How to match mortar color for a professional finish
I have recently been looking at the front of my property and the garage needs repointing, the brickwork is exposed to the elements, which have weathered it away and it needs to be repaired.
On closer investigation, it looks like there are a couple of areas that have been re-pointed before and they don’t really match, in fact, they stick out like a sore thumb because the mortar is not the same color as the rest of the wall and it looks terrible.
Which got me thinking how do you match mortar to existing brickwork for repointing? I did some investigating and here’s what I found out:
To match mortar for repointing you need a sample of the original mortar, crush it up and separate the sand from the cement, then identify the type of sand used. Mix up mortar samples of different blends of sand and cement, 3:1 up to 6:1, let them dry on a board, and compare to the existing mix.
Following these steps will mean you can get a good color match for your brickwork but let’s look at this in more detail for a professional finish that means your repairs will blend in perfectly
Get a sample of existing mortar
To be able to match the color of your mortar, you will need to start with a sample of the mortar from the brickwork you intend to repoint or repair.
This shouldn’t be a problem as it is going to be replaced soon anyway.
Using a cold chisel and a small lump hammer carefully remove some old existing mortar from the brickwork, you need enough to see the color once it has been crushed up.
A good handful is probably enough to start with, collect it in a small plastic container, I use old Icecream containers as they are handy and easy to store.
Separate the sand
Take your mortar sample and crush it up, I put the plastic container on a solid surface like a workbench, then use my lump hammer to break down any lumps.
Once the lumps of mortar are small enough, press the head of the lump hammer into the container, a bit like using a pestle and mortar, and roll the hammer over the lumps of mortar until you are left with small grains of sand and cement.
To fully separate the sand carefully mix some Muriatic acid commonly known as patio or brick cleaner, which contains a weak hydrochloric acid mix, with water, and pour into the container over the crushed sand/cement mixture.
To mix the acid, add water to create a weak mixture of around 10:1 ie 10 parts water to 1 part acid.
I used Cementone which can be found on amazon check here for the latest prices.
Give this a careful stir and then leave the mixture for a few days. The brick cleaner will dissolve the cement or lime and leave the hard silica-based sand at the bottom of the container.
Be careful when using any Muriatic acid patio cleaner as it can burn or irritate the skin, ensure you wear the proper safety gear including gloves and eye and face protection, and always read the manufacturer’s instructions.
Once the cement is dissolved it needs to be strained from the sand. First, pour off the Acid mixture into another container, try to keep as much of the sand as possible, this should have settled at the bottom.
Then wash the remaining sand mix in clean water to dilute the brick acid. Stretch some clean old tights over an old funnel, and place that into the inlet of the container with the remaining acid placed into a bottle to act as a filter.
Carefully pour the mixture into the bottle through the filter collecting the sand. Ideally use a container that can be sealed with a lid. This can then keep the dirty mixture safe ready to be carefully disposed of following the manufacturers and HSE guidelines.
DO NOT POUR THIS DOWN YOUR DRAIN, DISPOSE OF IT PROPERLY
Identify the type of sand
Now that the sand is separated from the other components of the mortar, it’s a good idea to wash it again using clean water and leave it to dry out overnight.
Once dry the sand can be examined to see what type of particles were left behind, if there are small regular particles only it is likely to be standard building sand if there are larger stones or chips present it could well be sharp sand or a mixture.
If you need to put the sample into a clear jar with a lid and visit your local building merchant and ask to compare your sample to their stock, you can also ask if they have any information on the local area and the products used to build your home.
For older properties, this will be more difficult as suppliers change and information can be lost over time.
Check the type of Cement
The type of Cement used in the mortar mix will also affect the color, traditionally cement has a grey color and will give the mortar mix a similar coloring. The grey color is due to the levels of manganese and iron present in the cement.
Products such as White cement are available with low levels of manganese and iron which are very light in color and will give the mortar a lighter color than traditional cement.
If lime was used as the bonding agent instead of cement then the mortar will be significantly lighter in color. This may be the case on older properties as lime mortar was commonly used for building.
Hanson has a great range of cement for all-purposes take a look here
Mix some mortar samples
The next step is to make up some samples of mortar. If you have been able to identify the base components used then you will only need a few samples to match to your existing mortar.
If finding the right base components was a problem or you don’t have the time to investigate, you can create more samples at this stage and still get a good match for your mortar.
Firstly you will need some aggregates to work with, a single bag of sand and cement will be plenty if you need to buy one of each type, this becomes a bit more expensive, but typically a bag of sand or cement is only a few bucks.
You will need a clean dry board, I used a 1m x 1m piece of hardboard but any spare flat dry surface that you can write on will do.
Take a piece of paper and write out which mixtures you intend to make up:
give each mixture a number, then write the corresponding number onto the board and leave around 100mm between each, this is where you will put the sample once it is mixed.
I found it easier to divide the board into 100mm (4”) squares using a marker pen and give each square a number that corresponds to the sample mixture.
To mix the samples, I used a small plastic ice cream tub to mix the mortar samples in and a medicine mixture cup, the kind you get with a bottle of a cough mixture, to measure out the equal parts, but any small container will do so long as you keep the ratios the same.
Put the sand in first and then the cement as you would if mixing a full batch, this is better because the cement will mix more evenly into the sand.
Putting the cement in before the sand means the sand will swamp it and the cement will be left on the bottom of the container making it more difficult to mix properly.
Mix the dry cement and sand together well to get a thorough, even mixture. There should be no lumps or unmixed cement
Carefully add water to the mix, do this sparingly as the sand will absorb a lot and it is easy to make the mortar too sloppy. I nearly got caught out the first time I mixed a small batch.
The mortar should be a creamy consistency, thick enough to stand to a peak but wet enough to just slide off the spoon.
Once the mortar sample is mixed place it on the board in the square with the corresponding number.
Then it’s a case of rinse and repeat, give the containers a good wipe down, and then add the sand and cement for the next mixture on the list, working your way through each one.
Compare mortar samples
Once you have mixed up all of your mortar samples and placed them on the hardboard let them dry off for at least 24 hours, if your samples are bigger than a small handful they may need longer to dry off.
At this point it’s a good idea to take a photo of the samples, make sure you have a camera with a good resolution, most new smartphones are good enough.
Take the samples outside during the day to get good light and take a photo of the whole board and then an image of each square individually, ensuring the number can be clearly seen on the picture,
Keeping a good record like this means you can reuse the images over and over again.
But nothing is as good as the real thing and now you can compare the new mortar color samples directly against the mortar of your wall.
Just remember to take one at a time to avoid mixing them up in the wrong place.
Mortar Plasticizer and Mortar dyes
As if the different sand and cement or lime combinations weren’t enough, if you struggle to find the right color for your mortar there are other options like mortar additives that can change the color.
Mortar Plasticizer comes in a liquid form and can have different color options so that when a few drops are added to the mortar mix they will affect the color of the mortar.
This is used to help keep the mortar flexible and workable whilst bricklaying, older less orthodox techniques included using washing up liquid as a plasticizer, but I would not recommend that.
For special colors like black, red, or white and pretty much any color in between, there are an array of mortar dyes and pigments available and mean that mortar color options are endless.
The mortar dyes can be dry pigments that are added to the mortar during the mixing process or brush on tints that are painted on once the brickwork has been built.
If you have come this far and not been able to match the mortar color then there are specialist services that will do this for you, they come at a price but if you want to match your existing mortar color they may be a final option.
Getting the right match for the color of your mortar before you carry out repointing or building new brickwork can be a time-consuming process, but putting in the effort and getting it right is worth it so that your pointing and mortar matches the surrounding areas and blends in for a professional finish.
Matching Replacements for Cracked bricks
If you need to replace bricks that have cracked, chipped, or spalled over time then that is another job that needs to be addressed before actually cutting into your existing brickwork. Read our post on how to match bricks.
This article was written by: Richard Quinton – The DIY Help Desk Owner, Engineer & technical specialist.
Richard is one of the key partners in The DIY Help Desk team. He is a qualified Engineer, writer, and publisher, educated to Master’s level. He is a keen advocate of DIY and home improvements.
Richard enjoys helping others to learn new skills and reach their goals and believes that passing his knowledge and experience on through his writing is an effective way to positively impact the lifestyles and well-being of others on a larger scale.