Hi. Have recently had some plastering done around UPVC window frame. When I came to clean the frame, I took a sharp chisel and began to scrape off what I thought was excess plaster and old paint. The first section flicked off easily but further along it got more difficult and I realised I was removing a tiny ridge of UPVC (2mm wide x 1mm deep). The frame is now uneven with some of it smooth and some where I can't fully get rid of the ridge. I was wondering if there are any good products that will effectively dissolve the ridge and polish it smooth. Thanks