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Why Do Bricks Go White?
The white marks on bricks are caused by salt. When bricks get wet, the salt inside the brick dissolves and leaches through to the surface. Bricks turn white when this water evaporates, leaving salt deposits on the brick face. This process is known as efflorescence and is a common problem.
Every time this process repeats itself, another layer of salt will form. This is why some older bricks have a thick, fluffy white layer that can be harder to remove. Facing bricks are particularly susceptible to efflorescence as they are constantly exposed to wet weather.
When efflorescence is present, bricks are also likely to suffer from spalling, which can be much more serious.
Is Efflorescence On Bricks a Problem?
Efflorescence on external bricks is not something you should worry about. It is a natural occurrence and is to be expected on porous facing bricks, exposed to the elements. However, if white marks are present on internal brickwork, this is an area of concern and should be investigated immediately to avoid further complications.
Internal bricks do not come into contact with rain and snow, so should not have been penetrated by water, which would bring salt to the surface. Internal efflorescence, therefore, is a sign of damp inside the home.
If the source of the moisture is not identified and treated, then structural problems may arise as your bricks degrade over time. Internal damp can also lead to black mould, which can cause respiratory issues.
Contact a qualified damp expert if you think your home may have a problem.
How to Remove Efflorescence From Bricks
There are four ways to get rid of efflorescence. You can clean them with a firm bristled brush, a vinegar solution, a pressure washer, or a chemical solution designed specifically for efflorescence removal.
1. Firm brush
If your bricks have a smooth face, you may be able to clear the white marks using only a brush. Hard bristles can loosen and dislodge salt crystals if the white marks are relatively new.
It is more labour intensive than the other methods but is also the only one that does not involve wetting the bricks. Increasing moisture levels has the potential to encourage future efflorescence.
Wear a face mask when scrubbing as airborne salts can cause irritation.
2. Vinegar solution
Bricks that have stubborn efflorescence can be removed using a vinegar solution. The natural acid in the vinegar helps to break down the salt, making it easier to clean.
Mix one part vinegar with one part water to create the cleaning solution. Spray it onto the face of the brick covered by efflorescence and leave to soak for at least five minutes. Respray after the time has elapsed and scrub with a stiff-bristled brush.
If you are cleaning old bricks, this method may not be suitable as vinegar may be too abrasive.
3. Pressure washer
One of the easiest ways to clean bricks is using a pressure washer. Use a setting or nozzle that will be powerful enough to remove the marks, but not so powerful that it could damage the brick.
It is important you do this during a spell of warm weather so that the bricks dry out quickly. If they are damp for too long, efflorescence will return.
4. Specialist brick cleaning solution
The toughest efflorescence will need a specialist brick cleaner that can dissolve salt crystals. Before applying the brick cleaner, scrub the surface with a brush to clear any loose dirt. Then, wet the surface of the brick and apply the solution. Wait 10 minutes for it to take effect before washing it away.
Repeat this process if any white marks remain. We would advise that you test the cleaner on a brick that is out of sight to see how the solution reacts with the surface.
Do not use cleaners that contain muriatic acid. If the mix is too concentrated it can damage the face.
Why Does Efflorescence Keep Coming Back?
Even after a thorough clean, efflorescence will keep coming back as long as there is still salt inside the brick. It is not a one-time occurrence and could continue for years unless the brick is treated. It will not go away on its own.
Another reason for the sudden recurrence is that the brick has not dried properly after being cleaned using a pressure washer. Salt deposits can linger if the water was allowed to sit on the surface. To avoid this, clean the white marks on a warm, sunny day so the bricks will dry quickly.
How to Stop Efflorescence Coming Back
The best way to stop efflorescence from coming back is to apply a brick sealant. This will prevent water from penetrating porous house bricks and drawing the salt to the surface. This addresses the source of the problem and is, therefore, a more effective and permanent solution compared to frequent cleaning.
For sealants to be effective, there are a number of best practices to follow.
First of all, new facing bricks should not be sealed. Many housebuilders store bricks on-site, exposed to wet weather. This means they are likely to contain high levels of moisture when new. By leaving your house to settle for at least a year, excess moisture will escape and not be trapped by applying a seal.
If your home is not new, the next step is to clean away any existing efflorescence. You should never seal over efflorescence as it will trap the salt crystals underneath the sealant. This would make removing the white marks much more difficult in future, as the seal would need to be stripped.
After cleaning your bricks, they should be given enough time to dry before applying the sealant. For this reason, it is better to clean and seal bricks in the summer, so that there is no residual moisture that could be trapped.
Once the bricks are dry, it is time to seal them. Many sealants only require one coat for effective protection against rain, damp, and frost. They will also improve the life of buildings and prevent the growth of moss and algae.