PLEASE DO NOT ADD WATER to muriatic acid, hydrochloric acid, or any strong
acid. A VIOLENT reaction will occur.
It is safe to add acid to water, slowly, but not the reverse.
Remove Brick Mortar
Summary: Cleaning mortar off bricks is a common problem. Brick mortar can be taken off bricks using an acid. Use care when cleaning brick on your project.
DEAR TIM: How can I remove brick mortar from the sidewalk I just constructed with paver bricks? My husband and I got the mortar smeared on the brick, and it looks terrible. What methods can I use so the brick is not damaged? Is there a non-toxic way to do this repair? Sarah H., Kingsport, TN
DEAR SARAH: Smeared mortar on brick pavers, as well as brick walls, is a very common problem. Depending upon the type of brick, the job can be simple or a nightmare. It is my hope that you do not have a deeply grooved wire-cut brick, as these have many small crevices that can make cleaning a career choice.
Since you are concerned about the toxicity of different options, you may find it very hard to do this job. You can use certain acids that are more aggressive than others, and the ones that work faster tend to be more toxic. But don't panic as you may discover that an aggressive acid treatment may work for you if you work to control the amount of liquid used as you work.
Mortar is smeared on the brick. It is not that hard to remove if it is thin. PHOTO CREDIT: Tim Carter
There are other acids that will react and dissolve the alkaline chemicals in the mortar. Even white vinegar that is in your kitchen will work to some degree. Since you eat vinegar in many foods, you know it is not a toxic acid. The challenge for you is finding an acid somewhere between vinegar and hydrochloric acid that will efficiently remove the mortar buildup. You should consider calling a physical chemistry professor at a local college or high school. You can also visit a building supply company to see if they stock a non-toxic acid that will dissolve the mortar.
The first step in the process is to remove as much of the mortar as possible with a scraper or chisel without scratching the brick face. Clear water flowing over the brick acts as an effective lubricant that will minimize damage to the brick. If you have to tap the scraper with a hammer, do so at a low angle with the face of the scraper nearly parallel with the face of the brick. You are trying to get the mortar film to a thickness less than that of a plastic credit card.
Once the majority of the mortar is off the brick, you then should consider bathing the brick with a diluted acid solution. As mentioned before, muriatic acid is highly effective, and it works on most brick. Usually you mix one part of the acid with ten parts of clean water. Always read the instructions on the acid label and pay particular attention to all safety instructions.
It is also a good idea to contact the manufacturer of the brick. Some brick can be damaged and discolored by acids. It is really worth the effort to call the brick manufacturer if possible.
I have found in most cases you should dampen the brick with clear water before you apply the acid solution. Always try this in an out-of-the-way area if you are unsure if the acid will harm the brick. If you use muriatic acid, you should see tiny bubbles forming where the solution contacts the smeared mortar. This tells you that the acid is reacting with the mortar paste and is starting to dissolve it into the liquid solution.
Use a scrub brush to help remove the mortar. Wait five or ten minutes after the acid solution has been applied to the brick before you scrub. Allow the acid to do much of the work for you. It can take multiple applications of acid solution to remove all of the mortar. Rinse the acid solution from the brick with massive amounts of water. The more water you use, the better.
Working with acid solutions is very tricky. You can hurt yourself, your clothes, your brick, the new mortar and vegetation around your home. If you have valuable vegetation and landscaping, you should try to stop any acid solution from getting into the soil.
Be sure to wear all of the protective gear to prevent burns to your skin and eyes. Muriatic acid straight from the bottle is a wicked liquid. The fumes are very toxic, and it can cause serious burns to your skin very quickly. Do not underestimate this chemical.
I would not ever use muriatic acid on fresh mortar. Allow the mortar to cure a minimum of two weeks before you attempt to acid wash it. That said, if you get mortar on brick you should immediately try to scrape it off or brush it off. If there is a thin mortar paste that has no sand in it, that will easily and quickly be removed with mild acids like vinegar. Harsh acids will attack the fresh mortar between the brick that you do not want to remove.
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Comments:
Gary Brown 30 Jul 2008, 20:34
poleclimber 27 Mar 2009, 18:20
My brick has faded from the sun.Is there a wash to rejuvinate the color
of the brick? Thankyou,poleclimber.
BGarrett 29 May 2009, 19:41
I removed a brick wall on my patio that was against my brick house. It
left motar on the brick of coarse. The cleaning procedure you gave for
removing fresh motar, would it work on motar that has been on for years?
Gary Brown 30 May 2009, 09:18
It probably will work, but it could take many applications. Mortar is
basically cement and water, without the aggregate (gravel). As it cures,
it loses moisture and becomes stone-like concrete. The harder it is, the
more difficult to remove.
As Tim said above, take off as much as you can with a scraper or a chisel. Muriatic acid will remove the remainder. Read the comment above on how to dilute it safely; it can be applied full strength. Wear eye protection, long sleeves and rubber gloves. Don't breathe the vapor. Brush it on with a cheap paint brush, let it soak till it stops foaming, and rinse. Be careful - the rinse water will kill vegetation.
Elizabeth 06 Jul 2009, 17:42
I'm confused about whether to dilute or not. Tim Carter's instructions say
to "mix one part of the acid with ten parts of clean water" while Gary
Brown's comment says that adding water will create a violent reaction. The
label on the bottle of hydrochloric acid I purchased is equally
contradictory.
Gary Brown 06 Jul 2009, 18:56
What I said was, you can add acid to water, but not water to acid. Learned
that in high school chemistry. "Acid to water will not get hotter."
When you pour acid into water, you're making a very dilute acidic solution. But if you add water to acid, it is a very strong solution - will probably boil or spray, like opening a can of warm beer! That stuff will blind you if it gets in your eyes, will kill you, will disfigure you if it gets on your skin, and the vapor will destroy your lungs. IF you're going to dilute it (I don't, because the weaker solution takes much longer to do its work), dilute it by adding the acid to water. NOT the other way around! If using it full strength, use it on a slightly breezy day and try to stay up-wind. Get kids and pets far from the area. Wear eye protection, long sleeves, rubber gloves and rubber boots. Good advice, but honestly, I've never used them, and the worst thing that has happened to me is severe coughing when I unavoidedly breathed the fumes. If the acid gets on painted parts of the house or on vegetation, kiss it goodbye. If you accidentally get any on yourself, your clothes, etc., strip them off immediately. Don't track it into the house, where it will ruin almost anything you touch or walk on. Just strip naked right there and spray yourself down with a garden hose. Have the hose ready before using the acid, by the way. While we're on the subject, acid removes mortar because mortar contains lime (calcium) which is alkaline (the opposite of acidic). The two neutralize each other, but while they are reacting, there will be a lot of foaming and fumes. Leave the acid on until the foaming stops, then rinse with water. Water, on the other hand, does not neutralize acid, it only dilutes it. It's not likely your bricks contain much lime - they are made of baked clay, so the acid probably won't have any noticeable effect on brick. However, concrete and concrete blocks DO contain a significant amount of lime, therefore the acid will readily damage them. I hope this helps. Gary
ray 29 Aug 2009, 11:37
the mortar is smeard on the brick
not caked on , so please dont use a hammer and a chiesel , and yes you can use moratic acid and water but on red brick they recomend you dont do that , i would suggest if soap and water cant get it off then try a little bit of martic acid and water mixed ( not to heavy where only talking about one brick paver here ) if this still doesnt work and it is still bothering you take a ginder cut it out and turn it over , next time you place the mortar in the joints be more careful what untill it gets thumb print hard then joint it and brush it off ( thumb print hard though ) after after you brush it off joint it one more time
Scott 26 Oct 2009, 09:58
Excellent advice Gary!
I just replaced about 80 pavers on my sidewalk that had come loose over the years. I mixed the mortar with minimal water so it was a peanut butter consistency and had virtually no cleanup at all. Any mortar that was left on the surface was easily brushed off once dry. There were a few areas where I had stepped on the wet mortar requiring some cleanup. I found a 1:1 acid to water mixture worked well. After a few minutes I scrubbed with a stiff plastic brush (don't use a natural bristle brush) on a pole then rinsed. Usually 2 or 3 times will remove thin mortar smears. You can use a wide brick chisel to help loosen thicker mortar smears instead of a brush. Be sure not to let any metal tools sit in the acid solution. - Scott.
Jenifer Carter 20 Nov 2009, 14:25
We had a natural stone walkway put in about a month ago... contractor left
1-inch ring of grout film around every last stone, so we're getting ready
to clean, then seal. Assuming we have to use muriatic acid... is it safe
on natural stone? Do we carefully have to apply the acid only to the
excess on each stone, or can we apply broadly, scrub the stone and then
rinse off without damaging the grout between the stones?
Gary Brown 23 Nov 2009, 20:12
Hey, Jenifer, I'm frustrated because I had written a long, helpful
(hopefully!) reply to your question, and somehow it got discarded when I
guessed at the security thing incorrectly!
This time, I'll copy it before guessing at the security thing. First, I suggest you send a certified letter to the contractor, asking when he will remove the grout stain. Intimidate him a little, it might work. It's PROBABLY safe on natural stone, but it depends upon what minerals are in the stone. If there's much lime, you probably shouldn't use it. Are there any leftover pieces around that you could experiment with? You should only apply acid to the grout you want to remove. Pour a small quantity into a plastic container and brush it on using a cheap brush (but I bet the foam ones will disintegrate immediately on contact with the acid). Also, what's under the walkway? Gravel only, or is there a plastic weed barrier? I don't know for sure, but I imagine that the barrier could hold the acid (even after the H2O has evaporated, the residual salt is still acidic) for a very long time - and even might revert to liquid acid after a heavy rain. Not a good idea for bare feet, nor for barefooted pets. Bottom line, don't flood the area with acid. Only use as much as you must use. Nothing you do will avoid very slight damage to the grout between the stones. But the good news is, if you're only removing 1/64 of an inch of grout from the stones, it also should only remove 1/64" from the "good" grout. Good luck, and I'd like to know what results you have. As I said above, a reputable contractor should take care of this for you. The longer the grout sits, the more it cures (hardens), so this is not something you want to postpone. If you must do it yourself, I can't stress enough the need for protective gloves, goggles, etc. Don't have dangling sleeves, etc., that could get wet then rub against your body. Don't breathe the fumes! Be sure to seal the grout after cleaning off the excess. Gary View all comments |
