Preparing Hardbord™ with Oil Primer and Acrylic Gesso

Ampersand Hardbord™ is an excellent substrate for panel painting. If sealed correctly, Ampersand Hardbord™ can be a better substrate to use than a birch plywood or mahogany panel because it is not subject to expansion and contraction as it absorbs moisture. Ampersand Hardbord™ is made by permanently binding wood fibers under extreme heat and pressure. The result is an extremely hard, grainless panel of uniform thickness and density that offers a dimensional stability not found in natural wood panels.
Following are the basic instructions for either oil priming or gesso priming your Ampersand Hardbord™.

 
Oil Priming
1. Sizing the Panel
A size is a thin solution (often a weak glue) which is brushed directly onto the support. Sizing is necessary to protect Ampersand Hardbord™ from any harmful oil absorption from the priming and paint layers. The linseed oils used in some primers and oil paints can lead to a slow disintegration over time if the wood is not sized before applying the ground. You may use traditional hide glue, a PVA size, or a matte gel medium to size your Ampersand Hardbord™. (Note: To avoid having to size your panels and to speed up drying time, you can use the Oil Painting Ground manufactured by Gamblin Artists Colors. It is an alkyd based ground that dries within a matter of days. It may be applied with the same technique used for traditional oil primers described in steps 3 and 4 below.)
Sand and dust the panel. Bevel the edges if desired. Apply the sizing thinly. The edges and the back of the panel should also be covered to retard moisture penetration and equalize shrinkage and stress on both faces of the panel. When the first coat is dry, apply a second coat to fill any pinholes that may have been left after the first application. Make sure that the size is evenly distributed over the entire face of the panel without leaving any glossy areas.
2. Preparing the primer
A number of pre-made oil primers are available. Generally they are made up of a white pigment, linseed oil and driers or solvents. Other primers that use alkyd resin binder instead of linseed oil dry faster and are non-yellowing and more flexible than traditional grounds. Both may be applied in the same manner with either a large trowel shaped knife or a large stiff bristle brush. Thin the traditional oil primer with lean gum turpentine to a workable consistency enabling easy application over the sized panel. Never add oil to a primer. Its leanness must always be preserved. Begin by mixing small amounts of turpentine with the primer. You can test the right consistency by picking up the paint with a knife and shaking it gently. If it falls from the knife, it is ready to use.
3. Applying the Primer
When priming with a palette knife, begin by placing a portion of the primer in the center of the panel. Spread it in one direction and then in the opposite and in a diagonal direction. Prime the edges of the sized panel. The second white priming can be applied the next day or any time after the priming has dried. This will somewhat reduce the texture of the panel. If priming with a bristle brush, use a large bristle brush size 12-24 and apply the primer by stroking the brush in a wiggly-waggly motion, working it well into the surface. After evenly distributing the primer over the whole surface, finish by going over lightly with a clean brush carefully in straight lines. At least 2 coats of primer should be applied.
4. To Finish
Eliminate any unevenness by lightly sanding the panel after it has thoroughly dried. The oil priming should dry a minimum of 10-14 days at normal room temperature before painting. If you prepare several panels at a time then you will have stock on hand that is dry and ready to paint when needed.
 
Acrylic Gesso Priming On Hardbord
Lightly sand Ampersand Hardbord™ to roughen surface for better adhesion of gesso to the panel. No sizing is needed when using acrylic gesso because it is a size-and-ground combination. First thin acrylic gesso with up to 1/3 water for the first priming so that the gesso can flow more easily onto the panel. Begin by moistening the brush with water. Work the brush back and forth in one direction and then in a cross direction with a little pressure so that the gesso can better penetrate the panel. Apply gesso to the sides of the panel to protect it from accidental contact with any oil paint. After the first priming, some roughness may need to be smoothed out with light grade sandpaper. The second priming of acrylic gesso does not need to be thinned with water. Apply it as the first. Sand again and keep applying layers of gesso until you have reached the surface desired. A toned ground can be made by tinting the gesso with an acrylic paint.