If you plan to paint a stone fireplace, consider some fundamental points before you get started. Unlike wood, stone is nonporous. Hard, nonporous surfaces are not suited for new finishes. Before you paint, condition the stone with a bonding primer, or the new finish coat will eventually peel. Prime and paint the fireplace, using the right technique, or you may end up with noticeable skip marks within the porous mortar between the stone.
Use a plastic brush to wash the stone fireplace with soap. Rinse the stones with wet rags. Allow a minimum of four hours drying time.
Shield areas adjacent to the fireplace by covering them with tape specifically manufactured for painting projects. Shield the ground beneath the fireplace, using dust sheets.
Coat the stones with latex primer, using a nylon brush. Brush vertically, being careful to work primer into the mortar between each rock. Dab the brush against the mortar to fill the tiny pores. Allow the stones to dry for two hours.
Wash each painting instrument with water.
Paint the stone fireplace. Use semigloss or gloss latex paint. Allow the stones to dry for two hours.
Never paint a bare stone fireplace, or peeling will result. Do not prime or paint a stone fireplace, using a polyester paintbrush. Don't use a roller on a stone fireplace, or the paint may run.