A commercial property owner reported damage to more than 30 windows on the 15th and 16th floors of a high-rise building. There was a question as to whether or not a specific glass cleaner and cleaning method of the janitorial service caused the scratches to the windows.
U.S. Forensic was asked to determine if the windows were indeed damaged. If so, what was the cause of the damage? We were also asked to provide a method and cost to repair the damage.
Our work to complete this assignment was performed under the direction of Asher Cohen, P.E. Our evaluation of the building consisted of obtaining a history related to the installation, sealing, and cleaning methods of the windows in question. In addition, Mr. Cohen visited the site to inspect the 17 story commercial office building. The depth, length, and orientation of the scratches were measured and patterns were noted. Under magnification, we observed particles on the glass surface, and we noted several instances where scratches originated from a particle. We observed what appeared to be pitting on the glass surface and micro-cracking along several of the cracks. During the manufacturing process of tempered glass windows, glass particles and other airborne debris can fuse to the glass surfaces during the heating and quenching process if the glass was not properly washed prior to entering the furnace. The particles and debris fused to the surfaces of tempered glass can often be indistinguishable without close inspection or the aid of optical microscopy. As a result, tempered glass contaminated with surface particles and debris can be delivered to the site, installed, and reside in place without detection until the glass is cleaned. During the cleaning process, the use of plastic or metal scrapers or other hardened objects used to remove various types of construction debris can dislodge the fused particles as they are passed along the glass surface, resulting in the formation of pits and scratches on the glass surface. The damage was not due to cleaning solutions, methods, or equipment of the janitorial services after installation, but instead to the manufacturing process of the tempered glass.
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