I was looking into this concept again earlier this summer when I pulled all of the frames off of my side glass and began to clean all of them up, I was rather shocked to see how truly horrible they really were! I had already realized an issue on the inside of my back glass about a year or so ago and now have two date correct back glasses, BOTH with some rather serious scratches so I began to doubt I could ever find a set of dated windows for my Coupe that would be worth installing in the project.
ALL 7 windows NEW, and adding the dates to them seem to be absurd, I know I have no choice on the windshield but my budget would never allow for ALL NEW GLASS on the whole car.
FIRST: I tried finding a glass shop to do polishing. No luck. I tried local car restoration shops and the Internet for somebody in the 100 mile radius to take them to and nobody even returned calls or emails. Then, like others, I tried the $80 Eastwood Deep Scratch Kit and using a drill motor, results were essentially a swing and a miss. 2nd, I tried the same Eastwood kit on a buffer/polisher and had a friend who does granite/monument work and his guy gave the same window I had worked on about an hour, then gave it back saying he's not interesting in doing more. It had signs of improvement but the outlook for doing all of the glass was very grim at best.
Once again, I went to the Internet and found a guy named Pedro in Florida doing a YouTube video and it looked like not only him, but there were companies and individuals everywhere doing glass polishing successfully with similar discs like the ones found in the Eastwood kit and/or cerium oxide (powder or solution)... on buildings at least, and the results looked rather amazing, not causing distortion in the final product either. Yet, when I tried calling anyone, even Pedro of Florida, no return calls or emails when I stated I wanted to do Classic Car Glass.
I believed now that the real issue was Liability. Nobody wanted to take a chance on my "Classic Car. Date-Correct Glass".
Eventually, one guy somewhat local to me, DID call me back at least. He said he ONLY did architectural work (on buildings) and was only insured for the same but was having extremely good success using the GlassRenu System on those jobs.
I had already looked into GlassRenu Systems, I had even given them a call and asked for recommendations for local companies (this is where I got the name of the guy who ended up calling me back from).
So, I tried rolling the dice again. This time, I bought GlassRenu's "Professional Grade Scratch Removal System" (cost $250 +shipping).
BINGO! Now, it was recommended to use a variable-speed buffer in the many YouTube Videos on GlassRenu that I had watched and the variable buffer most often recommended was a Mikita variable-speed. I liked and trusted this choice since they offered the "numbers" on the wheel to help you to get to the correct RPM's for maximum success. Having bought that too, I am over $500 into this mess...So much for saving money, right?
The difference now is that I am successfully removing EVERY deep gouge and every single scratch and I am actually succeeding in removing sand-damage too! (My car was in the desert area all of it's driven life).
If you want to spend the money on new glass, that may be the "easy button" but since I was also hoping to retain all of the original glass without ALSO having the added cost/time to add in the etchings onto new glass, I feel it was the best choice to just buy this kit.
Be sure to set aside a weekend or three. You can put between 1 to 3 hours each window. (Actually less on some that have minimal issues). I think the time spent depends on how brave you are in process. You kinda learn as you go along what works best on what kind of damage so the learning curve may vary.
My glass at this time is progressing very well. The BLACK DISCS sent in the kit really do a lot of major work getting the glass readied for polishing, they are probably the most effective part of the process in the scratch removal process. Now, I have found some very deep pits from rock/gravel impacts that would take more time to remove but I have removed some VERY DEEP GOUGES, all minor sand-damage pitting and even DA sander damage (looked like 80-grit Da sander kissed a window at one time) and ALL of that came out 100% perfect in my opinion...NO DISTORTION I can detect at all.
The "Grey Discs" are the most "consumable" item in the kit. I have since bought a 2nd 10-pack. My glass was in some cases as bad on the insides as it was on the outsides and I did not wish to use the black disks much at first, for fear of them being to aggressive but in hind-sight...I could have saved time and money had I chose to just do the whole window areas with extreme damage, using the black discs FIRST.
You should like the results. I really struggle to notice any issues at all with the glass now and everything I find wrong, a bit more time seems to ALWAYS remedy the problem...As I said, my glass was BAD NEWS, REALLY BAD NEWS to begin with!
The hardest choice I made was whether or not to buff through a Carlite Logo on the wing vents since the sand damage was on the logo-side of the glass on them. One side vent, I buffed through the damage including the logo etching and the other side, I did not (yet) buff through the logo but you can still make out the sand-damage. You will likely have similar choices
If you are thinking about this, do a search on YouTube for "GlassRenu" and watch some of the videos.