Scratched windows?

[89RedDarkGrey]

 

[C Carl]

Thank you for posting this. Time and muscle are needed to clean up a large scratched area of glass , as acknowledged in the presentation. However : 60 years ago when I was a kid doing optical fabrication , it was well known that the very fastest glass polishing agent was , and still is , Cerium Oxide. (For plastic , Titanium Dioxide , or Lead Trioxide). At that far ago time , it was still conjecture as to whether a Beilby Layer formed in glass polishing , as had been recognized in metal polishing. I believe it is now accepted that it does occur in glass polishing too. So , just as some abrasives work better than others in metal polishing , the Cerium Oxide should still be more effective than anything else. Look up GT Glass Technology Products. They DO use Cerium Oxide , and have a number of different polishing laps. As they must remain a commercially viable company , I doubt any other compounds or laps could do as well. In any case , I expect anyone "doing it yourself" will get a nice workout taking scratches out of your windshield. If you are as beat up , arthritic , and bone on bone as I am , work the kids and grandkids ! Good luck , and perhaps race one technique against the other and report back !   I'll place my bet on the tried and true. Cerium Oxide. Beilby Layer.  Too pooped to polish ,  - Carl

[Curti]

Yes, I concur with C Carl.  I have polished many scratches in rare headlight lenses. There are polishing kits that can be bought on-line.  The one I have is used with a variable speed electric or air tool.   You start out with the finest grit so it takes some time.

[Bhigdog]

After watching the video I have to disagree with a couple of things the video recommends. The most glaring fault is concentrating on only the scratched area. This will distort the view through that area. The entire glass should be polished evenly  to prevent this. He also appears to be using a rotating buff. This is inviting heat build up and swirl marks.

I'm guessing there is more than one way to skin this cat. Below is a post I created in 2010. The system worked very well and cost me a total of $5. It is, however, time consuming. I spent about 3 hours removing the wiper scratches in my windshield. OTOH, I saved about $750 or was paying myself $250 an hour......Bob

 

If the scratches will "catch" your finger nail the glass is toast. If your finger nail will slide over the wiper  marks they are, with patience, repairable. Below is a post I submitted in 2010 detailing how I successfully removed wiper marks from my 56 Chrysler wind shield. I will add that this will not remove the micro pits that every windshield picks up over time but will restore your glass to quite usable condition...................Bob

 

In the interest of sharing knowledge............

I'm finally getting around to installing the glass in the 56 Chrysler. I've been fretting about the windshield and the wiper marks in it for two years now. The "marks" were not quite deep enough to actually "catch" a finger nail but they definately could be felt. Imported repro glass is available for about $650 without a date code. I'd heard both pro's and cons about polishing out the scratches. I'd heard that it can't be done,  that it would cause distortion because it would leave a shallow hollow where the groove was or heat build up would crack the glass.

Being both a frugal type and having nothing to lose I figured I'd give it a try.

First I needed a polishing "kit". I looked at ready made kits and saw they were nothing more than a hard felt pad and some cerium oxide polishing compound.

So instead of p**sing away $75 bucks on a kit, I cut down an old backing disc from my DA sander to 3 1/2" diameter and epoxied a 3/8" thick pad of hard felt on the bottom. My local glass shop sold me a baby food jar of cerium oxide for $5. So now I had my kit.

The kit sellers say to chuck their pad in a drill to polish out the scratches. I figured that was the cause of the distortion problem. Folks were using the pad like a disc sander and concentrating on the scratches. To get around that I mounted my pad on my DA sander and used it only on the orbital mode. Also, instead of concentrating on the scratches I evenly buffed the glass and only gave the scratches a bit of extra buff time.

I'd also heard that the glass could crack from heat build up. Not true. I mixed the cerium oxide with water to make a loose paste. Wet the pad, spread a bit of paste, and started buffing VERY slowly and lightly. As long as everything is wet there in no heat build up. I kept a spritz bottle of water close by and just kept spritzing, buffing, pasting, spritzing buffing and checking.

In about an hour all traces of the scratches were gone, there was no distortion, and I'd saved almost enough to pay for the new tires for the 56 that I need to order. The whole project took an entire morning to do.

If you decide to try this here's few hints. The hard felt is available from McMaster-Carr by the square foot. Or, I have have enough left over to cut a disc for someone or two or three. Keep the glass wet and keep the orbital speed about mid way. Draw a line  under the scratches, with a magic marker, on the back side of the glass. That way you can find them and you only have to wipe a small area clean to check your progress. Do not let the pad get dry. It will pack dryed oxide into the micro pits that are in every used windshield and you will spend an hour with soapy water and a tooth brush getting it out. Do not ask how I know this last bit...............Bob

Edited April 18, 2010 by Bhigdog (see edit history)

[Bud Tierney]

I dimly remember people talking about "jewelers rouge" for de-scratching glass, including windshields, if not too badly worn...

Does anyone know if the "jewelers rouge" is the cerium oxide described above??

I've also used common toothpaste (and elbow grease, it's slow) to clean up/polish  minor glassware  clouding and minor scratches, but never tried it on a windshield......

[C Carl]

Jewlers rouge is far slower than Cerium Oxide. It is used to polish extremely precise optical surfaces to tolerances finer than what can be obtained with Cerium Oxide. These tolerances are TOTALLY insignificant in windshield applications. Bob's description of the technique is superb. Every detail is dead on accurate right down to the futility of trying to polish out pits. As fast as Cerium Oxide is in polishing glass , the depth of the pits would take a monstrous amount of time , and the surface of the glass would then be distorted from flat. Pay particular attention to Bob's directions , and do keep the process wet.  - Carl

[PFitz]

Jeweler's Rouge is made from a form of iron oxide.

 

https://en.wikipedia.org/wiki/Iron(III)_oxide

 

As C.Carl points out it's very slow cutting. When I worked in a museum exhibits shop, we used jeweler's rouge to polish the edges of Plexiglas for free-standing museum display cases.  Anything more abrasive than that would over heat, smear, and burn the edges of the plexi.  

 

If you tried to polish scratches out of glass just using jeweler's rouge, it would be a contest to see which went first, the scratch,.... your arms, ... or the motor on the buffer.

 

Paul

Edited September 9, 2017 by PFitz (see edit history)

[C Carl]

Titanium Dioxide or Lead Trioxide for plastic.  - Carl

 

P.S. My source for this information came from Scientific American back in the '50s. There was speculation and experimentation in order to explore the possibility of using plastic optics for certain applications. Plastic has indeed proved useful for certain products. Plastic certainly has advanced in the 60 years since the article I read. It is conceivable that some other abrasives might have evolved along with plastic. You can be sure , however , that a great deal of research had been done by the S.A. author(s).  - CC

 

Edited September 9, 2017 by C Carl
Add P.S. (see edit history)