Buildings with precast concrete facades like the Greenbrier Circle flex facility are inherently susceptible to window staining when windows are installed flush with the precast concrete façade, allowing rainwater to wash across the windows and deposit minerals from the precast onto the glass surfaces. These minerals embed themselves within the pores of the glass, causing staining that cannot be removed without more aggressive techniques. Removing these tenacious stains without creating scratches to the glass surface or causing etching (due to improper use of hot acids)
is complicated by many factors. These factors include direct sunlight, temperature of the glass surface, humidity levels, and trained workers in this craft. Every building, and often each elevation of a building, may require unique approaches to glass restoration.
After washing the windows, Valcourt performed a test demonstration for the client that removed some of the worst staining. Valcourt’s crew developed 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, whose speed was closely monitored. Workers must be trained and experienced in using this specialized procedure, because the glass surfaces can be adversely affected by the rate at which the wheel spins. Finally, Valcourt washed the windows a second time before applying a sealant to mitigate the reoccurrence of window stains on the glass.
First Potomac had initially budgeted for replacement windows, so the client was extremely pleased that for much less expense Valcourt restored the windows to the same level of optical clarity as if they were new again.