I have heard people saying that oil will "rot" the paper if a sketch is executed in oil on paper without first sealing the paper. I'm not quite sure of the biochemistry of this, as I would have thought that the oxidised oil would act as a protective sealant for the paper fibres ...
The question I ask this, is because of advice given by Roger de Piles on landscape sketching on paper, where he says,
"Others have painted on strong paper of medium tint, and have found the method convenient, in that the absorption of the colours by the paper makes it easy to put colour over colour, even if different, one from another" (Cours de peinture par principes, 1708)
This would mean not sealing the paper, I assume, as this would defeat that objective. I assume that this method does not damage the paper, as so many of these sketches still survive, and almost all the landscape sketches carried out in the 1700's through to the late 1800's appear to be have been made on paper, or cardboard. Artists who painted landscape sketches on paper include:
Bidauld, Blechen, Bertin, Bonington, Böcklin, Belmont, Burkel, Buttura, Camuccini, Cels, Closson, Cogniet, Corot, Closson, Constantin, Denis, d'Aligny, von Dillis, Fleury, Fries, Giroux, Granet, Heydeck, Knip, Michallon, Nerly, Reinhold, Remond, Rottmann, Schelfhout, Valenciennes, ... et cetera.
Does anyone here practice landscape sketching on unsealed paper? I assume that packing the sketches between layers of greaseproof paper, once the surface is no longer tacky, will protect them until the oil is totally oxidised, or simply tape them to the wall until they dry?
I have only ever painted in oil of paper sealed with shellac (50g button shellac dissolved in 500ml of methylated spirits is how I prepare it). This is slightly absorbent, which I like, as it means that I can paint a second layer of colour much more quickly than would be possible if I were to paint on a fully sealed surface.
-Evan.
