Though you may use any kind of paint on a rock surface, some types provide greater durability in certain situations. Learn which paints last best on rock and which tend to fade, flake and crack. Remember that, if you don't prepare the rock in the correct fashion, finish failure will result regardless of the type of paint you choose.
No type of paint will bond to a bare rock surface. If you roll, brush or spray a coat of paint directly over the top of rock, the finish may appear uniform and durable at first glance; however, after a short period of time, flaking will result. To promote a lasting finish, thoroughly clean the rock to eliminate dust and oils. Use soap and a coarse plastic brush to clean interior rock surfaces. Use concentrated water pressure from a pressure washer on exterior rock. Once the rock is clean, apply an enduring primer. Latex primer is fine for rock subject to little duress, such as rock veneer and rock fireplaces; however, it may fail on surfaces subject to weather and friction. For exterior rock surfaces, rock patios and floors, use an acrylic primer.
Latex paint works well on rock surfaces forced to endure little duress. Use an eggshell, satin or semigloss paint on interior rock veneer and rock fireplaces. Remember that the more sheen the paint has, the easier it will be to clean.
Acrylic paint is appropriate for exterior rock surfaces, such as rock walls and siding. This paint has great flexibility and can expand and contract as temperatures warm and cool. Ordinary latex paint is not fit for exterior rock surfaces, because it is not resistant to harsh weather and UV rays.
Epoxy and Acrylic Porch Paint
Horizontal rock surfaces that lie underfoot, such as porches and walkways, require durable paints able to withstand significant duress. Use either an epoxy or acrylic floor paint on these surfaces, or you may end up with fading, cracking and/or chipping. Acrylic porch paint is best-suited for exterior horizontal rock surfaces, because it won't fade in the sun. Epoxy is best for interior horizontal rock surfaces and is not resistant to UV rays.
Acrylic enamel is well-suited for small decorative rocks. It offers an attractive sheen and is able to endure consistent handling, harsh weather and sunlight.