Cleaning brick fireplace with muriatic acid

  • Active since 1995, Hearth.com is THE place on the internet for free information and advice about wood stoves, pellet stoves and other energy saving equipment.

    We strive to provide opinions, articles, discussions and history related to Hearth Products and in a more general sense, energy issues.

    We promote the EFFICIENT, RESPONSIBLE, CLEAN and SAFE use of all fuels, whether renewable or fossil.

gents

New Member
Nov 8, 2017
11
Upstate NY
My brick fireplace has some water damage and is generally dirty from 50 years of use. I grabbed some muriatic acid but there doesn't seem to be any good tutorial videos. Does anyone have any experience or found a tutorial that was helpful?
 
I have used muriatic acid quite a bit. It cleans very well, just be careful using it on stained brick as it will damage them. I always used it on thru colored brick so it didn't do anything but clean them

Craig
 
I have used muriatic acid quite a bit. It cleans very well, just be careful using it on stained brick as it will damage them. I always used it on thru colored brick so it didn't do anything but clean them

Craig

I just have standard red bricks , trying to remove the white water damage on the bottom left but figured I'd coat the entire surface. You wet the bricks first with water, apply the acid, and scrub with a brush? How runny will the acid be? Will it start to pool on the floor or if I use a conservative amount I can prevent that? Any tips would be appreciated.
 
The acid is diluted with water so it will be very runny, like water. I suggest using a small brush and dip it into the acid and "paint" it onto the bricks. I would do a small area first to see how it reacts. Make sure you have some clean water and a stiff brush to wash away the acid after you apply it and a household ammonium solution should be used as the last step to completely neutralize the acid.
 
I may just whitewash the old brick.
One of my SILs does some "faux painting." Here is the current iteration, and you can see a little bit of the former look she had on the brick, in the stove pic.
20191114_073336.jpg 087.JPG
 
Don’t apply muriatic acid without sufficient dilution. I’ve seen it completely dissolve and destroy a concrete floor, even at the somewhat tamed strength sold at Lowe’s Depot, when an idiot at work pulled that move.
 
Of course use gloves, a respirator, and goggles. Muriatic acid is very caustic. If you can clean the bricks with water and a coarse brush you'd be better off, but if elbow grease won't do the trick, using diluted muriatic acid will.
Use a solution of one part acid to 10-20 parts water (add the acid to the water and not vice versa) and test an inconspicuous area to confirm it won't discolor the bricks - certain bricks can't be cleaned with the acid. Soak the bricks well prior to cleaning and scrub the bricks with a brush starting from the bottom and working your way up. Work on small sections while the solution is foaming. Rinse it well. Cleaning bricks this way ages mortar joints dramatically, but since it's inside that shouldn't be an issue for you. The picture above with the white scale is your fireplace? That white scale is likely efflorescence which is caused by water entering the masonry from someplace. It'll return after you clean if the water isn't stopped.