Recently I asked a question about how best to brighten brick on
an old fireplace and now have a good database on that subject.
But now I would like to know how to brighten dingy, smoke-discolored
mortar, which may require a different approach (??) I have tried the
standard, non-reactive cleaners and they don't work. I have also
heard that muriatic or phosphoric acid solutions may work, but I
wanted to consult the experts before trying anything.
Could someone set me straight on this? (Whatever is suggested,
I am prepared to take all necessary safety precautions, but I want
to avoid "wimpy!")
Thank you for your help.
Muriatic acid is for brick cleaning....I think it breaks down the
mortar or something.
I would try some muriatic acid and a stiff brush but I wonder how far
that smoke has embedded itself in the concrete....it may have over the
years "stained" the mortar making it near impossible to remove without
getting off a thin layer of the mortar itself.
Have you tried a product such as greased lightning or simple
green...maybe try some vinegar on the mortar...you probably have some
at home so you could make a quick test.
Im just offering suggestions....no actual experience...
I have removed heavy cigarette residue from bar equipment
before...20-30 years worth but it was from wood and metal
surfaces....used greased lightning and it worked well
Ive used muriatic acid inside and out, its dangerous enough outside
because it fumes and burns your lungs. If you want to do it get a fume
respirator, realy a paint respirator, several fans to remove air fast
outside, use a nylon broom-brush on a pole to apply it and leave fast,
and let it work for 15 minutes or so, then scrub with a stiff nylon
brush on a pole. Now you need to rinse it clean with gallons of water,
and of course you have protected the floor and absorbed everything with
old towels you put in a garbage can, take outside and dilute the acid
Thank you all. Any of the conventional detergents will
NOT work. I have a product in a spray can designed to
clean brick and, while it brightens the brick somewhat
it won't touch the mortar.
Whatever will get the mortar clean will have to react
with it, not just sit on the surface. I am expecting I may lose
a tiny bit of the surface in the process, but I assume that
can be controlled by the dilution ratio.
Nobody ever mentions phosphoric acid which it seems
might be less caustic than muriatic. Yet I have seen a couple
of products on the net which SEEM to address the grout
problem. I keep hoping some comments about phosphoric
will turn up here.
Anyway, thanks again and I am prepared to try muriatic
if I don't come up with other suggestions.
P.S. Can't I stop the acid with some kind of base to
neutralize it rather than just plain water? Suggestions?
I think soot is mostly carbon. According to the CRC Handbook the only thing
in which carbon is soluable is liquid iron and then at less than 1% (that's
how you turn iron into steel).
I'll bet you have to either mechanically remove it (wire brush, etc.) or
cover it with something else (paint or more mortar).
++++++++++WARNING DO NOT ADD AMONIA TO MURATIC ACID++++++++++++
the color of your joints will be the least of your worries...Regular
hosehold white or cider vinegar will neturalize muratic acid..But
muratic acid it not a stain remover persay it will remove cement based
stains and once you get the soot and other crap off of the joints you
can paint on a dilution of it with a small paint brush and it will
brighten it a bit. I have had good luck with (powered) T.S.P the liquid
That is what I was planning to do, with a toothbrush. True
TSP (trisodium phosphate) is almost impossible to find as it
has been replaced with a "substitute" (sodium metasilicate.)
I think that's what the liquid contains and that is why it
As to your warning, I quote:
Scrub off any remaining residue with a stiff brush while rinsing
thoroughly with water. There are long handled masonry brushes ideal
for this job. To neutralize any remaining acid, you can spray a
neutralizing rinse of one (1) cup household ammonia to one (1) gallon
Ammonia is a base and bases neutralize acids, as I understand it.
You have a few idiots here recomending BS, Vinegar is an acid, not a
neutraliser. Amonia is just as bad for your lungs as acid, try to use
the least toxic way to harm yourself. Muriatic works but contact
Detrict Chemicals out of Minnesota or Wisconsin, all they do is make
stone and brick acid cleaners. Detrich usualy only sells 5 gallon lots,
but try them. Sure you can neutralise it but it still must be diluted
with a water wash, I have done it with finished oak floors, no harm
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