With the right coatings system, you can apply paint to virtually any surface in your home. The biggest challenge to painting over a clear polyurethane or other varnished surface is adhesion, because most house paints are formulated to bond onto porous surfaces such as wood, plaster and drywall. When you select the correct primer and topcoat, however, you can finish your project quickly with minimal surface prep.
Overcoming Adhesion Challenges
Polyurethane clear coats repel water, grease and dirt to protect the surface beneath. Clear coats make routine housecleaning simple because you can wipe off grime and oily fingerprints using household cleaning sprays and a damp paper towel. When you decide to apply paint to a clear coat, however, you'll find house paints are not engineered for adhesion to slick, non-absorbent substrates.
Simple Surface Prep
Gain a better foothold for your primer and paint system. Clean the clear coat with trisodium phosphate or an environmentally sensitive alternative labeled as a TSP substitute. Either cleanser gently de-glosses the clear coat and lightly etches the surface for adhesion. Wipe on a TSP solution, then allow it to sit for about five minutes before rinsing it off. If you apply the right primer for the job, this is all the surface prep you need.
Primers That Grip
While an all-purpose primer is sufficient for ordinary purposes, you need a primer with special characteristics to grip onto a shiny surface such as a clear sealant coat. Bonding primers are formulated with a higher binder content to enhance adhesion onto slick substrates. Once it's fully dry -- typically two hours or less -- the bonding primer serves as an effective undercoat for virtually any paint of your choice.
A glossy or semi-gloss acrylic latex paint can best approximate the performance of the clear coat. A 100-percent acrylic latex paint forms a tougher protective shield for your surface in terms of water resistance, impact resistance and abrasion resistance. In addition, these premium-grade paints usually boast fade-resistant colors. Like the original clear coat, a glossy or semi-gloss painted surface more easily can be wiped clean with a damp cloth and if necessary, you can safely use most household cleaning products.
Mike Matthews is editor of Green Building Product News, a national publication that covers sustainable innovations in building and remodeling, and he has spoken at national conferences on green building. He has also served as founding editor of "Paint Dealer" magazine.