Gel stain is formulated more like paint than traditional stain. Like paint, gel stain coats the surface instead of penetrating it. It's primarily used on wood, although it can be used on other surfaces, including fiberglass and metal. Gel stain is also used for faux finishing and glazing. You can paint over gel stain as long as the surface is free of peeling stain or varnish, and it is sanded and primed.
Painting Exterior Surfaces
Gel stain has to be varnished when used on exterior surfaces. Therefore, preparation must include scraping and sanding, both to remove loose or peeling stain and varnish, and to dull the varnish. Priming and painting directly over glossy varnish almost guarantees poor adhesion, and the paint will start peeling or chipping.
Use mild detergent and a sponge or soft scrub brush to remove oil and grime. Clean corners and scroll work on doors or stained furniture with a toothbrush. Rinse and let dry. A scraper or putty knife will come in handy for removing loose gel stain and varnish, and sanding sponges do an excellent job of reaching nooks and crannies, or sanding uneven surfaces.
Prime with an alkyd (oil-based) or latex stain-blocking primer. Don't use tinted shellac primer on exterior varnished surfaces; use alkyd primer instead. Apply two coats of primer to heavily weathered areas, and allow it to dry according to label directions. Two coats of good quality paint hold up better than one outside. Even if whatever you're painting looks fine with just one coat, do a second for maximum durability, using 100 percent acrylic (water-based) paint or. Oil-based paint can work fine for metal or fiberglass, although it takes a lot longer to dry.
Painting Interior Surfaces
Since gel stain is very heavy-bodied and much less likely to spatter and drip during application, it's often used on vertical interior surfaces such as paneling, cabinets and doors. When used inside, it doesn't need to be varnished, although in most cases it is--unvarnished, stained wood is not easy to clean and can look a bit dull. The same procedure applies to interior surfaces as exterior ones. They need to be free of peeling paint and grime, sanded until dull and primed before painting. Stain blocking latex, tinted shellac or alkyd primers all work well on interior surfaces. Keep in mind that shellac and alkyd primers have very strong fumes and require mineral spirits for cleaning up.
Use any good quality interior paint once the primer has dried. It's fine to paint over oil-based primer with latex (water-based) paint—it's only oil-based paints that shouldn't be painted over with latex. If you're painting something intricate like furniture, you can even use paint in spray cans for the entire project. Just be sure to read the label directions—some spray can paint doesn't require priming, but if it's lacquer-based you can't use it over many stains and varnishes. It's a good idea to read paint label directions no matter what--there are so many different formulations on the market, and many require different procedures.