Whether I am painting on paper, canvas or board, with oil and cold wax painting I always prepare the surface with at least two layers of Gesso as a tinted ground. This ground helps to further seal the surface layer to protect it from the paint application, and provides a tooth and absorbent layer for the paint to grip on to. It can also be made ultra smooth for fine paint application by using multiple layers of gesso that are then gently sanded until a really fine, smooth surface is achieved, or conversely can be made textured before the paint is applied using texture pastes or just by applying the gesso in increasingly thick and rough layers. I generally prefer a smoother surface but because I am painting in a loose, expressive manner I am not particularly careful how smooth the surface is at the gesso stage, using any resulting ‘imperfections’ to inform the painting story.
A coloured ground can also set the tone or mood of a painting as well as providing background interest where the coloured ground peeps through thin layers of paint or changes the colour of subsequent thin layers. It allows a better judgment of colour and tone as the paint is going on the surface. Depending on how dark or light the ground colour is, it can affect the mood of the painter and his/ her interaction with the painting as well as establishing the mood of the painting early on.
Generally I prefer a lighter ground to start off with and introduce the darks more as the painting progresses. After some experimentation in the past with different coloured grounds and some rather wilder initial layers I discovered that I also prefer cooler, bluer tones, or maybe a light raw sienna, starting off with a calmer layer, and introducing more expressive mark making later on as the painting makes itself known.