In Britain, for centuries, the job of cleaning fireplaces and chimneys was left for the soot covered good luck charm of the time, the chimney sweep. It was considered good luck to shake a chimney sweeps hand, even though their poor life span was typically cut short by the amount of soot that they ingested into their lungs…
Today you can still hire a chimney sweeping company to clean your chimney and fireplace, but if you typically only use your fireplace sparingly, like for parties or the occasional late winter marshmallow roast, here are a few suggestions for cleaning your fireplace yourself.
First, remove the hearth or insert and sweep out as much of the left over ash as you can and then go over the surface with a hard bristle brush and very hot water. This will reveal how dirty the fireplace really is and give you a good idea of how strong your cleaning solution needs to be. Often a good sweeping with the right kind of broom is good enough. Have a stone or brick fireplace sealed with a surface sealant that repels soot and grease when you move into a new home or after you've cleaned the fireplace thoroughly.
When cleaning fireplaces, always wear rubber gloves--the chemicals can be caustic to the hands and absorb into the skin, causing rashes and possible allergic reactions. It is also a good idea to wear a dust mask (too bad chimney sweeps didn't know to do this.)
Make up a cream like cleaning substance using salt and mild soap and water. Rub onto the soot covered bricks and let stand for about ten minutes. Use a clean, short handled bristle brush to scour the cream off. The salt acts as a pumice stone.
You can also use ground pumice, ammonia, and a little hot water as a cleaning solution, but make sure that there is proper ventilation if choosing to clean this way. The best bet is to make sure that the flue and front door are open. This is a good solution if there is a large grease build up on the brick or stones.
There is a chemical called TSP available at hardware stores and home improvement centers. This solution is great for cleaning fireplaces and anywhere else in the home where the grime is particularly bad.
Sweep the hearth of the fireplace well after each use, and using a hard bristle broom is best. If you keep up on it, the soot will be minimized and cleaning fireplaces will be easy. This only has to be done once a year and can be a good addition to spring cleaning, but better yet, clean your fireplace as soon as you're relatively sure that you won't be using it for awhile. Make sure that you rinse the surfaces that you clean well with lots of warm water, as residual chemicals, when lit on fire for the first wood burning session of the winter, can cause an explosion or at the very least cause quite the stench!