Brick Fireplace Cleaning
Your brick fireplace gets dirty with use. Smoke and soot sink down into it and get absorbed. Ashes land on the brick and get ground in. If you roast marshmallows or pop popcorn, food oils can also make their way down into the pores of the brick. To prevent these dirtying particles from becoming a permanent design feature, your brick fireplace will need regular cleaning. Here's how to go about it. (Note: Very old brick, say 50 years old or more, can be damaged by vigorous cleaning. Test an unobtrusive corner to see and adjust your cleaning practices if needed.)
Get the brick sealed. The easiest way to keep your fireplace clean is to minimize how dirty it can get. A good sealer won't completely prevent the brick from absorbing dirt, but it can help. And the dirt that does get absorbed can be kept near the surface where it's easier to scrub it out.
You're going to need to scrub pretty hard, and the water you use may be quite hot. Protect your hands.
Lay down some newspaper on the hearth and pull out chunks of charred log. Sweep up the ash. There's no point in trying to clean the brick if your scrubbing brush is just stirring up ash and dirt in the process. These particles will float in the air and gently land on the clean surface after you're done.
Mix an ounce of soap with an ounce of table salt and just enough water to make a thin paste. Use a cloth to spread this mixture over the surface of the brick with just enough force to get it into all the tiny pores, nooks, and crannies. Wait at least 10 minutes to allow the mixture to dry. Remove the mixture with a stiff scrub brush. This may be all the cleaning your brick needs. If so, proceed to the last step to rinse the brick.
If the dirt is particularly greasy, you may need to follow this additional step. Mix detergent, pumice, and a little ammonia with hot water into a paste. Spread the mixture with a brush onto the brick surface and let it dry. Use a wet scrub brush to remove it.
Your brick may still need more cleaning. A stronger treatment can be had with the use of trisodium phosphate or another commercial fireplace cleaning product. Dissolve 1/2 cup to a cup of trisodium phosphate into a gallon of hot water. Scrub this thoroughly into the brick surface and rinse with warm water. Repeat as necessary.
Soap is great at attracting dirt. That's how it works. And that means you want to make sure there isn't any soap left behind. Get a bucket of warm water and scrub that into the brick when you're done with all the methods above. You may want to use a different scrub brush or at least thoroughly rinse the one you've been using. This isn't the time to be putting more detergent in. Use a towel to dry up the brick so that the soap doesn't just seep back in as the water evaporates.