Critique for da CriticGod
Join Date: Aug 2010
Location: Philadelphia, PA USA
I think 3/8th inch or 1/2 inch thick foam core is the way to go. The normal presentation board weight is too thin. 1/4 inch or thinner looks fine but as you paint it and apply water based glue it has a tendency to warp. The danger is how the outer paper layers react to the water in the paint and the paint itself. The paper will often expands while soaking up the water, paint, or glue and then contact as it dries - sometimes more than it expanded because of the binders in the paint.
I would recommend coating the foam core with spackle or wall/joint compound. A spackle knife should be suitable for this. If done sparingly this creates a pretty good concrete texture, and creates a good foundation for paint.
After the spackle dries I would recommend a coat of artist gesso mixed with pva glue. Gesso is primer for artist canvases, it stiffens and seals the canvas. The pva glue also adds a hardness to the gesso when it dries. The mix should be mostly gesso . . . Somewhere less than 1/8th glue to 7/8 parts gesso.
I hope that helps!