Cleaning of Brickwork
Good bricklaying and effective protective measures will minimise the need for cleaning when a project is completed. However, no matter how careful the workmanship, there will usually be some requirement for removing mortar stains before a building can be handed over. If mortar stains are to be removed using proprietary cleaners, it is advisable that a small trial area. Incorrect application of acids washes over large areas of brickwork can ruin the appearance rather than improving it.

Apart from site spillages (which are not covered here) there are three main types of brickwork staining. While it's important to be able to distinguish them it's also very important to understand that all are caused by letting the bricks become wet either in storage or during construction. Bricks or brickwork not protected from rain will show staining of one of the three kinds. This is not a fault in the brick but a fault in the working methods. Proper site storage of the bricks and covering wallheads during construction will go a long way to avoiding staining.

Efflorescence
Efflorescence occurs when bricks are allowed to become saturated. Soluble salts within the brick are dissolved and migrate to the surface. As the water evaporates the salts crystallise and show on the surface as a white deposit. Efflorescence is temporary and harmless. It can be washed off with water
or, in time, rain will wash the soluble salts away leaving the brickwork clean. It's important to distinguish between efflorescence and other forms of
staining such as lime staining, inappropriate treatment of efflorescence (eg
as if it was lime staining) can make matters worse. If bricks are stored "dry", ie clear of the ground and covered to protect them from rain during
construction, efflorescence will be reduced markedly.

Lime staining
Lime staining appears similar to efflorescence and, although the root causes are similar, the substances involved and therefore the treatment are very different. Lime staining occurs when the brickwork is saturated - again either from poor storage, lack of protection during construction or by ground water flowing through the walls, for example in retaining walls. Here the problem is caused by free lime in the mortar or salts in the cement. The mechanism is similar to efflorescence in that the lime (Calcium Hydroxide) migrates to the surface in solution and is deposited on the brickwork, but here the similarity ends. Calcium Hydroxide reacts with Carbon Dioxide in the air to form Calcium
Carbonate which is insoluble in water and therefore will not wash off easily.
Fresh deposits can be brushed off the brickwork but if the lime is allowed to
react with the carbon dioxide then an acid treatment may be necessary.
Good "dry" storage and protection during building will help to avoid lime staining.

Iron staining
Iron staining is used as a catch-all term for the rare occurrence of staining from metallic salts in the clay.  While it is usually caused by iron ions it can also be due to manganese, chromium or vanadium. Because these salts are not very soluble, the problem of iron staining only occurs when brick have been totally saturated over a long period of time. Good site practice with
"dry" storage and wallhead protection will help avoid iron staining.