Machine Sanding Glass - Do NOT do this!

Mike Phillips · 05-19-2021, 03:00 PM

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.

Mike Phillips · 05-19-2021, 03:01 PM

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

For Topical Glass Polishing

BLACKFIRE Glass Water Spot Remover 32 oz

Pads?
Any foam or fiber cutting pad works for topical glass polishing. The thing to keep in mind is once you use a pad with a dedicated glass polish you should consider this pad dedicated for only working with a dedicated glass polish. Do not wash with paint polishing pads and do not use to polish paint.

Glass Coating

Pinnacle Black Label Diamond Surface Coating

Microfiber Towels

The Rag Company FTW Premium Orange Microfiber Towel

**PaulMys** · 05-19-2021, 05:58 PM

That is just incredible, Mike.

On top of the tedious process needed, and the amount of skill, I would imagine that the materials used would cost a small mint as well.....

**Bruno Soares** · 05-19-2021, 06:26 PM

Pretty wild. I guess only viable on a classic car that you can’t easily source new glass for. Any modern vehicle would probably be cheaper to replace the glass than paying your labor to do this much work.

Mike Phillips · 05-19-2021, 06:41 PM

It was kind of a Rabbit Hole journey.

Once I started, I was challenged to complete the process, not only to fix the glass but to go through the process and thus be able to speak about the topic from first-hand experience but to hopefully either help or prevent others if they’re in this situation.

I’m glad I did it and I’m glad it’s over.

**Sizzle Chest** · 05-19-2021, 07:19 PM

Holy cow, Well done, you must be smoked after that!!!

**Prange** · 05-19-2021, 07:25 PM

Mike, you are the Grand High Exalted Mystic Ruler.

**2black1s** · 05-19-2021, 11:19 PM

I'll pass. I guess there are some instances where a process like this is necessary but I hope I never find one.

Mike Phillips · 05-20-2021, 07:02 AM

Originally Posted by 2black1s

I'll pass.

I guess there are some instances where a process like this is necessary but I hope I never find one.

Here's another instance. Owner buys a brand new Audi R10, buddy accidentally puts a small scratch in back window with watch band. Owner doesn't want to replace glass, asks me if I can fix it.

Tedious work.

It's a skill set that comes in handy but most people should never attempt it.

**Skier404** · 05-20-2021, 08:01 AM

Turned out great Mike! You got some hours poured into the glass work on that little Vette!!

A skill set often not needed. With some classic cars where there is no glass replacement options available, it is a valuable skill to have when you need it.