I'd never used a clay bar before, in fact, I had no idea what it was until I started looking at ways to look after my car (the irony). I used one last time I washed my car. I read up as best I could on how to properly use one, watched numerous YouTube videos etc to ensure I didn't do more harm than good (everyone said to "Use loads of lubricant to avoid marring!!" - I didn't fully understand what marring was but I did know that I didn't want it!). Fortunately I didn't have the time to do the whole car so the only areas I did were the front and rear windows (in the hope to remove the film of dirt that normal washing doesn't shift). Anyway... I thought all was well until two things: 1. I drove into the sun a few days later and noticed my windscreen was riddled with spiderweb-like scratches. Oops! 2. I was filled up at the petrol station and noticed what I thought was a hair on my rear window (factory tinted) - turns out it's a scratch that goes through the tint. Gutted! There's a couple of them. Needless to say, it's completely put me off using a clay bar anytime soon. I'm sure they probably are brilliant in the right hands, but I'd rather roll my bar up into a ball and chuck it at a pigeon. I assume the rear window is beyond help. Is there something I can use on the windscreen to remove the scratches? I think I've got some Autoglym Car Glass polish knocking about but don't know if this would be the right product to use? I still don't know how it happened. I did the usual washing ritual beforehand... snow foamed the car before giving it the two-bucket with a lambswool mitt. So it's not as if it was filthy and covered in grit when I started! I kept the piece of clay warm in my hands, used plenty of lubricant on the clay and the glass, didn't apply too much pressure, kept kneeding it / turning it over. What went wrong?! Any pointers on properly using a claybar would be very helpful, I MIGHT give it one last chance before sculpting something rude out of it and chucking it in the bin, or it might at least be nice to see where I went wrong. If it makes any difference, I purchased Auto Finesse Clay and Meguiar's Quik Detailer. Cheers!