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What is Black Efflorescence

Also known as Desert varnish or Black attack.

Black Efflorescence is the unpredictable sporadic darkening of concrete, clay and natural stone. It usually occurs within six months of installation and is not easily removed either with solvents or by physical means. This phenomenon is all around us. It might occur on pavers, bridges and buildings.

Many studies have been conducted and the precise cause of this phenomenon is still not well understood. It has been found however that there does seem to be a correlation between black efflorescence and the moisture of the installed area. In the short term the only solution is to replace the affected pavers and ensure adequate drainage of the sub base during installation.

Over time and as the pavers wear the discolouration might fade and blending with other pavers will improve. There are other kinds of discolouration that could be mistaken for black efflorescence namely: Mold, algae, tyre rubber and staining from bedding sand.

The formation of efflorescence on a site (black and white) is linked to the earth’s water content  beneath the paving. In areas where high water tables exist or where moist clay soils are prevalent, efflorescence is usually a common occurrence. Black efflorescence is usually common to specific geographical areas. A neighbour’s paving and adjacent concrete structures would give you an indication of the potential of your paving being affected by efflorescence.

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Cnr Cresset and Musket Roads
Midrand Industrial Park
Phone: 011 310 1176
Email: info@bosun.co.za