Acid cleaning bricks

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David321

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#317751 12-Nov-2024 11:00

Hi all,

A while ago I posted about hard water stains on dark brick work, no replies unfortunately but I acknowledge it's not a very common problem.

I thought I would share an update, hopefully this might spark some discussion/sharing of knowledge around this.

I knew from reading what I could online (there is not much info) and after talking to many different people including the brick manufacturer and specialist concrete treatment providers, that hydrochloric acid is an option but should be used as a last resort due to the risks involved, mainly cosmetic damage to the bricks and personal safety.

After trying all sorts of things such as the new environmentally friendly alternatives to acid (used for etching concrete to make exposed aggregate) and having no luck at all, I went and got my hands on some hydrochloric acid and all the proper safety gear.

After the first application and a very touch scrub (drill brush attachment) followed by a good rinse there has been slight improvement (photos to come). Knowing that the acid is the strongest product I can use for this staining and how much work is involved it's crazy to think how long this is going to take and how much effort will be involved as it is going to take repeat applications and I am cautious about using a stronger mix of acid as I am using the maximum strength advised (1 part acid 10 parts water) , but I am determined to get it done and get the bricks looking good again.

My two main questions are, is anyone familiar with either these stains on bricks and/or acid cleaning bricks, perhaps you could through some tips my way?

Also, I really want to prevent this happening again so am looking at sealing the bricks once clean and also perhaps adding some sort of filter to the outside taps to block/reduce the minerals that cause this staining (I think its calcium and magnesium but not sure).

_David_

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Smpl Mnmlst
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#3307983 12-Nov-2024 11:26

Not wanting to second-guess you but is it caused by hard water getting onto the bricks (i.e external) - or is it efflorescence coming from salts or minerals in the bricks (or the mortar) coming to the surface? What did the brick manufacturer say? I just found this which seems pretty authoritative and useful.

IANA expert but looking at the distribution of the deposits in your photos (particularly the second one), I would be surprised if it has come from tap water getting on the bricks. By adding some sort of filter to outside taps you may be barking up the wrong tree.

Edit: Also just found this for a NZ context. It mentions water coming up from the ground and into the bricks via capillary action - and that may explain the stains on only the lower part of the wall in your second photo. You may need to check the drainage around the footings of your house in the affected areas.

See these Google results.

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qwertee

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#3307986 12-Nov-2024 11:40

I had efflorescence on my patio tiles, but chose to leave it .

If you are sealing just do it on an a few bricks on the side of the house that is away from general view.

I used a water based sealer . Dont make the mistake I did when I did the whole lot in go.
It was hideous , specially when I went over the grout lines with a brush.

See photo. But it has now evened out over 2 years.

eracode

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#3307989 12-Nov-2024 11:49

qwertee:

I had efflorescence on my patio tiles, but chose to leave it .

If you are sealing just do it on an a few bricks on the side of the house that is away from general view.

I used a water based sealer . Dont make the mistake I did when I did the whole lot in go.
It was hideous , specially when I went over the grout lines with a brush.

I'm a bit confused. You say you left it - but then say you sealed them. Do you mean you put the sealer on without trying to remove the efflorescence?

Sometimes I just sit and think. Other times I just sit.

David321

485 posts

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#3307998 12-Nov-2024 12:09

I should have mentioned in the post, I spent a while thinking it was efflorescence but after doing all of the standard test to confirm I slowly worked out it was hard water staining.

I cant remember all of the tests off by heart to determine it was not efflorescence but one of the big factors was this staining is actually on the black aluminum windows also in the same areas, this was pointed out to me by a bricklayer who agreed it must be hard water stains.

Looking at the pattern of the staining and how the property is layed out it becomes evident it would be a typical sprinkler pattern.

_David_

eracode

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#3308002 12-Nov-2024 12:18

David321:

I should have mentioned in the post, I spent a while thinking it was efflorescence but after doing all of the standard test to confirm I slowly worked out it was hard water staining.

I cant remember all of the tests off by heart to determine it was not efflorescence but one of the big factors was this staining is actually on the black aluminum windows also in the same areas, this was pointed out to me by a bricklayer who agreed it must be hard water stains.

Looking at the pattern of the staining and how the property is layed out it becomes evident it would be a typical sprinkler pattern.

Ah yes - that would have helped a lot.

Sometimes I just sit and think. Other times I just sit.

qwertee

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#3308004 12-Nov-2024 12:25

eracode:

qwertee:

I had efflorescence on my patio tiles, but chose to leave it .

If you are sealing just do it on an a few bricks on the side of the house that is away from general view.

I used a water based sealer . Dont make the mistake I did when I did the whole lot in go.
It was hideous , specially when I went over the grout lines with a brush.

I'm a bit confused. You say you left it - but then say you sealed them. Do you mean you put the sealer on without trying to remove the efflorescence?

Sorry for the confusion. I didnt use any strong chemicals to remove it. I only cleaned the surface deposits and sealed them.

Rikkitic

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#3308073 12-Nov-2024 13:01

I don't know anything about this and this question probably proves that: Can't bricks be painted?

Plesse igmore amd axxept applogies in adbance fir anu typos

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neb

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#3308077 12-Nov-2024 13:11

Rikkitic: I don't know anything about this and this question probably proves that: Can't bricks be painted?

Anything can be painted, it's more a question of should bricks be painted. The general advice is no since it'll trap moisture inside, and the paint will flake/peel after a time requiring repainting, a lot more than (say) fibrolite cladding or similar would.

neb

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#3308081 12-Nov-2024 13:15

If it's from hard water what about using one of the million products for dealing with that, that are less vicious than hydrochloric acid? One you can try at very low cost is to heat white vinegar, apply it with a spray bottle and leave it for a few hours (reapplying if necessary) to dissolve the stain, then wash off. You don't need a particularly strong acid to deal with what's presumably mostly calcium deposits.

David321

485 posts

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#3308113 12-Nov-2024 14:03

neb:

If it's from hard water what about using one of the million products for dealing with that, that are less vicious than hydrochloric acid? One you can try at very low cost is to heat white vinegar, apply it with a spray bottle and leave it for a few hours (reapplying if necessary) to dissolve the stain, then wash off. You don't need a particularly strong acid to deal with what's presumably mostly calcium deposits.

Been there done that, no effect whatsoever. Boiling waiter, wire brush, stiff nylon brush, water blaster, straight white vinegar, green acid replacement - you name it i've tried it.

The fact that even hydrochloric acid is going to take multiple applications to remove it completely speaks volumes to how stubborn this stuff is.

_David_

eracode

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#3308133 12-Nov-2024 15:08

Do you know for sure that you have hard water?

Sometimes I just sit and think. Other times I just sit.

neb

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#3308145 12-Nov-2024 15:32

David321: Been there done that, no effect whatsoever. Boiling waiter, wire brush, stiff nylon brush, water blaster, straight white vinegar, green acid replacement - you name it i've tried it.

Possibly a redundant question but how long did you leave the acids on there? They should dissolve the material and just rinse off, not need mechanical assistance, you just need to leave them for quite awhile (and reapply if they're drying out), typically several hours.

Edited to add: Not questioning your cleaning or anything, just making sure all the bases are covered, the stuff seems suspiciously tenacious for hard water stains.

Another thing you could try is phosphoric acid, which you can get relatively cheaply on TM. It's also a fantastic rust remover, it's the active ingredient in various much-more-expensive scale/rust removers.

David321

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#3308201 12-Nov-2024 17:12

Do I have hard water? It appears so from the staining and the fact soap doesn't bubble up in our water is also a tell tale sign apprently.

As for length of time leaving the vinegar, I didn't time it but it was quite a while. As for the acids I can't leave them to long as its important they don't dry and most instructions say no more than 10 mins.

_David_

mattwnz

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#3308270 12-Nov-2024 21:02

In the UK where bricks are common, they usually have a damp proof course between the brick and the foundations. Do you have a damp proof course. Is the ground often boggy in these areas? You do get this issue sometimes with solid concrete block walls.

jonherries

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#3308283 12-Nov-2024 21:15

I have had really good success with hard water stains on glass with Barkeepers Friend. Comes in a squirty bottle and I think it is Oxalic Acid.

Used it on bathroom glass that I then treated with Rain-X - and it has now lasted with regular weekly cleaning ~12 months with no more water staining.

Jon

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