How archival is oil painting on birch panels that are sized with a few coats of shellac? The panels are only 1/8inch thin and prone to warping as they are not cradled. Would shellac be alright to oil paint directly on top of if they were 1/4inch and cradled? If shellac isn’t archival can you recommend a way to prepare panels that gives a similar feel when applying paint?
can you expand on “slick coating”? We use several thin coats and then sand it to create a very smooth surface.
Shellac is not optimal but would work for the purpose you are suggest. It is essential to not create a slick coating and make sure that it is functioning as a size. The deterioration of shellac is probably less of an issue in the manner in which you are using it as it is completely hidden by subsequent opaque paint layers and is far less likely to suffer from vis light and UV degradation. Again, it is not a perfect solution, but will probably suffice if not applied to thinly or thickly. Shellac’s non-aqueous nature means that initial warping minimized. I would size both sides (and the edges to be thorough). One could substitute the acrylic resin B-72 (in xylene, acetone or ethanol/acetone mixture) for the shellac. Proper ventilation is necessary for these solvents. The B-72 would very likely behave similar to the shellac but it is a more stable resin. Again, this may be of a lesser issue when buried under layers of paint.
Slick as in reflective and mirror smooth. You really do NOT want that for your size layer as there should be enough mechanical “tooth” to the surface for the subsequent oil paint layers to successfully adhere.
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