First itme trying this product....great results I think. A patio door badley stained from an over flow that had been dripping and splashing onto it for some months. Before After Of course the glass is now so shiney, the image is spoiled by the reflection of the garden fence It took a bit of doing. First attempt, I applied the RubOut in circular motion and left it for a few minutes...I then rinsed and at first, it looked much better but as soon as I ran my squeegee over the glass, I could see it had done nothing. So, I applied again, left a few minutes and then got to work with my 6" scraper(sharp side), I kept rubbing the solutiion in with a damp cloth after scraping the area. I rinsed and after running my squeegee through again, I could see the test area was lovely and clear. So I got to work proper and spent about 30-40 minutes on the entire arear(the water staining ran to about half way up the patio door). I rinsed and was pleased to see I'd done a great job. Just to be clear, I had previously tried scraping with just soapy water, it didn't touch it. Fully recommend this product. Mart.