When building a stone structure using mortar, cement often splashes on the stone, staining it and making it look unattractive. In this article, we will be discussing several methods of cleaning this mortar/cement off without damaging your stone.
How to Clean Cement off Stone?
Not all stone surfaces are the same. For instance, Marble and granite are different from Indian sandstone. So, we’ll look at different methods to clean cement from various types of Stone surfaces.
Cleaning Cement off Indian Sandstone
Although Muriatic aid may be the choice for many for cleaning cement off sandstone this acid might damage the integrity of the whole surface doing more harm than good. We’ll use White Vinegar for this method. Though it is weak and may take a while before it works, it is safe on your stone and will not leave discolorations.
1- Safety goggles
2- White vinegar
4- Nose mask
5- Putty knife
7- Spray bottle
8- Pressure washer
STEP 1- Wear safety goggles and a nose mask to protect yourself from the flying cement dust that will come off your stone.
STEP 2- Take a scraper or a putty knife and gently scrape large bits of mortar on the Indian sandstone. This makes it easier to clean the sandstone and get rid of all stains or residues.
Caution: Be careful not to harm yourself while doing this. If you apply too much pressure and the mortar suddenly comes off, it can catch you off-guard and unbalance you. Also, ensure that you do not chip the stone or damage it in any way while scraping the mortar off.
STEP 3- Set your pressure washer on a low setting to avoid damaging your stone and use a medium-sized nozzle. Gently pressure wash all the areas affected by cement splashes.
Don’t keep the pressure washer on a single spot for too long and don’t keep it on the mortar between the stones.
By now most of the stains would have started to disappear. But to ensure that all the mortar residue is cleaned off your sandstone, you should use white vinegar.
STEP 4- Mix 1 part water with 1 part vinegar in a bowl. Pour this solution into a spray bottle and spray your sandstone thoroughly with it. You should only spray the areas that are still stained with mortar. If the stains are still thick and very visible, you can use undiluted vinegar.
STEP 5- Let the vinegar solution sit on your sandstone for about 2 minutes. Any longer than that and the acid could begin to damage your sandstone.
STEP 6- Scrub the mortar stains with a stiff-bristled brush. The stains will come off easily as you scrub but don’t use too much pressure.
STEP 7- Rinse the sandstone using a garden hose or use a bucket and bowl.
Cleaning Cement off Granite, Limestone, Marble, Travertine
Natural stones are susceptible to damage by acidic cleaners and those containing bleach. But if you use these cleaners as a last resort, don’t let them sit for too long.
Even vinegar is mildly acidic in nature and that can also cause etching on the natural stone surfaces.
Hydrogen peroxide is a great cleaner for natural stones like granite because it is gentle and will not etch or damage them in any way.
1st Method (Hydrogen Peroxide)
1- Safety goggles
2- Nose mask
4- Hydrogen peroxide
STEP 1- Wear a nose mask to avoid breathing in cement dust and use safety goggles to prevent cement dust from entering your eyes.
STEP 2- Scrape large pieces of mortar from your natural stone with a scraper or putty knife. If you don’t do this, the hydrogen peroxide will spend more time trying to penetrate the mortar to clean the stone. Be careful not to hurt yourself.
If some areas prove too stubborn and aren’t budging, use a hammer and a chisel to get better results. But try not to chip your stone or damage it.
STEP 3- Use fine or extra fine grit sandpaper to sand down the mortar residues that are too small to scrape but still bulky on the stone. Sand these areas until only a stain or film of mortar remains on your natural stone. This may take a lot of time but it is worth the effort.
STEP 4- Now mix 1 part hydrogen peroxide with 1 part water in a bucket.
STEP 5- Use a stiff-bristled brush to apply the hydrogen peroxide solution onto your stone. Apply it on the areas with mortar stains or residue.
As you apply the solution to the stone, scrub it firmly but gently to get rid of the cement stains. Don’t scrub the mortar between the stones.
STEP 6- Let the solution sit on the stone for about 5 minutes. Then scrub it again with hydrogen peroxide.
STEP 7- After the second round of the solution application and scrubbing, rinse the stone with fresh water.
2nd Method (Ammonia)
3- Safety goggles
5- Nose mask
7- Dish soap
STEP 1- Chipping off pieces of mortar from your stone will produce some cement dust so wear safety goggles and a nose mask before you start. Wear rubber gloves to protect your skin since you’ll be working with a chemical.
STEP 2- Get as many mortar pieces off your stone as you can, using a scraper. You may need to use a small hammer and chisel if the mortar has been on the stone for a long time and become stuck.
STEP 3- Pour 1 cup of ammonia into 1 gallon of water and mix it thoroughly in a bucket. If the mortar has been on the stone for a long time and other methods haven’t worked, you can use 1 1/2 cups of ammonia or 2.
STEP 4- Use a brush to apply the ammonia solution to mortar stains on the stone. Apply the solution without scrubbing the stone.
STEP 5- Let the solution sit on your stone for about 5 minutes. This is enough time for the ammonia to react with the mortar residue, breaking it down, and making it easier to clean it off the stone.
STEP 6- Scrub the stone with a stiff-bristled brush. You can dip the brush into the ammonia solution as you scrub. This gives the brush more cleaning power to get the job done.
STEP 7- Rinse the stone surface with enough water. To get rid of the ammonia solution, you can put a few drops of dish soap into the water. Use the soapy water to first rinse your stone, then follow it with fresh water.
Cleaning Cement off Flagstone
Before using muriatic acid on your flagstone to clean off the mortar stains, ensure the mortar between the stones has been cured. If not, the muriatic acid will eat into it.
1- Muriatic acid
4- Safety goggles
5- Nose mask
6- Rubber gloves
7- Garden hose
STEP 1- Muriatic acid is a powerful chemical that can harm you if not handled with care. So you need to wear acid-resistant rubber gloves, safety goggles, long sleeve shirt, pants, and a nose mask.
STEP 2- Wet the flagstone with water thoroughly. You can use a bowl to pour water on it (if the area is small) or use a garden hose to make the process faster.
If you use muriatic acid on your flagstone without first wetting it, it will damage it. Yellowish-green stains will appear on the stone when it dries.
STEP 3- Pour a gallon of water into a plastic bucket and add 1 cup of muriatic acid. Mix it thoroughly with a long plastic or wooden spoon. If the mortar has spent a long time on the flagstone and it is caked on it, you need a stronger solution. Mix 1 part acid with 10 parts water.
Always pour acid into water and not the other way around.
STEP 4- Use a brush to apply the muriatic acid to the cement/mortar stains on the flagstone. Apply it generously! The mortar will begin to bubble as the muriatic acid eats into it.
STEP 5- Let the muriatic acid sit on the flagstone for about 3 minutes. This will give it enough time to dissolve the cement.
STEP 6- Scrub the flagstone with a stiff-bristled brush until you get the mortar stains out of it. If you need to apply more muriatic acid as you scrub, feel free to do it.
STEP 7- Rinse the flagstone using a garden hose or simply pour enough water on the surface if you don’t have access to a hose.
STEP 8- If you have plants around the flagstone, then you need to neutralize the muriatic acid. Mix 1 cup of ammonia with 1 gallon of water and use it to rinse the area.
Cement (whether spilled or in the form of dust) can be pretty ugly. Not all cleaners work the same way and not all cleaners work for all kinds of stone. Sandstone, flagstone, and natural stones will require different methods to clean cement off them.