How and why efflorescence occur on facing brick wall | Final Part

Two week ago we made a description of the various types of efflorescence damages depending on the different manners that efflorescence manifest themselves. A brief description of these categories are given here as a reminder.


These damages some times only affect the aesthetic component of the façade, were divided into four categories as follow.


Category 1: Salts which are deposited on the brick surface, highly soluble in water, of whitish, appearance. They usually appear in the top quarter of the buildings as this part is often more exposed, at the base of the wall and around window sills.

Category 2: Criptoefflorescence’s, can be determine to have happen when we see large areas of bricks that have chipped off or major amounts of bricks that have tended to opened up in layers by as much as few millimetres.

Category 3: When we can observe dark brown or black spots appearing on the bricks (usually brown pigmented type) and on the mortar joints.

Category 4: When we can distinguish spots of greenish-yellow. This kind is very rare, so rare that in fact, I have never seen any in Spain. On this final part of “How and why efflorescence occurs on facing brick wall” we will specify the remedy to cure these defects.

Depending on the type of efflorescence, the treatment to eliminate it is:

For category 1: This type of efflorescence disappears after several cycles of wetting and drying, but to make it disappear faster, you can repeat the process of brushing the surface with a stiff non-metallic brush and then wash off the rests with clean water. If the whitish stains persist, it would advisable to wet thoroughly the façade once again and apply water with hydrochloric acid solution up to a 10% and then wash off with clean water.

For category 2: In this case, there is a slow circulation of water through the capillary network within the brickwork with a strong evaporation action, resulting in increased pressure which causes the brickwork to peel or crack. To prevent its occurrence, there is the need to deeply irrigate the entire brick wall repeatedly during periods of low evaporation i.e. not in summer periods.

For category 3: Such stains are not removed permanently easily. If there are abundant deposits it is necessary to brush or scrape frequently, soaking up with water and then applied a solution of hydrochloric acid, after which, rinse abundantly. Repeat the application of hydrochloric acid as many times as it is necessary. Watch out not to use a high concentrated solutions which would be detrimental to the material. The best method is to do a small portion of brick work in a discreet position of the wall, if works well then treat the rest of the brick work the same.

For category 4: To remove these disagreeable stains, apply a paste consisting of sodium citrate, warm water, glycerine and chalk power, it should be rinsed with clean water after each application, the process could be repeated until its total elimination.

There are other stains provoked by efflorescence which could appear on brickwork and could be removed by using chemical solutions.

The appearances of greenish-yellow spots are extremely rare. If found it can be solved by applying a solution of caustic soda of a proportion of 350 grams per litre, leaving it to act.

There is one last type of efflorescence which is the case of dark brown or black spots, that appear on the bricks usually brown pigmented bricks and also on their mortar joints. They are differentiated from category 4 because the colour of brick is obtained by the use of manganese dioxide.


This category is best solved by moistening with water the smudged area, then apply a solution of acetic acid, hydrogen peroxide and water. For light stains, dilute 2-3 times the previous solution, it is applied and washed abundantly with caustic soda.

I have to be adamant here and say that great care should be taken when using chemicals. I strongly recommend the use of protection clothing and safety paraphernalia such as eye protection glasses etc. Read carefully all the instruction given by the manufacturer and also obtain the recommendation of a professional before you apply any of the above solution since the type of efflorescence are varied and often it is complicated to identify the correct type. Some times, depending on the extension of brick wall it may be worth to obtain the help of a specialize laboratory to obtain the correct diagnose before applying any of the above solution.

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