In some of my trompe l’oeil paintings the sides of the panel are part of the painting. Here is an example:
When I incorporate the sides of the panel as part of the painting, it requires preparation. The panels I like to use are either Ampersand Gessobord (museum series) or Ampersand Hardbord (museum series) panels. While the cradled “Gessobord” is factory primed, it lacks priming on its sides and the cradled “Hardbord” is unprimed altogether. Whether you prime the panel face, just the sides or both, it remains the same process.
Items I use:
Panel
Liquitex Professional Gesso (white)
Paintbrush
Scott paper towels
Sandpaper (grit 220, 320, 400)
Sandpaper holder
My process:
Step 1: I apply the gesso in a thin layer with a large flat brush finishing with brushstrokes in one direction. Let it dry.
Step 2: I apply another thin layer of gesso using the opposite directional brushstrokes. Let it dry.
Step 3: keep repeating the above process until there’s good coverage. Let it dry between layers.
Step 4: sand it using 220 grit sandpaper. Depending on how smooth I want my surface, I sometimes additionally gently sand my surface with 320 or 400 grit sandpaper too. The higher the grit number the smoother the surface will be. I like my surface fairly smooth but not completely smooth. Some of the brushstrokes will still be visible. Sanding has to be done carefully especially around the edges. If too much gesso is sanded off the panel, the wood gets exposed and more gesso has to be added.
Step 5: When done sanding I clean off all the dust.