Résumé : Paintings come about from the encounter between substances.This text will describe painting on unprimed canvas – canvas in which the fabric has not been covered in preparatory layers – as an encounter between fabric and paint. Oil, egg, solvent, glue, pigment, resin and water interact withcotton, linen or hemp fibers woven into what – uncovered –can constitute a reactive membrane for paint instead of a mere support. Painting’s materials are subjected to forcesduring the process of making, and for the rest of their lives: forces of push and pull due to phenomena like gravity, capillarity, drag, attraction or repulsion.The thesis calls attention to some of the possibilities and drawbacks that this encounter produces for the painter, and what it does for the viewer. What does the unprimed canvas enable, and what does it produce? How does the raw fabric of the unprimed canvas function inside the pictorial space, for the painter; and how then does this impact the perception of that pictorial space, by the viewer?