I've been doing some research on preparing wood surfaces for oil paint, and I am finding lots of conflicting information. I have a giant piece of 1/2 inch birch plywood that I want to cut down into several 18x24 panels. I have two questions: Do I need to create supports/cradles on the back to prevent warping, or is 1/2in thick enough that it shouldn't be a problem at an 18x24 scale? Also, What should I use to prime the boards?
I haven't found much good information on DIY cradling. I would probably cut bracers to go around the back, with 45 degree edges, and glue and clamp them down. I've heard that gluing isn't exactly the most archival method of creating cradles, but I haven't heard any other good options that are really DIY friendly. Does anyone have any opinions on what kind of glue I should use?
Here's the tricky part: I want the wood grain to show through, so I don't want to use an oil ground or acrylic gesso, because that kind of defeats the purpose of painting on wood in my case. (I want the surface to kind of look like Audrey Kawasaki's paintings, where the wood is an element of the painting). I've heard that I can do this with Gel Medium or PVA sizing, but I'm not sure if the PVA sizing is archival. Does anyone have any advice? What is a good number of coats to put down?
PVA is archival and acts an awful lot like Liquitex Gel Medium (at least they seem to be the same thing to me). Gluing your cradle/stretcher bars should be just fine - not going to be anywhere near your paint surface anyway. Half inch is pretty hefty for 18x24 - but couldn't hurt to brace against warping anyway - plus makes it a lot easier to hang.
What would Caravaggio do?
I paint on gessoed masonite panels that are 1/4" thickness and have gone up
too 40"x48" (which is pretty heavy in weight) with no cradling so using 1/2" plywood
so you should not have to worry about supports. Framing is going to be the issue
with the thickness. You need to decided how you are going to frame your work
adding supports will add more weight unless you are going to use the supports
to hang from. I have a friend that uses the same plywood and she gessos her 1/2"
panels and paints in oils (with no cradling) and uses custom frames because of
the 1/2" depth in thickness of the panels. So I think you be fine.