Gesso Panel Part 4: Bracing the BackMarch 2, 2011
The final step in this project is to add a brace to the back that will help keep a thin panel like this as straight as possible.
I’m using ¾ inch (20mm) square strips of poplar, which is a hardwood species that takes glue well and has low shrinkage. The panel is 12×16” so I’m placing two strips along the 16” length (horizontal) and three along the 12” length. The intersection is a half-lap joint cut on a tablesaw. This notch is cut with the blade set to half the height of the strip and ¾ inches wide. You can use a dado blade attachment or just whittle it across with a single blade. A router would make short work of this also.
The brace is glued to the back by placing 1 inch spots of glue at each end and about 1 inch apart instead of all the way down. This allows the wood to have a little more “give” but still be held straight; otherwise, you might see a ridge puff up on the front of a panel this thin. The glue I’m using is PVA wood glue. Once it’s in place, I put some weight on it and let it dry for a few hours. The panel is now ready for painting. The brace makes the whole panel as deep as a stretched canvas, and can be framed accordingly.
Although this whole gesso project may seem long and laborious, the only time you need to be careful is to use the right temperature for the glue and to use caution when applying the layers. Consider that an acrylic dispersion “gesso” must properly dry out for several days before painting on it with oils, and an oil primer takes several months to cure. This whole project took me about 4 days from start to finish (less time would have passed if I didn’t bother using fabric,) and most of that time was spent just waiting for the glue to dry. If you want to try out the surface on commercially prepared gesso panels, check out companies like Real Gesso or True Gesso.