How to Paint a Cast Stone Fireplace

What You'll Need
Protective mask and gloves
Dust brushes
Dish detergent
Bucket of water
Stone cleaner (orthophosphoric acid)
Masonry primer
Oil based paint
Stone sealer
Clean pieces of cloth
Old newspapers

A cast stone fireplace may be the centerpiece of a living room. Cast stone fireplaces are made up of cement, sand and other stone chips that are mixed and cast into a shape. These types of fireplaces are less pricey than natural stone or brick fireplaces, and are also easy to install and paint. Sealing the cast stone is essential, as the porous surface and will otherwise be prone to staining and gathering dirt.

Step 1 – Clean the Fireplace

Remove the dust and soot with a piece of cloth and dust brushes. Wear a mask to make sure you don't inhale various harmful particles. Wash the cast stone fireplace with warm water and dish detergent. Allow the surface to dry. If you find persistent stains, clean the fireplace with orthophosphoric acid, which is ideal for stone and cast stone cleaning and may also eliminate rust. Make sure you use only diluted solutions of orthophosphoric acid (the concentration of acid should be less than 5 percent). Wear rubber gloves to protect your skin from the acid and apply the solution on the fireplace. Allow it to set in for five minutes.

Step 2 – Rinse and Dry

Rinse the acidic solution, making sure to remove all traces of acid. If you fail to do this, it may interact with the paint and in the end the cast stone will have stains. Allow the surface to dry overnight after rinsing.

Step 3 – Protect Your Floor

Protect your floor by placing old newspapers or drop cloths around the fireplace. When you prime or paint the fireplace, the primer or paint can drip on the floor and can only be removed with solvent and scrubbing. The solvent may leave stains on the floor.

Step 4  Apply Primer

Use masonry primer on your cast stone fireplace. An oil based primer is more recommended. Apply one coat and make sure you cover all areas of the fireplace. Wait for the surface to dry. Apply a second coat or primer, which is needed because the cast stone is an absorbent surface. Allow the second coat of primer to dry overnight before you move on.

Step 5 – Paint the Fireplace

Paint the fireplace with an oil based paint and a bristle paintbrush. One coat of oil paint is typically sufficient. However, you can apply a second coat of paint as well. Allow 24 hours to dry before you seal.

Step 6 – Seal the Fireplace

Sealing the cast stone fireplace is a good idea, since the surface remains porous even after painting. Use a stone sealer and a paintbrush. Apply a coat of sealer, making sure to cover hard-to-reach places. The sealer can take up to eight hours to dry.