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| Shane Hong adjusts the gas jets to melt away
scratchiti from a subway car windowpane. | An example of scratchiti |
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| Shane Hong adjusts the gas jets to melt away
scratchiti from a subway car windowpane. | An example of scratchiti |
Graffiti has long irked New York City subway riders but recent advancements in treating the surfaces of subway cars have lessened the problem significantly. To compensate for the loss of surfaces to paint, vandals moved their defacing skills to subway car windows, creating deep scratchings in the glass, called scratchiti, which first began to appear in the mid-1990's.
In 1997, the Metropolitan Transportation Authority replaced 62,000 pieces of damaged glass at a total cost of $2.6 million. Estimates for replacing all scratchiti-defaced windows reach as high as $70 million annually. So far, there has been no cost-effective method to remove the scratches. Some processes have been tried-repairing the glass by polishing it or patching it with optical grade epoxy-but the results were unsatisfactory, since the quality of the repair was unacceptable and the cost prohibitive.
Coming to the rescue is Prof. Shane Hong, professor of mechanical engineering, who has created a "scratchiti buster," a device that applies a flame to the window's surface, melting the glass to erase scratches and repolish the surface. Prof. Hong has created a prototype that includes a small propane torch to be controlled by a mechanized arm that would attach to a subway car window. The operator could then re-locate the arm from one window to another.
Dr. Hong's scratchiti-buster directs intensive heat near the scratch marks, melting a thin layer into liquid, which changes the glass's viscosity. As the glass cools down, the surface tension evens out the indentations made by the scratchings. Once cooled, the glass is as smooth and even as it was originally, without grinding or polishing. His work is being supported by a research grant from the National Research Council and a grant from the National Science Foundation and is being developed in his Environmentally Conscious Manufacturing Laboratory for Industrial Quality and Productivity. Dr. Hong's other areas of research specialties include economical cryogenic machining and micro-robot development for dental root canal treatment.