Correct dilution of muriatic acid

Stan in Oly, WA

Well-known Member
The chimney on my house is made of a light shade of Roman brick. It is badly discolored by creosote and soot. Last year while I was working on something else on the roof, I spent a few minutes experimenting to see whether I could clean it with common household cleaners. Nothing worked. I use muriatic acid diluted with water to a one sixth concentration to clean the low brick walls around the flowerbeds when they get too stained by black algae, but I don't know if that would be right for the soot stains on the chimney. Does anyone know the proper dilution of muriatic acid for this job? I'd prefer to get it done in one try. Thanks.

Stan
 
They commonly use a diluted muriatic acid solution to wash mortar off of brick after laying up a wall. I don't believe you will remove the creosote stains, might lesson them some. A bricklayer may have the dilution rate. gobble
 
I use that stuff fairly often to clean stubborn grout stains and I periodically clean the toilet bowl of calcium deposits with it.
I recently cleaned a badly stained stucco retaining wall with it.
I dont have an exact mix ratio for you though. On the retaining wall I hosed it down to get it wet then poured about 1 qt of muratic acid in 3 gals of water.
I sprayed the mix on with a pump type garden sprayer.
It was a hot day and the mix wanted to dry so I misted it with the hose to keep it wet and work longer.
Then I powerwashed it with a pressure washer.
Came out looking real nice.
I would try that ratio on your chimney and it should help it look better.
 
Using acid to remove creosote and soot is the wrong chemistry. Acid removes minerals like hard water deposits and rust stains. Creosote and soot are not mineral deposits they are more like tar. Acid won't do a thing to remove them. You need to use a caustic cleaner like oven cleaner.
 
I agree,,,acid will only hurt the cement joints at this stage.Maybe test simple green on a spot,,see what it does,,it wont damage the mortar like acid could
 
A solution of cloudy Ammonia and detergent will shift Creosote. It is a tar as such and needs a powerful surfactant to move it .
Acid is wellnigh useless but for future reference 4 to 1 water to acid will shift the most stubborn of old mortar stains on brick and stonework. And of course always add the acid to the water not the other way around .
 
dpendzic; I Googled Rutland creosote remover. The description said that it is primarily for dealing with creosote inside a chimney, stove, or fireplace. I thought that it might also be suitable for removing soot and creosote on the outside surface of my chimney above the roof, but the instructions say that it is heat activated at 265 degrees F. If the exterior surface of my masonry chimney ever got that hot, cleaning it would be the least of my worries. Thanks for the information, though. I could still use the product for its intended purpose.

Stan
 
Thank you everybody for the information. It sounds like a caustic cleaner is the way I have to go. I hope it cleans the brick surface of the black stains from algae, lichen, or mold, too. Otherwise I'm going to be up there cleaning it twice---once for each different kind of stain. I consider it a fairly easy job. The hardest part will be convincing my wife that I'm far enough along in the recovery process from rotator cuff surgery to get on the roof to do it. I'd gladly wait until later in the year to do it---there will be months of good weather ahead. But we're getting a new roof next week and I'd like to stay off it as much as possible.

Stan
 
(quoted from post at 06:30:27 06/17/18) I agree,,,acid will only hurt the cement joints at this stage.Maybe test simple green on a spot,,see what it does,,it wont damage the mortar like acid could

Larry, house hold simple geen is intended to be gentle to your skin so it is not likely to be effective on something as tough as creosote.
 
there are two forms of it--powder that is heat activated and you throw it in the fire---and a liquid spray bottle that i use om ambient surfaces
 

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