Tempered hardboard is a form of fiberboard. This engineered wood surface is often compared to particle board; however, it is much stronger and heavier than cheap particle board surfaces and tends to resist cracking and chipping much better. Paint won't permanently bond to bare tempered hardboard. To create a strong finish, you must apply a coat of bonding primer. If the hardboard is stained, it won't accept water-based primers. Be sure to choose the correct base, depending on the condition of the hardboard, or the finish will peel.
Wipe down the tempered hardboard with tack cloths.
Cover areas next to the hardboard, using tape. Use a low-tack painter's tape that will peel away without leaving adhesive residue.
Slide a dust sheet beneath the tempered hardboard. To prevent pooling and bleed-through, use a heavy-duty canvas dust sheet.
Coat the tempered hardboard with shellac primer, using a paintbrush with natural bristles. Shellac tends to run down vertical surfaces; be sure to smooth any drips before they have a chance to dry. Let the tempered hardboard dry for two hours.
Thoroughly rinse the paintbrush, using alcohol.
Coat the tempered hardboard with gloss latex paint or acrylic enamel, using a paintbrush equipped with polyester bristles. Smooth any flaws before they have a chance to dry. Let the tempered hardboard dry for two hours.
If the tempered hardboard is not stained, you may use an acrylic or latex primer; however, these coatings won't bond to stained hardboard.