If you're reading this you have probably already searched the internet for ways to cleaning all that unsightly and smelly creosote, tar and soot that builds up from wood burning, off your masonry firebox firebrick. If you haven’t searched yet – save your time: most of the information you’ll find there is related to costly cleaning products for sale, services to hire and an array of methods and concoction to use that are: at best - functionally questionable, at worst – dangerous (sandblasting), damaging (use a steel-wire brush) or just stupid (painting-never, never do this). Here’s a solution that simple, safe, inexpensive and effective.
But…… before we go any further lets set an expectation of what I mean by Clean Firebrick. Checkout the picture of my fireplace which, I believe, represents what results you can expect using this method. Clearly I realize the firebrick is not spotless or new in condition but considering the fireplace is 29 years old, is used over 4 months a year on average of 8-10 hours a day......I think a fair assessment of its condition is clean. So if you're still interested....read on.
(Note - It is not the intent of this guide to detail the standard, common-sense safety consideration, like reading product labels, warning protect glasses, gloves, etc. you should use when cleaning or using cleaning products. Naturally you should follow all standard safety practices when performing the following instructions.
It really couldn't be much simpler:
– Buy a box (not liquid concentrate) of powdered TSP (Trisodium Phosphate). It comes in 1lb. and 3lb. sizes at HD, Lowes, Ace Hardware, etc. (3lb. box cost about $11 and will last for years).
– Mix two ounces of TSP into a 32oz. spray bottle of hot tap water (it only dissolves well in hot water). Shake it vigorously for 30 seconds or so until the powder dissolves.
– While burning wood, with the fireplace nice and hot, spray it liberally (the entire 32oz. bottle over an evening application) onto the firebrick.
Couldn't be easier - The spray hitting the hot brick will dissolve the creosote, tar and soot off the brick and inhibit future sticky buildup. Do this about once ever two weeks or so, depending on frequency of burning, during the burning season and then at the end of the season for each of the last few fires. After you remove your fireplace heater/grate for storage, clean out the ash, mix a solution of 4 ounces of TSP to a half-gallon of hot tap water and lightly scrub the firebrick with a soft bristle scrub brush. Then just soak up the dirty water with a rag into a pail and you're done. Generally pretty easy work!
Note: never use a hard bristle brush for scrubbing the firebrick. The best brush I found for this is a plastic brush with plastic bristles - generally available at any Dollar Store for..... $1).
Clearly the results you get will depend largely on the condition of your firebrick before you start using this cleaning solution. New firebrick should come up looking just slightly used, firebrick with years of creosote/tar buildup will require more applications of cleaner during the burning season and/or additional, stronger cleaner mixtures/scrubbing to remove the buildup. Regardless of its starting condition, over time, with very little effort, your firebrick should become tar/soot free.
Hope this is helpful - FireplaceFurnaces
PS: Sprinkling an ounce of TSP regularly onto a bed of burning embers during the burning season will help reduce the creosote/tar buildup in your fireplace flue. Basically it’s the same stuff they use in CSL log and the like and like those logs it is not a substitute for having your flue cleaned and inspected regularly.