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by chiph
765 days ago
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UV exposure can certainly cause this, but what about their train washing systems? They commonly have large rotating plastic brushes and if grit gets caught up in the brush it's going to sand anything with a lower Mohs hardness. Los Angeles Metro wash system - note that they use glass and don't have this problem. https://www.youtube.com/watch?v=k1JxVOzAz6E |
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