Just wanted to ask if anyone knows if it's necessary to put gesso on illustration board before painting with oils on it. I would imagine so, since it's basically made of paper glued to cardboard, but I just wanted to be sure before I proceed.

The gesso is to prevent seepage of the paint into the board, no?

Thanks!

I have read of, and actually observed another Artist painting directly on Illustration board with oils. The board absorbs a portrion of the oil in the paint, and it had a flatter (less shiny) look than usual. I do not know the chemistry, but would guess that the binder is being absorbed to deeply into the painting and the paint film would consequently be weaker than one would hope for. Because of that I have stuck with priming both sides of the board and edges to initially get an even shrinking seal on the paper. As I said it has worked for me and held up well so far.Though I have done it (only twice), I'd personally sooner stick with canvas or panel though.

Perhaps someone else knows more of the scientific facts involved.

Carl

This about the paper absorbing the oil is true - but I have no idea if this will cause the paint film to be too weak. I have studied with realist/impressionist painters that sometimed put their paint on paper towels to have some of the oil absorbed before using the paint - this way one can controll the "fat" over "lean" rule when using paint straight out of the tubes without any mediums. But I think this also depends on what oilpaint it is - "student grade" paints might have more oils and less pigments than "artist grade" paints. It also depends on the pigment itself how much oil is needed to hold the pigments together. A good oil paint manufacturer will know this and you should also find out about this if makeing your own paints.