The hearth refers to the part of the fireplace that rests on the floor and sits directly in front of the firebox. Hearths consist of a fire-resistant material such as stone, tile or brick and can be exactly flush with the floor of the room or slightly raised. If your fireplace could use a fresh facelift, consider splashing the hearth with a coat of paint. This will give you an idea of what the rest of the fireplace will look like painted.
Pour 2 gallons of warm water into a large bucket. Add 1/2 cup trisodium phosphate.
Dunk a heavy-duty sponge into the mixture and wring it out. Rub the sponge against the hearth. This will remove soot and other caked-on material. Rinse thoroughly with clean water and a clean sponge. Allow to dry.
Apply a spackle to cracks or dents in the hearth with a special brick and mortar repair substance. Most of these types of spackle come in a tube with a tapered end like a syringe, which makes applying it simple. Allow the spackle to dry.
Tape off the area on the floor around the hearth with painter's tape. Apply a universal acrylic primer to the hearth with a paintbrush or roller. Allow it to dry and apply another coat. Let this final coat dry.
Apply a coat of water-based acrylic paint in your desired colour. Make smooth strokes from the top of the hearth down to the bottom with your paintbrush. Allow the first coat to dry before applying a second coat, making strokes of paint in the same uniform manner. Remove the painter's tape before this coat has a chance to dry.
Wear rubber gloves when working with trisodium phosphate.