What Kind of Paint to Use on Indoor Faux Cement Fireplace Rocks?

Investigate First

• Determine what type of stone facing you have on your fireplace before attempting to cover it with paint. Chip your fireplace facing in an inconspicuous place to take a sample to determine the composition and porosity of your stone. Several materials have been used over the years to make less expensive, lighter-weight, rock-like walls and fireplace surrounds. Real stones, sculpted with diamond saws, lose half or more of their weight. Cultured stone combines crushed stone and cement, and whipped cement contains polyurethane. Both use molds to create realistic shapes that are dyed either before or after the materials are mixed. Cultured stones, peppered with mica, feldspar and other twinkly minerals, approximate the look of granite or other expensive stone.

To Seal or Not To Seal

• Some fireplace face rock is made of concrete that is literally whipped to fill it with air. This material is full of tiny air bubbles that absorb buckets of paint -- especially if you choose to use latex paint or a cement dye to simply change the color of the rocks. Latex primers are labeled for use on stone, and latex paints may have bits of sand or mica in them to mimic a stone surface. Oil-based or acrylic paints contain enough body to form a skin on the surface of the stone with the first coat and seldom need sealant or primer.

Before You Paint

• No matter what the container says, clean the stone thoroughly before applying any paint to fireplace stones. Dust and dirt work into stone surfaces and cause peeling when paint is applied over them. Fire soot contains not only carbon but grease from wood sap and prevents paint adhesion. Check the stone product for pH, the degree of acidity or alkalinity. Paints that are formulated for wallboard or wood surfaces work well with a neutral to slightly acidic surface, and cement can be alkaline. Paints that are formulated for cement are balanced to compensate for this difference. Others may cause cement stones to de-laminate and chip.

Application

• After cleaning and applying any required primer, lay on the cement paint in several thin coats; one thick coat traps the moisture in the facing and will peel. Use a roller for flat stones and a brush to apply paint to uneven surfaces. Paint without texturizing additives may be diluted with water or paint thinner and applied with a sprayer; read the package directions carefully for thinning guidelines. Use a thick, stiff-bristled or stencil brush to stipple the top coat, creating the uneven appearance of stone. Allow each coat to dry thoroughly to draw as much moisture as possible from the stone and each paint layer.