Cleaning interior brickwork

[jack]

Hi all

 

We're starting to work our way through the outstanding to-do list.  A few of these tasks have been put off because they're awkward or we're not sure how to approach them for one reason or another.  I'm going to try and start posting questions about these so that I have one fewer excuse to not do them!

 

So this one relates to cleaning brickwork.  We have a couple of internal feature walls that are covered in stafford blue brick slips.  They mirror the part of the house outside that has the same.  We went for a light grey coloured mortar, but we learned from the outside clean-up that the colour doesn't survive acid-washing, so it's gone back to a more natural colour (which, as at happens, we prefer anyway).

 

We now want to clean the inside slips.  Here's what we have:

 

 

My question is how best to clean this off given that we're inside.  I can use an acid- based cleaner, of course, but does anyone have any tips on things like:

• whether or not to get something with detergents (rather than plain old brick acid) or thickening agents
• what sort of dilution, if any, we should be looking at
• what precautions we should take, other than the usual eye protection, decent gloves and old clothing
• to what extent should I be worried about fumes - what sort of mask should I consider, and should I be concerned about leaving things like furniture in the room?
• how much rinsing should I aim for?  We're working inside so obviously we can't just blast it with a hose!  Assuming I can get it properly clean, is it strictly necessary to rinse it?  HCl is a gas, so perhaps it'll just disperse on its own given time...

 

Depending on the answers to these questions, I was considering chipping away at lunchtime each day and properly cleaning a section at a time, working from the top.  That would give time for it to disperse each day before starting again the following day.  Any reason not to take this approach?

 

If you can think of anything else I should be considering, fire away!

 

Many thanks, as always

[joe90]

Jack, thanks for starting this thread, not that I need to clean up but it's prompted me to make sure my feature fireplace is covered up before plastering starts. Prevention is better than cure. 

[Jeremy Harris]

Hydrochloric acid.  Sold in 5 litre drums in Wickes, et al specially for the job as, unsurprisingly, brick and mortar cleaner!  Just use it carefully!  It's already diluted and don't add anything to it, in case it creates a reaction.  It should do the job on its own with a bit of patience and scrubbing.

 

It works because mortar (well, the cured cement in it) is soluble in most acids, and bricks, being fired clay, aren't.  It will dissolve the mortar if you're heavy handed with it, and you do need a stiff brush, long sleeved rubber gloves, eye protection and ideally something like a rubber or plastic apron to stop the stuff making holes in your clothes.

 

Easy to use, and should clean those bricks up better than most, because of their hard finish.  You have to pick the sort of firm bristle brush carefully, I managed to melt an old washing up brush because the acid attacked the plastic bristles.  It doesn't seem to attack the bristles on a stiff yard broom I have, the type that look "natural".

 

It's easiest to spray on with a small spray bottle, and do a small area at a time until you get a feel for it.  It can be quite hard work.

 

Don't be tempted to use power tools.  Years ago I tried a steel wire brush in a drill with the stuff, cleaning old render off a granite wall.  It throws small drops of acid everywhere (seems obvious now, but didn't to me when I was in my 20's.................).

Edited January 30, 2017 by JSHarris

[Mikey_1980]

I used these LTP Scourers for cleaning our external engineer brickwork, maybe less chance for acid flying anywhere with no bristles.

 

http://www.ebay.co.uk/itm/LTP-Emusifying-Scourer-Black-Pad-Coarse-Texture-/200805084725

 

[Jeremy Harris]

They look good, wish I'd known about them when I was cleaning up my own (rather rough) stonework.

[Mikey_1980]

They are very good, I have a long handled one on a pole to clean up the Patio Slabs, and the smaller hand held ones for the walls and corners etcs.  In my view its alot safer then a brush as it doesn flick everywhere, and they last well, and replacement pads aren't a huge amount.

[ToughButterCup]

And @jack, don't decant the HCl into a container with a leak in; even a pinhole-size leak eh?. 

[Jeremy Harris]

Also, don't get it anywhere near bleach!

 

When shock chlorinating our borehole (to kill off anything in there that had got in when I was faffing around cleaning it out etc) I had a problem with the Sodium Hypochlorite granules (the stuff that is dissolved in water to make liquid bleach) raising the pH of the water and so both limiting its solubility and decreasing the release of chlorine, needed to disinfect the well.  The standard fix for this is just to add an acid to lower the pH, get the solubility back up to what it should be, and all should be OK.  Now, it would have been safer, and far more sensible, to use something like acetic acid (distilled vinegar) or citric acid solution (distilled juice from lemons or other citrus fruits), but all I had to hand was a few litres of brick and mortar cleaner (dilute HCl). 

 

So, I measured the pH of the well water, estimated the volume, calculated the molar mass and poured in just enough HCl to get the pH back to around 7.  The result was a fairly large release of chlorine gas, to be expected, but on a somewhat larger scale than I'd anticipated.  Rather than stand at the well head, with the pump running and me holding a hose to wash the disinfectant down the side of the well liner, I had to just stuff the hose down the well and run for cover.  It took around ten minutes or so before the chlorine stopped coming out of the well head, and at one point it was actually visible as a pale green cloud, drifting across the garden..............

 

It did make sure the well was well disinfected though!

[SteamyTea]

We had a service technician that was trying to correct the PH on a spa bath.  He was mixing up chemicals and pouring them into the balance tank and then giving it a few minutes to circulate before manually checking the PH.

Silly sod forgot to turn the automatic chemical doser off.

The building had to be evacuated.

As Helen (Pippa Hayward) often said in the Brittas Empire "Remember what happened at Bedford".

[jack]

Thanks all.

 

16 hours ago, JSHarris said:

Hydrochloric acid.  Sold in 5 litre drums in Wickes, et al specially for the job as, unsurprisingly, brick and mortar cleaner!  

 

Yes, that's the sort of stuff I was trying to compare to ordinary muriatic acid. 

 

They seem to be a bit coy on the websites about HCl concentration, but I did see one product that was around 9% HCl, so about a quarter the concentration of muriatic.  I'm not sure what else is in it though.  My main concern about using something like this is the potential for residues given that I can't exactly hose down as I go, hence my reference to:

• whether or not to get something with detergents (rather than plain old brick acid) or thickening agents

Maybe these products are just watered down acid, in which case it's really cheeky charging more than the price of muriatic for the same size container at a quarter the concentration!  But if they do have detergents in them, then it might be better getting plain muriatic and watering it down.

 

16 hours ago, Mikey_1980 said:

I used these LTP Scourers for cleaning our external engineer brickwork, maybe less chance for acid flying anywhere with no bristles.

 

http://www.ebay.co.uk/itm/LTP-Emusifying-Scourer-Black-Pad-Coarse-Texture-/200805084725

 

They look perfect for the job, thanks for the tip!

 

15 hours ago, recoveringacademic said:

And @jack, don't decant the HCl into a container with a leak in; even a pinhole-size leak eh?. 

 

Oh no!  Photos? 

[Jeremy Harris]

I'd not use detergents, as you've no idea how they will react, just use the stuff sparingly, and rinse off with a damp sponge.  One thing to watch will be concrete polished floors, as the stuff probably attacks them too, as it dissolves cement pretty well.

 

 

[Ashburyselfbuild]

You could try this stuff, it is acid free. I used it to clean up an old mixer with great success. http://www.ebay.co.uk/itm/Cement-Concrete-Grout-Mortar-Dissolver-Remover-for-Tools-Buildings-Garden-650ml-/111785451126?hash=item1a06ee9e76:g:ROkAAOSwBLlVeGRr

 

 

[jack]

1 hour ago, JSHarris said:

I'd not use detergents, as you've no idea how they will react, just use the stuff sparingly, and rinse off with a damp sponge. 

 

I'm not talking about adding detergents as a separate product, I'm concerned that some of these "brick cleaner" type products (as distinct from plain acid) will include detergents in them.  But short of going to somewhere that sells this stuff and checking the ingredients list, I don't know whether they do.  Might just need to bite the bullet and drive to somewhere that sells it.

 

1 hour ago, JSHarris said:

One thing to watch will be concrete polished floors, as the stuff probably attacks them too, as it dissolves cement pretty well.

 

This is one of my major concerns, as there's polished concrete flooring along all the walls that need washing.  Shouldn't be too hard to protect.

 

1 hour ago, Ashburyselfbuild said:

You could try this stuff, it is acid free. I used it to clean up an old mixer with great success. http://www.ebay.co.uk/itm/Cement-Concrete-Grout-Mortar-Dissolver-Remover-for-Tools-Buildings-Garden-650ml-/111785451126?hash=item1a06ee9e76:g:ROkAAOSwBLlVeGRr

 

Interesting looking stuff, thanks.

[Jeremy Harris]

I'll have a look at the ingredients list later, as I have a 5 litre can of the Wickes stuff.  I'm near-100% sure that it's only diluted HCl, with nothing added, though, as I remember checking before using it to re-balance the pH in our well.

[jack]

Thanks Jeremy.  As it happens, I just had a look and notice that there's a Safety Data Sheet linked from the Wickes site.  Apparently it's 5-10% HCl (so perhaps around the 9% HCl I saw somewhere on a similar product), so as you say, dilute acid only.

[Jeremy Harris]

Beat me to it!  I'm just back and was going to say the same.

 

Taping some polythene sheet down well should protect the polished concrete; polythene is not affected by HCl.  I think those scouring pad things that Mike linked to should be ideal, then just a bucket of water and a sponge to rinse the brickwork off.  If you just let the dilute HCl evaporate off it won't leave any toxic residue behind, but rinsing with a damp sponge will just remove the dissolved mortar.  With a bit of luck, using is sparingly like this you shouldn't get the discolouration you saw outside, as I suspect that was most probably the HCl dissolving out the white pigment, which may well have been something like hydrated lime, which is highly soluble in HCl.

 

If you have the patience, it might be and idea to just try and clean each slip one by one, trying to keep the HCl off the mortar joints.  I have a feeling that this white mortar is probably pretty soluble in it, and so may just almost wipe off.

Edited January 31, 2017 by JSHarris
typo - missed out an important "not"!

[jack]

Thanks Jeremy, the polythene sheet was already in the plans.  Thankfully we still have a gap between bottom of the wall and the concrete floor, so I should be able to work it so that any wayward drips get directed away from the junction onto the sheet.  

 

And yes, based on what we saw outside the colouring comes straight off (glad we paid extra for coloured mortar!)

 

I actually prefer the raw mortar - looks more natural - so am going to experiment somewhere out of the way to see what it looks like if I clean the mortar as well.  I do plan to do this in sections so I can chip away at it a bit every day rather than tackling the whole job at once.