[gtobird]

My 68 Firebird has the original tinted power window bird glass. They have scratches and some tiny pits that look like they are from welding. I've polished glass before and understand the limitations and issues with the glass getting wavy if you polish just the damaged area.

I haven't yet tried to fill the defects, but it seems to me there should be something out there that you can fill these scratches with so you don't have to cut so deep into the glass when polishing. Since smaller windshield defects can be filled with resin, I'm wondering if any of those fillers would work.

There are a number of glass glues out there that aren't fillers and appear to be anerobic compounds which cure in the absence of air (like super glue). Since the windows are out of the car, I could lay them flat, fill the scratches with that glue and then possibly lay something like plastic wrap on them to get it to cure. After that, polish them flush.

Short of filling in the defects or replacing the glass, I do have some of the expensive glass sanding discs that are meant to grind the larger surface before polishing. I'd only go that route if no other options are possible.

This will probably be a science experiment as I'll try it on some junk glass first. I'm open for suggestions.

[Formulabruce]

I have used the resin from a yellow rain X kit and swiped it fast with a squeegee, plastic, not rubber. Easier if laying down, but still can be done

[gtobird]

Originally Posted by Formulabruce

I have used the resin from a yellow rain X kit and swiped it fast with a squeegee, plastic, not rubber. Easier if laying down, but still can be done

Interesting to find out that this has already been tried. I have a few questions

1.) Sounds like your glass was still in the car. Is that why you swiped it fast?

2.) Did you have to do anything afterwords like grinding or polishing the resin down? If so, what did you use for that?

3.) Was the repair much better looking that the scratch?

4.) Did the repair last without yellowing?

I appreciate your help and I'm sure others will find this interesting too as the scratched glass topic seems to come up every now and then.

Old Joe

[Sirrotica]

FWIW, the resin used to fill a glass imperfection from glass shops, is cured with a black light, not air, or anerobic curing. That resin is warranted to never yellow. They do buff it after it cures, to help with transparency.

You might ask someone familiar with the procedure if they have ever used it on other types of automotive glass repairs.

Dirt that gets into a crack from being driven after the injury occurs is what makes a star break visible. The guy I knew that repaired them said it was crucial to have the repair done ASAP after the injury to stop dirt from lodging in the break, leading to the repair not being clear after filling the void.

[Formulabruce]

I cured with bright sunlight, which has the whole light spectrum and light we cant see ( per directions)
I did swipe fast to avoid a run out. Looked good last year after 3 years .

[Sirrotica]

Originally Posted by Formulabruce

I cured with bright sunlight, which has the whole light spectrum and light we cant see ( per directions)
I did swipe fast to avoid a run out. Looked good last year after 3 years .

The guy I knew always had the car inside, or he had a magnetic sun shade to keep sunlight off of the repair if he couldn't get the car under a roof, such as a semi. So yes, sunlight also will harden the resin. He would work the resin a bit to make the repair as inconspicuous as possible, before he put the black light on it. As with anything, there are tricks of the trade to get the best end result.

[tjs72lemans]

I had a small pit from a gravel rock last fall. The auto glass guy put his resin in and black light on. After a few minutes he used a razor blade to scape flat. Done. Turned out ok. I would imagine a side glass would get the same treatment. Not sure polishing would get flat to rest of glass.

[gtobird]

Thought I'd update this post since I started my glass experiment. I have not yet tried filling in the scratches and pits, but I did spend the better part of a day practicing removing some relatively deep scratches on a piece of tempered glass that is similar to the characteristics of side glass in a car.

As mentioned earlier, a while back I purchased some discs to remove scratches. These are the 3" trizact discs made by 3m. They come in 5 grades and from what I can tell, you really do need to step through all 5 grades if the scratch is deep as it was in this case. Here is a link to a description of those discs from DK Hardware where I purchased them:

https://dkstatic.blob.core.windows.n.../crl03_275.pdf

In this particular case, I opted to buy the 4 grades of trizact discs and thought I would use the Cerium Oxide powder I bought at a swap meet for the final polish as I have used it in the past to do very light polishing on glass. In other words, I did not use the cerium oxide disc sold by DK.

In looking for a video of how to do this, I watched the following youtube video several times. Note, these are slightly different products, but similar in how they work.

https://www.youtube.com/watch?v=doYlaQlCloQ


I took 3 attempts at trying to get the scratch out. Here is what I found out

1st Attempt: I started with the second lightest disc and a battery powered drill. It looked like little had changed after about 20 minutes. End of attempt

2nd Attempt - now using a 3000 rpm corded drill: I spent about 2 hours on it and used all 4 grades of the discs I had, but did not bother with the cerium oxide. I could see that the scratch was about 65% gone, but could tell I should have ground on the glass longer with the most coarse disc before proceeding with the others

3rd Attempt: I'm still working on the same scratch with a corded drill, so I spent roughly another hour going through all the grades of discs again. I then polished with cerium oxide using an inch thick stiff foam polishing pad for about 10 minutes. Note: I switched back to the lower rpm battery powered drill for the final cerium oxide polish. Ahhaaaaaa, now I'm getting it. The final result was that the scratch was about 95% gone. It was about 3" long to start with and the only part that was left was about 1/4" long and you could only find it if you were looking for it and knew where it was. The rest of the area that I polished still has a very light haze through it, but you can see through it pretty clearly and appears to be no distortion as I worked glass in progressively larger patterns as demonstrated in the video.

One thing I am going to change is the cerium oxide polishing. I am going to buy some of the correct discs for it as I think it will be better. For the immediate future, I'm going to keep practicing. As others have mentioned, this takes a lot of time. I can see blowing several days and a bit of cash on discs, just getting the technique down before trying it on my car glass.

I also still intend to try the pit resin and see what results that brings.

Regards,
Old Joe

[Sirrotica]

The problem with polishing out a scratch is it usually makes the vision through the glass distorted. That may not be a problem in a side window, but it is in a windshield. I had the windshield replaced in my Wife's Pontiac Vibe, and as soon as she sat in the car, she started complaining that the windshield near the bottom was distorted. I'm just under 6 feet, and I never noticed it, she on the other hand, is 5' 2".

I ended up taking the car back and the shop owner agreed that the bottom of the windshield was distorted, ordered another piece of glass, and replaced it at no cost. He explained that being so low that the supplier probably polished a scratch in an effort to save the new glass. I felt bad that he had to redo it for free, but he told me that the supplier made it right with him, so he wasn't at all upset about having to do 2 installs.

All the polished glass I've seen done, does usually leave a visual distortion where it's done. If you're fine with it in a non critical area, then it's of no problem.

[gtobird]

Originally Posted by Sirrotica

The problem with polishing out a scratch is it usually makes the vision through the glass distorted. That may not be a problem in a side window, but it is in a windshield. I had the windshield replaced in my Wife's Pontiac Vibe, and as soon as she sat in the car, she started complaining that the windshield near the bottom was distorted. I'm just under 6 feet, and I never noticed it, she on the other hand, is 5' 2".

I ended up taking the car back and the shop owner agreed that the bottom of the windshield was distorted, ordered another piece of glass, and replaced it at no cost. He explained that being so low that the supplier probably polished a scratch in an effort to save the new glass. I felt bad that he had to redo it for free, but he told me that the supplier made it right with him, so he wasn't at all upset about having to do 2 installs.

All the polished glass I've seen done, does usually leave a visual distortion where it's done. If you're fine with it in a non critical area, then it's of no problem.

I have no doubt that it's easy to distort glass. The problem is when you hire someone to do it, they concentrate on getting the scratch out and focus on the smaller area with the scratch. Doing it properly means progressively spreading out the work area farther and farther as you go to gradually blend it in. I can only imagine the amount of time and skill it would take to make it look good on a windshield. Add in the curvature of the glass and the fact that it's not as hard as side window glass and you are likely to get waves in it. Moreover, making it viable means that the work has to cost a lot less than a new windshield to make it attractive to a customer. I don't see how you do that easily when it takes so long to do this.

From the experiement I did, to get a 3" scratch to blend, I had to do a surface area on the scrap glass that was almost as big as an entire rear quarter window, hence the hours of work and still needing more work to do the final polish.