Varnish is a type of sealant that is typically used on wood fixtures, cabinets and doors in homes. Over time, varnish can become worn and sun damaged, especially with front doors. One way to fix this issue is by painting over the varnished woodwork with an acrylic or oil-based paint. The woodwork must be cleaned and prepared before beginning the painting process. Otherwise, the beautiful paint job will not adhere to the surface and will chip easily.
Remove the door from its hinges. Do this with a screwdriver and the assistance of someone holding the door so it does not fall in the process. Remove any hardware such as doorknobs or handles.
Clean the door with an all-purpose cleaner to remove furniture polish and greasy build-up. Use a textured cleaning pad to rub the cleaner into the surface, which will also help bring down the glossiness of the varnish.
Sand the door lightly using a medium-grit sandpaper. Sanding will create a "tooth" on the surface, which will make the primer stick and expose grease-free varnish underneath. Wear a face mask when sanding varnish. Sanding down all the way to the wood is not necessary.
Vacuum the dust left over from sanding. Soak a rag in a solvent like denatured alcohol or mineral spirit and rub the door down. Use white spirit if the varnish and primer being used are oil-based.
Pour either alkyd (oil-based) primer or acrylic (water-based) primer into the paint tray. Use alkyd primer for oil-based varnishes and acrylic primer for water-based varnishes. Brush or roll the primer onto the door surface. Two coats may be needed. Refer to the directions on the primer container for coating recommendations. Let dry.
Apply one or two coats of acrylic or oil-based paint until fully covered. Make sure the paint type coordinates with the varnish and primer type (water- or oil-based) for proper adhesion. Also, use outdoor paint for front doors and indoor paint for interior doors. Let dry. Have someone help hold the door in place and use the screwdriver to reattach the hinges.
Hang solvent-soaked rags outside to dry, away from flammable surfaces. Solvents are extremely flammable.