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.
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 them with the acid.
Wait about 7 days before washing the brickwork down.
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.
Wet the wall down with water.
Use a very stiff brush to apply the acid solution.
Do not use a wirebrush, 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. (keep, the bricks clean when you lay them)
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.
The acid will neutralize in contact with moisture.
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)
There is a product on the market in Australia called Anti Eff, it is made specifically for cleaning concrete masonry.
Brickwork.net.au
Acid washing brickwork