what are the preparatory layers of a painting?

Answer 1

First primer like gesso and then underpainting and then paint.

Answer 2

I have studied art all my life and while there are many ways of laying down gesso...from one layer to 100...there are no "preparatory layers" required other than priming. In acrylics, you can bypass gesso and paint on raw canvas if you like the effect. Jackson Pollock used oil-based house paint, enamel..whatever right on raw canvas. If you're a Sunday painter, you might want to "do things right" and use multiple coats of thinned gesso, sanding the nubs in between ever so lightly. I suggest if you really want to learn to paint, that you concentrate on producing 100 or so paintings before you worry too much about archival processes. The early stuff should get thrown out -- or repainted -- anyway.

Answer 3

answerguru puts it succinctly and eloquently. Perhaps you might add drawing, preparatory sketches and underdrawing (though many go straight in with paint).