Biological growth on the stone, hard water on the glass

1 N Main Street is a commercial building in downtown Greenville, South Carolina, with a facade of precast concrete and architectural glass.

What went wrong

On the precast: staining, dirt and biological growth. That last one is the part that separates this job from ordinary soiling. Algae and similar growth are alive, they hold moisture against the concrete, and they come back from whatever is left behind, so a clean that merely lightens the surface buys a season at most.

On the glass: hard water and mineral deposits, bonded to the surface rather than sitting on it.

Two cleaners on the stone

The precast took both Stone Restore HD and Stone Restore CB2. They are not interchangeable: HD is the stronger acid-based cleaner for heavy mineral staining and efflorescence, CB2 handles the general staining and the organic growth. On a facade carrying both kinds of problem, using one alone leaves half the job done, which is why both went on here.

Two steps on the glass

The glass followed the same logic. Glass ReSurfacer Stripper first, to take off the hard water and mineral deposits, then Glass ReSurfacer Final Polish to bring the clarity back. Polish alone would eventually get there, but on deposits this heavy it is slow, and labour is the real cost on a facade.

Then the protection, which is the part that lasts

Leach Stop sealed the cleaned precast, blocking the water penetration and mineral leaching that feed the staining. Glass Defender went onto the restored glass to stop new deposits bonding to it.

Both are the same idea applied to different materials: clean the surface, then stop the mechanism that dirtied it, so the next clean is a wash rather than a restoration.