"River Birch Trunk", Pastel and Charcoal on plywood, 8"Tx10"W, 2014/02/08
by John Terwilliger
Plywood is not a very forgiving surface to draw on with dry media. Most of the drawing material does not stick to the surface when applied and more blows off when using fixative. This gives itself over to a dramatic change in the drawing when fixed that takes a little fore-site into the final results.
The best results on plywood are from graphite and charcoal. And with charcoal the compressed charcoal works best as it has a higher wax/oil content then vine or charcoal pencil. Soft pastels have virtually no binder in them and rely on the substrate (usually paper) to hold them in place and plywood is not very friendly that way.
I do not use oil pastels much so will not comment beyond the fact that the pastel stays put and does not need fixing. However the oil will soak into and spread out on the surface darkening and discoloring the wood.
All of the various plywood types become darker when you spray fix the drawing. If you do a final varnish coat it darkens by several shades. This is not surprising to anyone who has ever refinished furniture it is the nature of raw wood and varnish. It is something to plan for and enhances the wood grain pattern which is the reason to use plywood in the first place.
You do need to spray fix the work prior to varnishing or the liquid varnish with wash out the drawing, even when using a spray varnish. I use a workable fixative first, as this gives the wood a little “tooth” for the varnish to adhere to. Then I use a spray varnish that is rated as crystal clear. Most varnish for wood has an amber hue to it and again will darken the drawing. If that is what you want you can use it.
When doing countertops or tabletops I use high wear professional floor varnish. Several coats of that following the manufacturers instructions, wait seven days for a full cure, and you have a surface as durable a hardwood floor.
If you choose not varnish or fix the drawing on plywood it needs to be framed with glazing (glass or plexi-glass). When putting dry material behind glazing it needs to be spaced back from the glass. With regular glass the space of standard mat board is enough. With plex or acrylic you need about a ¾” gap to keep the drawing material from leaping up to the plex due to static electricity.
As with anything a little care and planning and make a world of difference in the final product.