Surface PreparationEfflorescence from brick and stone
So what is “efflorescence”? Simply put, it’s that salty looking stuff you often see on brickwork. It often occurs on masonry construction, particularly brick when water is moving through, or driven out as a result of the heat of hydration, brings salts to the surface that are not commonly bound as part of the cement stone.
As the water evaporates, it leaves the salt behind, which forms a white, fluffy deposit. The resulting white deposits are referred to as "efflorescence" or "saltpetering." This can sometimes be brushed off, but it can also leave stubborn stains. Pressure washing (water) does not remove it – in fact it often will make it worse, as it re-introduces water into the brick. The common method for removing it is an application of phosphoric acid, rinsed off with a mild detergent. Of course, this is NOT environmentally friendly as it compromises flora and fauna, and can get into the sewer system. In the city of Calgary this will result in large fines if a bylaw officer happens to come by.
Dry ice blasting works because it does not introduce water into the surface – and it’s a chemical free, environmentally friendly alternative.