Q. Ive been doing a lot of plein air painting on pieces of canvas stapled to 1/2-inch thick foam board. Now I want to mount them on hardboard panels and then trim the edges. Does the panel need to be primed before I apply the adhesive? What would be the best adhesive to use for attaching the canvas to the boards?
A. I dont think the hardboard panels need to be primed (that is, coated with a ground), but it might be a good idea to seal them with a sizing before mounting the fabric. First, lightly sand the panels surface all over. Then youll need to dust it thoroughly. For the sizing, you can use a pH-neutral PVA size, or an acrylic dispersion medium like Golden Artists Colors GAC 100 or GAC 700. Its a good idea to coat both sides of the panel and its edges with a thin layer of the sizing material; if you put sizing on only one side, the panel might warp. Then allow the sized panel to dry at least overnight.
I favor using an acrylic gel medium for the mounting adhesive because the gel mediums dont dry as fast as the regular mediums, giving you time to make adjustments to your piece. Spread it on the panel in a thin layer. You can apply it with a spatula or palette knife and then smooth it with a large brush dampened with water.
Put the painting on the panel and smooth it with your clean fingers so there arent any wrinkles or air bubbles. The gel mediums slower drying time will allow you to reposition the picture if you make a mistake. To be sure that the painting surface has a firm attachment to the board, you may want to roll the surface with a soft rubber brayer, starting from the center and moving out toward the edges.
Be forewarned, however, that the brayer may flatten or break the peaks off any impasto brushstrokes in your painting. (I like to mount my paintings, too, but because I have thick areas of paint in my pictures, I avoid the risk of flattening them by mounting my canvas onto a panel before I paint.) Allow the gel medium sufficient drying time, and then trim around all the edges.
Ross Merrill is chief of conservation at the National Gallery of Art in Washington, D.C.