Remove old cement from bricks using hydrochloric acid (muriatic acid)

10 Jun 2014
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United Kingdom
I have exposed my fireplace opening and have been carefully cleaning up the bricks with a cold chisel and wire brushes. I want it to look nice as it will be left exposed.

Unfortunately there is still residue of cement, some of it in large chunks. I can't remove it without breaking the bricks.

Next plan is to apply hydrochloric acid, or muriatic acid as the Americans call it. I know this is killer stuff so I will be very careful. Has anyone done it before, or got any other tips on how to get these bricks clean?

Some pics of it as it is now:

2015-11-24 21.46.05.jpg 2015-11-24 21.46.28.jpg 2015-11-24 21.46.39.jpg

Thanks for any advice
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Brick acid is good at removing residue and smears but not at removing lumps.

I had good results previously cleaning exposed brick on a chimney brest with a flap wheel. I then painted the bricks with a thin coat of polyurethane varnish to keep the dust down.
A flap wheel wont touch that lot but make a nice dust all over the house. You need to chip off the heavy stuff. I find a scutching chisel best, then get some water and a scrubbing brush and see how it looks.
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but not at removing lumps

It will eat the cement and soften the lumps, which then will scrape off.

Use it neat on lumps first, and then diluted on the rest of it. Try and keep it mainly on the brick faces, and out of the joints. Remember to wash it all off afterwards though.

A hand wire brush is enough
Soak the brick before you put the cleaner on, else it will soak in and not touch the surface. It dissolves the cement /lime between the sand particles, so after the fizzing has stopped use a stiff brush to knock the sand off. repeat as required.

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