Questions About Polishing Glass to Remove Scratches

[FrankS]

I have a possible project coming up where the exterior glass will need to be polished to remove scratches.

It's a 1969 Z28 Camaro with the original glass.



I've seen it done and read some articles but have never done it myself.

I have some questions:​

1. Which is better to use, a rotary or a DA?

2. What speed should be used for the rotary or DA? I'm thinking 1500 rpm for the rotary and full speed for the DA?

3. I know some have taken about 2 hours just for the windshield, not including the prep work. If the windshield was divided into four sections, that's about 30 minutes per section, that's a lot of passes in just one section. How do you know when is enough? Do you do a few passes and then wipe and check and if needed repeat the process?

4. Do you use the same procedure with the side and back windows?

5. It looks like this is the polish to use: CarPro Ceriglass Glass Polish, windshield polish, water spot remover

6. Should I go with the 5" or 3" pads? I'd rather use the 5" pads to knock it out quicker: CarPro Rayon Glass Polishing Pad, glass leveling discs

7. Any other suggestions? I know about covering up so as not to get splatter everywhere.

 

[Setec Astronomy]

Boy that's going to be real glass, not whatever that soft stuff is they use today (especially Asian cars). I always use a rotary, and the pad size is going to depend on the curvature of the windshield because the glass pads don't have much give. That windshield looks pretty flat so you should be ok with the 5", unless you want to edge it with the 3".

And yes a lot of passes and a lot of checking and a lot of water to keep the glass from getting hot (which it will). The reason it takes so long is that it's really pretty mild (for glass)--it's kind of like trying to take out deep marring on paint with a finishing polish. There is a sanding method out there using some 3M PSA discs that I'd like to try some day.

Oh, and don't put too much stock in my opinions, I've only polished windshields a few times.

 

[FrankS]

Boy that's going to be real glass, not whatever that soft stuff is they use today (especially Asian cars). I always use a rotary, and the pad size is going to depend on the curvature of the windshield because the glass pads don't have much give. That windshield looks pretty flat so you should be ok with the 5", unless you want to edge it with the 3".

And yes a lot of passes and a lot of checking and a lot of water to keep the glass from getting hot (which it will). The reason it takes so long is that it's really pretty mild (for glass)--it's kind of like trying to take out deep marring on paint with a finishing polish. There is a sanding method out there using some 3M PSA discs that I'd like to try some day.

Oh, and don't put too much stock in my opinions, I've only polished windshields a few times.

Thanks Setec! I think I'll get the 5" and 3" pads. I think the 3" pads would be better for the rear side windows.

 

[Setec Astronomy]

Oh, you're doing ALL the glass? That will be a lot.

 

[FrankS]

Oh, you're doing ALL the glass? That will be a lot.

Yes, he's got scratches on all the glass. I know it's going to be time consuming for sure.

He wants to keep the original glass if possible.

 

[Setec Astronomy]

He wants to keep the original glass if possible.

I would too. Nice car, good luck with it!

 

[Nick McKees37]

3. I know some have taken about 2 hours just for the windshield, not including the prep work. If the windshield was divided into four sections, that's about 30 minutes per section, that's a lot of passes in just one section. How do you know when is enough? Do you do a few passes and then wipe and check and if needed repeat the process?

Continue working the section until all the defects are removed. Glass is a very hard substrate, unlike paint which is soft (relatively speaking, of course).

Last summer a gentleman with a brand new Lincoln hired me to fix a couple scratches in his windshield that he induced himself (don't ask how). The scratches were about 10" x 10" section and it took me nearly 40 minutes to completely remove them. I used a Porter Cable 7424xp, CarPro CeriGlass and a Rayon Glass Pad (5"). I chose the Porter Cable because I knew that if I accidentally induced more scratches (pig tail with a DA versus arc scratches with a rotary) they would be easier to remove. It's not uncommon to induce scratches with a polish as abrasive as CeriGlass (cerium oxide is a very sharp, aggressive abrasive). Shake the polish often and take your time.

Yes it takes a lot of time and a lot of patience to polish an entire windshield. I hope you're charging him a pretty penny.

5. It looks like this is the polish to use: CarPro Ceriglass Glass Polish, windshield polish, water spot remover

Great choice, as CeriGlass is currently the only cerium oxide based glass polish that we carry.

6. Should I go with the 5" or 3" pads? I'd rather use the 5" pads to knock it out quicker: CarPro Rayon Glass Polishing Pad, glass leveling discs

I would use the 5 inch pad.

7. Any other suggestions? I know about covering up so as not to get splatter everywhere.

Cover the entire vehicle outside of the glass and charge him a large sum of money.

 

[Marc Hufnagel]

I had a place polish out a streak made when a bit of concrete got caught under my wiper. Car was brand new and actually happened before I bought it. 3 hours but completely disappeared. Dealer paid for it. 135.00 It was an Infiniti.

 

[Setec Astronomy]

I used a Porter Cable 7424xp, CarPro CeriGlass and a Rayon Glass Pad (5"). I chose the Porter Cable because I knew that if I accidentally induced more scratches (pig tail with a DA versus arc scratches with a rotary) they would be easier to remove. It's not uncommon to induce scratches with a polish as abrasive as CeriGlass (cerium oxide is a very sharp, aggressive abrasive). Shake the polish often and take your time.

Nick, I've been using the old Diamondite Glass Resurfacing Crème...was that a cerium oxide polish and how would you rate its aggressiveness vs. CeriGlass? I never had any polish-induced marring from it that I could tell, even when I used to use the hard-as-a-rock LC glass pads.

 

[Nick McKees37]

Nick, I've been using the old Diamondite Glass Resurfacing Crème...was that a cerium oxide polish and how would you rate its aggressiveness vs. CeriGlass? I never had any polish-induced marring from it that I could tell, even when I used to use the hard-as-a-rock LC glass pads.

Aggressiveness is comparable. Where it differs is the quality of the abrasives. Glass Resurfacing Creme contains smaller, more refined cerium oxide abrasives, albeit a far more concentrated blend compared to Ceriglass.

Hold onto your bottle of Glass Resurfacing Creme. It's highly sought after in the detailing world.

 

[Setec Astronomy]

Um...but Nick...it sounds like you're saying that the Diamondite product might be better, which begs the question of why it disappeared from the Diamondite line even before the Diamondite brand disappeared. Sounds like it might make a great McKee's 37 product--if you can still get the powder, which I'm assuming is the problem.

 

[Mike PhillipsMike Phillips is verified member.]

Thanks for taking this from PM's to the forum Frank.

Sorry for the late reply but busy with other hot projects, looks like you've recieved a lot of great info so far.

 

[Nick McKees37]

Um...but Nick...it sounds like you're saying that the Diamondite product might be better, which begs the question of why it disappeared from the Diamondite line even before the Diamondite brand disappeared. Sounds like it might make a great McKee's 37 product--if you can still get the powder, which I'm assuming is the problem.

Glass Resurfacing Creme was discontinued well over four years ago, when McKee's 37 was still an idea.

The reason we stopped offering the product is because the abrasive powder was no longer available. Nobody has anything comparable that I've found yet, so until we find a new supplier that can offer the same quality abrasive powder, it will be "on hold" indefinitely.

That's not to say CeriGlass is a bad product; Glass Resurfacing Creme was simply an outstanding product.

 

[Mike PhillipsMike Phillips is verified member.]

I have a possible project coming up where the exterior glass will need to be polished to remove scratches.

It's a 1969 Z28 Camaro with the original glass.



I've seen it done and read some articles but have never done it myself.

I have some questions:​

Let me take a stab at them...

1. Which is better to use, a rotary or a DA?

A rotary is faster since it's direct drive and single rotation but it's harder on you. If it were me, I think I would opt for the PC because either way it's still going to take time.

2. What speed should be used for the rotary or DA? I'm thinking 1500 rpm for the rotary and full speed for the DA?

The faster you run a rotary the more heat you're going to generate. This has two effects.

1. You heat up the glass. I think the glass can take the heat but I would be cautious about heating up the vinyl interlayer laminated between the two layers of glass. I don't know from experience if there could be a problem but I also wouldn't want to find out there is a problem the hard way.

2. The heat will cause the glass polish to evaporate. Drying out of the glass polish is already and issue. More heat means more evaporation.


The PC is a much safer option as it creates less heat and it's physically easier on you.

For those of you who have never used a rotary buffer to machine polish scratches out of a windshield I can tell you from experience it's cumbersome at best to hold a rotary buffer at an angle and press the buffer hard against the glass for long periods of time. The PC is much easier on the human body.


For more info on how glass used in cars is made simply do a Google search using these search terms

how is safety glass made

3. I know some have taken about 2 hours just for the windshield, not including the prep work. If the windshield was divided into four sections, that's about 30 minutes per section, that's a lot of passes in just one section. How do you know when is enough? Do you do a few passes and then wipe and check and if needed repeat the process?

Yes you simply wipe off the residue and inspect. Buff until you're happy with the level of defect removal.

Here's my article on this topic including "The Buddy System".

Glass polishing - How to remove scratches in glass

4. Do you use the same procedure with the side and back windows?

Yes.

5. It looks like this is the polish to use: CarPro Ceriglass Glass Polish, windshield polish, water spot remover

I have had good luck about 95% of the time.

My free advice and my best advice is to TEST FIRST and make sure you're not leaving scratches in the glass at the same time you're trying to remove them.

When it comes to the windshield, test on the PASSENGER SIDE not the DRIVER'S SIDE. (Don't ask me how I know)

6. Should I go with the 5" or 3" pads? I'd rather use the 5" pads to knock it out quicker: CarPro Rayon Glass Polishing Pad, glass leveling discs

I'd suggest using the 5" pads, which fit a 5.5" Lake Country Backing plate for the Porter Cable. Major on the majors, don't major on the minors. This means do big picture buffing, make the majority of the glass look new again don't get caught up on trying to remove 100% of the scratches 1/4" away from the perimeter of the glass unless the owner is willing and happy to pay for your time and materials. Show him this thread.

7. Any other suggestions? I know about covering up so as not to get splatter everywhere.

Nope. Something cold to drink and some music to listen too...

 

[Setec Astronomy]

The reason we stopped offering the product is because the abrasive powder was no longer available. Nobody has anything comparable that I've found yet, so until we find a new supplier that can offer the same quality abrasive powder, it will be "on hold" indefinitely.

Funny how those things work. In this big-business world, niche products and suppliers are fading away, it seems.

 

[axel06]

Frank wish I could help you out, mike gave his class this same method and I tried it out yes you will need a buddie to wet the polish, no question you gunna nail it...

 

[kaliagent2001]

Great question frankS, enjoyed reading these treads on how to correct glass. I recently bought McKee's 37 High Performance Glass Restorer and it worked great for what I needed it for but this CarPro Ceriglass Glass Polish I must try. I have a customer with a 53 bel Air in a week that asked me the same question regarding a scratch on his windshield. .

 

[FrankS]

Frank wish I could help you out, mike gave his class this same method and I tried it out yes you will need a buddie to wet the polish, no question you gunna nail it...

Thanks Axel!

Yep, Mike taught it in the class I took also (you were there). I saw it done but didn't do it myself. Just a little hesitant to do it in a real life situation on a '69 Camaro with the original glass.