Muriatic acid, removing excess mortar, brick steps repair

[TomR]

I am in just finishing repairing and repointing brick steps like the ones shown in the following YouTube video:

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I made a bit of a mess while doing it, so I am going to want to remove the excess mortar stains and film that I left on the bricks. My plan is to use muriatic acid, and I may buy this stuff -- Kleen Strip muriatic acid -- from Home Depot:

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However, I would like to get some more specific instructions or find a good YouTube video that explains how to do this mortar clean-up.

I am not sure how much to dilute the muriatic acid, and I don't know whether to spray it on, or just brush it on, or whatever. Unfortunately, none of the YouTube videos that I could find actually showed how to do this.

My plan right now it to wet down the steps with water, then dilute the Kleen Strip muriatic acid to about 1 part acid to 4 parts water, brush it on, let it sit for a few minutes, then rinse it off thoroughly with a hose.

Any other help, ideas, or suggestions would be appreciated.

[nestork]

Tom:

When I took a short bricklaying course about 20 years ago, a trick bricklayers used was to nail a piece of level loop nylon carpeting around a short piece of 2X4 lumber, and use that as a brush to scrub the soft mortar off the brick face as they laid the bricks. Because the mortar joints are recessed from the brick faces, the carpet will scrub the brick mortar off the brick faces without scrubbing it out of the mortar joints.

I would try using a paint scraper to remove as much of the dried brick mortar from the brick faces first. Watch to ensure the paint scraper doesn't leave marks on the bricks. If so, switch to a paint scraper with a tungsten carbide blade. If push comes to shove, full strength muriatic acid will remove any marks the metal leaves on the bricks.

The instructions you linked to say for brightening masonary and brick work, mix 1/2 pint of acid per gallon of water, which is far less than the 4:1 you were intending to use. If it were me, I wouldn't start with any more than a pint of acid per gallon of water, or about a 8:1 dilution ratio. You can always add more acid if it's not strong enough and doesn't seem to be doing anything. Try that on a small area and scrub with a toilet bowl cleaning brush to see the results.

The acid brushes they sell in brick supply places look kinda like a big toilet bowl cleaning brush with yellow polypropylene bristles about 3 inches long on one side only. I'm thinking you can just use a toilet bowl cleaning brush for a small project.

Then spray the whole thing down with your garden hose or a hand pump garden sprayer and allow to dry. Maybe wipe up any water puddling with a sponge.

[micky]

You're talking about stains and film I gather. ;=)

Not actual excess mortar, I only know about getting actual mortar off.

I'm not sure if everyone would have called it excess mortar and the house looked pretty good until I looked closely, and then I was bothered one day by many places where the mortar overflowed the space between the bricks. It had the normal depression, channel, groove, but there was, as I say, stuff ovelapping the brick below the mortar layer, and maybe even the brick above.

I used a hammer and cold chisel. And eventually jus a hammer, after I learned how hard to hit it so the excess mortar broke off but the nothing else was bothered. I spent a couple hours at this, and only did from 1 or 2 feet high to 5 or 6 feet high, and only 5 or 10 feet horizontally. But only the first floor is brick. I didn't get much of the side or any of the back of the house, but I got the part I see every time I come home, and I haven't noticed the extra mortar since.

[TomR]

Thanks. I should have explained it a little better. There aren't any excess pieces of mortar left on the bricks because I brushed the excess off before the mortar dried. But, there is a lot of white mortar-stained areas on the brick -- a translucent thin film of what was mortar and water. I am assuming that the muriatic acid will react with that and dissolve it and then can be rinsed off with water.

Yes, what they describe is about a 16:1 dilution ratio to "brighten" masonry and brick work. But, even though on the lable there is a mention of "removing excess mortar", there are no instructions on whattype of concentration to use for that. Maybe I'll try starting with about an 8:1 ratio first as you suggested.

The label is also confusing (to me) about what the concentration is of the muriatic acid that is in the bottle. It says something about 20%, which I assume means by volume, and then says it's 31% by weight.

I don't know what strength regular muriatic acid is, or what strength brick masons use for this type of clean-up work after repointing brick with new mortar that isn't fully cured.

I do have a masonry brush like this one that I used to brush off the excess mortar before it dried:

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Maybe I'll try using that to brush on the muriatic acid and then rinse it off with a hose.

[dadiOH]

Those strengths are the norm. Just use one part of that to "X" parts of water. And ALWAYS add the acid to the water, NEVER vice versa.

Start with a very weak mix...if that doesn't work for you, increase the strength until it does. What you want to remove probably won't require more than a very weak mix.

[TomR]

Thanks. I'll try that -- probably in the next day or two. I'll post how it works out.

I may try posting a 'before I started the repair" photo, an "after my sloppy repair job and mortar work", and an "after the muriatic acid clean-up" photo.

I did such a crappy job with the mortar that I am a little reluctant to post how it looks, but I may post it anyway.

One side note: When trying to do the repointing, I tried buying and using mortar/grout bag like this one to apply the mortar in between the bricks:

I couldn't get it to work correctly. The problem that I had was that the only way that I could get the mortar to come out of the bag reasonably well was if I made the mortar too liquid and soupy. Anything thicker than that was almost impossible for me to get to come out of the bag even while squeezing hard. It would just get clogged in the opening. I tried cutting the tip to make a larger opening but that didn't help much. And, I did mix the mortar well so there were no clumps. I finally just gave up and I decided to apply the mortar by hand -- hence the sloppy mess that I now have to try to clean up.

[RobertMacy]

Couldn't get that URL to work, ended up on Halloween Decorations, so gave up.

However, I use the type S mortar mix from HD. Very difficult to insert the mortar into cracks. So I made my own method, used a plastic funnel cut down, and simply squeegee the mortar to kind of where I want it to go. Probably lose half of what goes up. But a stiff brush removes the damp, not set yet, mortar.

PS: my mistake was not knowing you're supposed to 'slake' the mortar [if that's the correct term] let it sit, 10 minutes, mix again and THEN use. Once I learned that [directions as shown on grout mix!] really made a difference! The type S mortar changed consistency and started acting like mortar instead of wet sand.

[TomR]

Sorry the link didn't work. If you want, you could go to HomeDepot.com and do a search for, Blu-Tip 12 in. x 24 in. Grout Bag , which is what the item is called.

I didn't use the Type S mortar ( Quikrete 80 lb. Type S Mason Mix ). I used the regular mortar mix ( Quikrete 60 lb. Mortar Mix ).

I thought that I waited a little after the first mix, and then re-mixed. I definitely did that when I couldn't get the first batch to go through the applicator bag -- because I emptied the bag back into the mix that I had, re-mixed it again with a little more water, and tried that. But maybe the next time that I try it, I'll try the "slake" the mortar, wait 10 minutes, then mix again, and then use.

Or, maybe regular mortar mix is more sand-like and not as smooth to work with as the Type S mortar -- which I didn't try. The funny thing is that the only reason that I didn't buy their Type S "Mason Mix" is that it comes in 80 pound bags rather than the 60 pound bags that the regular mortar comes in. I just didn't want to have to lug around 80 pound bags. If it came in smaller bags, I would have bought that instead.

[dadiOH]

Here in central Florida, it comes in 60# bags at Home Depot. Lighter but still not feather-like. That's why I use a cane :) Cane doesn't help at home though :(

They may well have more than one packaging...mine says - IIRC - "Mortar/Stucco Mix, Type S". A bit over $6.00/bag.

[nestork]

I know cement based grout needs to be mixed, slaked and then mixed again, but I've never heard you should also do that with brick mortar. I can see no reason why that would do any harm, tho.

If you find your brick mortar dries up too quickly, it's because the dry bricks are wicking moisture out of the mortar. What helps a lot is to add hydrated lime to your mortar when mixing it. The lime hangs on to water and prevents it from being wicked up by the bricks, making your mortar remain workable for a much longer period of time. Adding lime will weaken your mortar because it reduces the percentage of portland cement in it, but the hydrated lime you add ends up turning into limestone (calcium carbonate) with the passage of time, and in most cases mortar as strong as limestone is plenty strong enough for residential applications.

[TomR]

Just a quick update...., the muriatic acid worked fairly well -- kinda fun to use. I initially mixed it 50-50, meaning 1/2 water and 1/2 the 20% muriatic acid that I bought at Home Depot -- that made in about a 10% muriatic acid mixture. That was working fairly well, so I tried making it even stronger by adding more of the 20% muriatic acid and less water. That worked well too.

I wet the steps first with water, then brushed on the mixture, let it sit there and do its thing for a few minutes, the brushed it a little, then rinsed it off.

I have a little more brick pointing touch up etc. to do and I am going to re-paint the railings, but we have rain for the next 2 days, so I'll finish it after that. Then I'll post a few before, during, and after photos.