In researching how to prepare hardboard for painting you will find many versions on the theme but here’s the method I use.
- buy tempered hardboard 3/16” in width. Home Depot will cut if to size. Keep the off cuts too.
FYI tempered hardboard was given a bad rap for years because of the use of oils in the manufacturing process, which caused problems with paint not adhering to the surface. In recent decades the manufacturing process had changed and there is little difference with the oil content between tempered and untempered. However to safeguard against any chance of yellowing with time I seal both sides of the hardboard as part of my preparation.
- seal both sides with water-base polyurethane varnish on BOTH sides (some people don’t do this but rather use many coats of gesso. I varnish AND gesso with 3 or 4 coats:)
- lightly sand the smooth side. I use 220 sandpaper.
- glue and nail wood to the back to keep it rigid. I sometimes use 1/2 x 3/4 pine. You’ll find it on the aisle with the wood moldings. I use wood glue and clamp the wood to the rough (back) side of the board then nail it with #18 Wire Brads (small nails). Make sure the nails are completely flush so they don’t show through the gesso.
- make corners from the off cuts of hardboard to nail to the back corners to keep the panel rigid and flat
- 3 or 4 coats of gesso, fine sanding between coats. brush horizontally, let dry, sand, then brush vertically, let dry, sand etc
DONE! Happy painting everyone!