Acid Washing

Brick washing with acid.

Extreme caution should be used when using acid to wash down brickwork.
Eye protection and gloves must be used.
Avoid breathing the fumes at all costs.

If you are unsure about using acid then dont use it.
Get a professional brick cleaner to do it for you.
There are plenty of brick cleaners to choose from in the Yellow Pages.


Keep it clean as you work.
Every effort should be used to get the brickwork clean before you use acid.
You should be scratching and brushing any fresh mortar off the bricks as you lay them.
The cleaner that you can leave the brickwork when laying prior to using acid, the easier it will be to wash with the acid.
Wait about 7 days after laying before washing the brickwork down.

Mixing

Brickwork is washed down with Hydrochloric Acid at a ratio of 10 parts water to 1 part acid, the acid is always added to the water.

Hydrochloric Acid is also known as Spirits of Salts.
When you have finished off your brickwork it will be necessary to wash it down with the acid solution to remove the smear marks the mortar leaves on the face of the bricks.

Applying

Wet the wall down with water.
Use a very stiff brush to apply the acid solution.
Do not use a wire brush, the wire brush will dissolve in the acid and may leave "metal" marks on the bricks.
You will see the mortar smears start to fizz as you apply the acid solution, this is normal.

Leave the acid to do its work for a minute or two then scrub off with the stiff brush.
You may have to re-apply the solution more than once, it all depends on the amount of mortar that is on the brickwork.
If there are thick bits of mortar on the wall, you may have to use a scraper of some kind, a piece of brick sometimes works well as a scraper.

When you think the wall is clean enough wash it all down with water, this will help dilute the remaining acid on the brickwork.

A second application may be needed to get the bricks really clean.

Some types of bricks will discolour when washed with Hydrochloric Acid.

If you are unsure contact the brick manufacturer.
Usually the white Sand/Lime bricks will discolour with acid, and also some concrete bricks and blocks. (They tend to go GREEN)
Its the Vanadium that is present in the brick that turns green.


There is a product on the market in Australia called Anti Eff (cache), it is made specifically for cleaning concrete masonry.

Here are some clay bricks I came across that have been wrongly cleaned, they have also turned green.
The acid water mix must have been far too strong, because it has badly etched and eroded the mortar joints.
I see badly eroded mortar joints all the time, due to either the pressure washer nozzle being too close to the brickwork, or because the acid is too strong, or probably both.

More bad cleaning.

These bricks have been subjected to an acid solution that was far too strong, brick cleaners apply a strong solution to save themselves time but ruin the brickwork in the process.
The bricks have turned orange due to Iron Oxide in the brick reacting with the acid, it can occur in patches (as in the photos) or affect the whole wall.
















The bricks below are how they should look for colour, even after acid washing.

Boral How to Clean Brickwork.

http://www.boral.com.au/claybricks/Brick_Cleaning_Sheet.pdf

The sheet from Boral describes the discolouration as mentioned above.

Vinegar.

Vinegar can be used when the mortar smear is very light, use white vinegar straight from the bottle.
Apply the same way as for acid.