Clean soot out the bricks of old fireplace

We had a backboiler and gas-front removed from our living room fireplace recently. We've had the flu liner pulled from above and the chimney fitted with a vent cap, and the plan is to install some hardiboard with a vent just out of sight at the bottom to keep the chimney ventilated. House was built 1919.

Yesterday we opened the fireplace out to the builder's opening and swept out all the crud. Noting that the fireplace would have been used with coal for 50+ years I'm not surprised that the old bricks are stained black, but I'd like to try and clean it up instead of boarding it out or plastering.

As the room is completely stripped and has a concrete slab floor, I can make some mess in the process. I was wondering about either brushing on a load of brick acid, letting it sit and then washing it down. I could even try using a pressure washer and having Mrs D try and keep up with the wet vac.

Anyone had success or failure at getting this done? Any wisdom to share?

IMHO there is no practical way of getting the black off - I tried on mine initially, and then decided to leave it as it was as it showed the history of the old range that used to be there. The other issue is the bricks will be absolutely loaded with salts - the products of combustion react with lime to produce acids and salts. Don't use a pressure washer - I tried that too and a) it didn't work and b) took a very long time to dry and c) activated salts and grew lots of white fur. I also tried a little brick acid, wire brush etc etc.

In the end, I just pointed it up. With the gas "log burner" in the hole it looks good.

Thanks, looks very familiar!
Did you put anything on the bricks to seal in the staining?

Did you put anything on the bricks to seal in the staining?

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No. They are still prone to a very little efflorescence just from natural humidity in the room. (because salts are hygroscopic) I figured it's easier just to brush off than risk bubbling up underneath any sealant