/or RSG gesso adhere to a panel that has been sprayed or brushed with Shellac?
2. Is it reasonable to seal a plywood panel with Shellac to keep moisture out and then use that panel with traditional RSG and/or gesso? From my research and experience it is common to simply size wooden panels with RSG first, and then continue to apply RSG gesso. However given the hygroscopic nature of both the wood and RSG, wouldn’t sealing with Shellac first at least help reduce movement and other problems caused by moisture? The panel manufacturers I have been talking to in New York certainly encourage sealing panels with Shellac but the majority of their customers are working with acrylic and oils, not traditional gesso and egg tempera. What do you think?
Thank you, I love this forum btw!
Eli
Eli Bornowsky
Thanks for your prompt response Brian! What would be the case for sealing the back of the panel first vs after besides the risk of getting stuff you don’t want on the front of the finished painting by accident?
I use panels, which I unforunately sealed with shellac (to protect a drawing) and I have started using gesso on this surface to help adherance of mixed media work. I found that regular gesso (clear gesso by liquitex) had no problem adhering to the shellac surface, and I have had no evidence or threat of delamination or separation etc… I have not used RSG gesso, though. I plan to stop using shellac on future panels though.
Sealing with shellac is fine under an oil ground but I would not suggest applying shellac to the surface of a panel that will receive a glue bound ground. It would only cut adhesion and make the failure of the ground more likely. It would be fine to seal the edges and back with shellac but I would probably do that after completing the painting (a case could be made to do it first as well).
I like to apply sizing and at least some gesso to the back of the panel, if it is not very small, to diminish warping so I would seal after. Not getting shellac on the paint on the front is a reason for doing it first. You could always sand off anything that got on the front of the panel before sizing and applying your ground.
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