Buildings with precast concrete façades are inherently susceptible to window staining. At Park Plaza II, the building’s windows were designed to be installed flush with the precast concrete façade. This condition allows rainwater to wash across the windows and deposit minerals from the precast onto the glass surfaces. These minerals will then embed themselves within the pores of the glass, which causes staining that cannot be removed without more aggressive techniques.
Removing these tenacious stains caused by mineral runoff, without creating scratches or causing etching to the
glass surface, is complicated by many factors. These factors include direct sunlight, temperature of the glass surface, humidity levels, available access equipment, and trained workers in this craft. Every building, and often each elevation of a building, may require distinct approaches to glass restoration. Park Plaza II was no exception to the rule.
After performing a live test demonstration for client approval, Valcourt’s crew was able to develop a technique that would remove the window stains without either etching or scratching the glass surfaces. The technique first involved determining how to remove the hardened, outermost crystals of the mineral stain. The next step involved a buffing process to eliminate the portion of the stain that embedded itself into the pores of the glass. A minimally abrasive, non-acidic compound was used with an electric buffing wheel—at a low rpm to reduce the chance of scratching the glass surface—to agitate and remove the stain.
Valcourt was successful in restoring the windows to the same level of optical clarity as if the windows were new again. The client is extremely pleased with the dramatic improvement to the glass and how it greatly improved the overall curb appeal of the property. Moving forward, Valcourt is developing a window cleaning service program to help mitigate the reoccurrence of window stains on Park Plaza II.