I've picked up a big contract - several blocks of flats. Hundreds of windows However, all the lower windows are really badly stained from the render stuff above. I've tried Kill Rock, Vaniscale, Winsol 500 or whatever that crap is called. Nothing touches it, not even bronze wool.
Any ideas? It needs to be something that can be sprayed on, it has to be quick. It looks just like hard water droplets staining the glass maybe it's even etched it. Only it can't be hard water.