# Machine Sanding Glass - Do NOT do this!



## Mike Phillips (Jan 26, 2007)

*Machine Sanding Glass - Do NOT do this! 
*

*Machine sanding glass*










*Unless* you have a very high confidence level in your skills, physical ability AND are tenacious enough to finish what you start.

Wiper scratches and swirls in glass

This is a restored 1957 Chevrolet Corvette. Over the years wiper scratches have built-up on the windshield.
































































*Here's the driver's side...*



















The least aggressive process

I started out machine polishing using CarPro Ceriglass Polish with a CarPro 5" Rayon Pad on a FLEX cordless rotary polisher.










And "yes" this definitely improved the clarity of the glass. I also did this LIVE for a Mobile Tech Expo educational class on Thursday, April 22nd, 2021. You can watch that video *here*.

After working really hard at using only the rotary polisher I finally came to the conclusion that the swirls, wiper marks and scratches were too deep and wide-spread to continue down this path. So after trying the least aggressive process and then moved on to machine sanding.

*Machine sanding glass with a Porter Cable...*





































The sanding process took hours using multiple grits of sanding discs including Mirka Abralon #1000 through #4000 followed by 3M Trizact #3000 and #5000.





































*Vindicated*

For years I've been sharing how to polish scratches out of glass and one thing I always tell people is it's VERY MESSY. Look at the plastic drop cloth - it's covered in glass polish splatter.





































Look at all the splatter on the drop cloth covering and protecting the paint.



















And "yes" it's on the plastic drop cloth covering the interior and also on the Autogeek Cover-up Towels.










I've been down this road enough to know to also cover the 1972 Cutlass we're using for a wetsanding video class.










So if you EVER machine polish glass - remember to cover and protect everything or you'll be hating yourself later when you have to clean-up.


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## Mike Phillips (Jan 26, 2007)

Continued...

After I arrived to the point where I was done with the sanding, I started in on the machine polishing to remove the sanding marks. This is *MORE DIFFICULT* than the sanding step. With the sanding step I pressed down about 5 pounds on the polisher, maybe a tick more. For the rotary step I pressed down at least 10 pounds, maybe more and did this for HOURS.

And it's just as mess as the sanding step. Maybe more messing since the pad slings splatter out easily due to single centrifugal action of a rotary polisher.










Here's everything I could find after the job for this scary picture.










This is a 3M Trizact #5000 sanding disc. What you see is a build-up of SLURRY on the face of the sanding disc. Slurry is the water and glass particles that are sanded off the windshield.










When I carefully remove the plastic drop cloth, you can see the paint is for the most part still in pristine condition. My February 3-day detailing class detailed this car and use IGL Poly to ceramic coat the paint.










*The inside of the windshield also had a film on it. Here's some education. *

Sometimes you can remove a FILM using a liquid, as in a liquid glass cleaner. Sometimes you need to use a glass-safe polish. And that's what I did.










*Topical versus Sub-Surface Glass Polishing*

The BLACKFIRE Water Spot Remover is for cleaning and removing TOPICAL stains off the surface of glass. It is NOT for removing scratches IN the glass. For my purpose, it worked perfect. If you have scratches, wiper marks or swirls IN glass you need a glass polish that contains Cerium Oxide. Remember that. So many experts on YouTube and Facebook always telling me, _any old polish will work_. What they have done is shared with me their "knowledge level".



















This is real simple folks... use a microfiber applicator pad and then contort yourself to get the job done.




































































































BOOM!

_*Crystal Clear Glass!*_










*And most important - crystal clear glass for the DRIVER.*










Now to finish the job. I use the PBL Surface Coating, my favorite glass coating for both the inside and the outside. Sorry no pictures of me applying it to the outside as no one was around when I did the work.





































_Here's the final results..._





































_Ready for another 64 years of driving fun!_

2021 - 1957 = 64










Here's what I used

*NOTE:* The below is just to show you what it takes, I HIGHLY DO NOT RECOMMEND ANYONE SAND GLASS. It's a can of works you do not want to open.

*Tools*

FLEX PE-150 Cordless Rotary Polisher

Any rotary or any orbital, both free spinning and gear-driven will work for machine polishing glass. The biggest difference is in correction speed and rotary trumps orbitals.

Porter Cable 7424XP Dual Action Polisher

5" Dual-Action Hook & Loop Flexible Backing Plate

*For Sub-Surface Glass Polishing*

CarPro Ceriglass Glass Polish 500 ml.

5" Polishing pads and interface pads

CarPro Rayon Glass Polishing Pad - 5 Inch 2 Pack

Griots Garage BOSS 5.5 inch Innerflex Pad - I recommend getting a few of these as they will wear-out due to overheating.

*Sanding Discs*
Autogeek no longer carries the #5000 discs, I just have some laying around gathering dust.

6 Inch MIRKA Abralon Sanding Discs

3M Trizact Hookit 6 Inch Foam Discs P3000 - 02085


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## Mike Phillips (Jan 26, 2007)

One comment...

People say,

_That's too much work! That takes too much time!_
_
_
_Just break the glass and have it replaced!_

*Duh. 
*

That's fine with a new car but when it comes to Special Interest Vehicles, sometimes you cannot get replacement glass. More common though is - removing the windshield will uncover other problems, like rust or really bad rust --> cancer.

So what starts out as a SIMPLE windshield replacement turns into a full restoreation as you chase the rust around the window frame throughout the rest of the car. That's fine for some people, but not for everyone. Some people don't want to take their car off the road for years. They want to DRIVE it tomorrow.

That describes the owner of this 1957 Corvette. He doesn't want to take the car apart - BUT he wants to be able to safely see out of the windshield at night or without being blinded by glare.

So for everyone that want's to make the comment like I shared above, I get it - but there's a time and place for everything and everyone can choose for themselves the best approach for their car detailing project.

Make sense?


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## Mike Phillips (Jan 26, 2007)

And here's the link to a VERY THOROUGH VIDEO that covers machine glass polishing.

It does not cover machine sanding glass. But it is very in-depth.


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## Rappy (Oct 2, 2020)

Fantastic write up Mike :thumb::thumb:

I really admire the amount of effort & work you put into your posts.

Thank you.


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## muzzer (Feb 13, 2011)

Nice, always good to see your posts Mike and i like the concept of sanding the windscreen but i'll be damned if i am going to attempt it after reading your write up :lol:

Great work though fella as always :thumb:


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## ridders66 (May 24, 2019)

What a fantastic write up Mike. Every credit for having the knowledge and the time to spend so much time on a windscreen. Looks superb mate.


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## Andyblue (Jun 20, 2017)

Great write up and that is one lovely motor :thumb:


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## chongo (Jun 7, 2014)

That was a fantastic post mike :thumb::thumb:


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