To help reduce buildup, manufacturers also make products that people can add to fires once they are burning to turn what could become creosote into ash, a powder that can just be brushed away. Rutland, for example, makes pre-measured three-ounce packets that can be tossed in once coals are forming (a three-pack of Creosote Remover Toss-In Tubes is $7.98 at Home Depot). Rutland also sells tubs of powder that people can scoop out and toss in to the fire (a two-pound tub, good for up to 32 fires, is $16.50). And there are squirt bottles filled with of creosote-preventing liquid, as well as logs and pellets (for pellet stoves) impregnated with these ingredients.
Although these products may have “creosote remover” in their name, they won’t solve your problem. They are designed to keep creosote from forming, not to remove it. You need an actual cleaner — one that’s safe to use on your hearth. Today, most wood-burning fireplaces are lined with fire bricks, which were invented in 1822. Usually tan, they are made of clay, as are regular bricks, but they are fired at a much higher temperature. The clay becomes partially vitrified, or almost glasslike, which allows it to withstand very high temperatures. Your fireplace is too old to be made with fire bricks. The hearth, or floor within the firebox, appears to be made of quarried stone with mortared joints.
For a cleaner, you could probably use a product such as Rutland’s brick and stone cleaner spray ($8.23 for a 16-ounce bottle). It is labeled for use on sealed brick and stone, but should never be used on firebricks or other unsealed bricks, said Will Hall, the company’s customer service manager. Unsealed brick can absorb the cleaner and the creosote it dissolves, he said. “It can be like a wet blob that can be absorbed into the brick.” If someone doesn’t know if brick is sealed — or, as in your case, if you’re dealing with an unknown type of stone — test in the least conspicuous place, then decide whether to use the cleaner on a larger area.
Or, before buying a specialty cleaner, you could start by seeing what you can accomplish with a grease-cutting detergent you already own or could use for other projects. Hand dishwashing detergent in hot water is an option, but a cleaner such as Simple Green all-purpose cleaner ($5.48 for a 32-ounce spray bottle) used at full strength might work better. Simple Green offers advice on its website about removing creosote. The company suggests using the foaming feature on its spray bottle to help the cleaner stay on the surface longer, but that’s probably more useful for cleaning a firebox’s walls than its floor.
If Simple Green works but you sense that a more powerful cleaner might do more, consider buying something marketed to professionals, such as Prosoco 2010 all surface cleaner ($55.95 a gallon on Amazon). Read the directions about how much to dilute the concentrate. Prosoco also makes an oil & grease stain remover ($49.75 a gallon) that lifts oily stains, such as drips from a car on a garage floor. Listed for use on stone, tile and concrete, this is a premixed poultice that you apply in a thick layer over the stain and then let dry. The poultice dissolves the oil, then lifts it to the surface as the product dries. A customer service representative for Prosoco said the poultice would be most effective if the creosote stains are oily and you use the poultice before you try cleaning with water. However, your hunch that the stains washed down with water during a rainstorm seems valid, given what the picture shows. That means the stains, at least at one time, were water-soluble, so if you’re lucky, they will still dissolve in wash water and can be cleaned away. Applying a poultice first would be safest but probably not critical. If you have a poultice product left from another project, do try it; it certainly will not hurt.
The Brick Industry Association, a trade group, generally recommends that you dampen both stained bricks and any bricks below that with plain water before applying a cleaning solution. This reduces the chance that grime softened by the cleaner will be absorbed into the pores of the brick. The advice makes sense when cleaning a stone hearth, too: Dampen the whole hearth, then put on protective gloves and apply the cleaning solution to the black area. Scrub with a wet, stiff-bristle nylon or other nonmetallic brush. Then quickly wipe or vacuum away the wash water and grime, using a masonry sponge, which can hold a lot of liquid, or a shop vacuum. Don’t use a regular household vacuum or even a vacuum designed for picking up fireplace ashes; the vacuum must be rated for picking up wet material. If the cleaner seems to be working but some of the stain remains, scrub again with fresh cleaning solution. When no more black comes off, rinse one or more times with clean water. Do not let the cleaning solution dry on the bricks or stone.
And what if you can’t erase the stain? Mask it. Consider covering the hearth with thin firebricks, which are sold in boxed sets for lining the floors of gas stoves, pizza ovens and backyard firepits. (A box of six Rutland firebricks 9 by 4.5 by 1.25 inches is $34.49 at Home Depot. If you need to cut the firebricks to fit, use a masonry blade in a miter saw (wear eye and ear protection), a wet saw for cutting tile or a hand saw such as the fire brick saw (lists for $26.67, with a spare blade, at Carbide Processors). Keep the firebricks in place by corralling them behind a strip of molding, attached where the hearth extension meets the flooring in the room. Check with your local building department about the fire-protected area you need for the gas stove you plan to install.
Or there’s paint. You might want high-temperature paint, rated to perform well up to 1200 degrees Fahrenheit, but unless it gets really hot — around 450 degrees — it won’t fully harden and might scratch more than regular paint would. The manufacturer of the gas stove you purchase might be able to tell you how hot the floor under the stove might get.
Have a problem in your home? Send questions to [email protected]. Put “How To” in the subject line, tell us where you live and try to include a photo.