Today while cleaning my car I discovered a stain like substance that I can't remove while washing my car with car shampoo, then I tried using Fine Glass window and glass cleaner but the stain doesn't seem to disappear, parang nagharden na siya and dikit talaga sa glass? How do I remove this? I suspect na either waste ng ibon yan or waste ng tao(Yes, kasi nakapark yung car ko sa parking ng condo and above ng car is isang tubo na galing sa condo ng ibang tao baka tumulo) :| help!