Glass Fog Light Renovation

[sleddriver]

I found an earlier post How Do I Polish My Fogs? which linked to another post DIY Fog Light Sanding Refinishing.

While I've had plenty of experience polishing both acrylic & polycarbonate, glass is MUCH harder. Tempered glass even harder still.

I'd pulled two fog lights + associated electrical items and managed to get the electrical issues sorted out: Fog Light Install and Schematic Q.

The glass lenses were badly pitted so I wanted to try polishing them before adding a protective film.

Volvo_Fog Light Lenses 001.JPG (160.21 KiB) Viewed 1906 times

Volvo_Fog Light Lenses 005.JPG (180.38 KiB) Viewed 1906 times

I started off with a RO 6" sander. This proved frustrating however because the pad isn't directly driven. However, it's what I had on hand + quite a range of assorted grit hook-n-loop paper to use with it. My goal wasn't to grind down to perfect glass, rather to remove the thousands of small tiny ones that pot-marked the surface as shown above.

After considerable trial & effort and experimentation, I had removed all the tiny ones and began the path back to clarity. However, this is where progress stalled. The glass surface was still hazy and not capable of producing a sharp light reflection. You can see the deep scratches and blurry light bulb reflection:

Volvo_Fog Light 001.JPG (362.53 KiB) Viewed 1906 times

Volvo_Fog Light 002.JPG (305.34 KiB) Viewed 1906 times

Volvo_Fog Light 003.JPG (324.04 KiB) Viewed 1906 times

At this point, I began searching for a local source of cerium oxide. I also called several glass, marble & granite businesses looking for suitable fine, hard grits. I also called several auto-glass & parts stores looking for windshield polish capable of removing wiper streaks & scratches. Result?: One glass business wanted to charge me nearly $7 for about 1/4 cup of red cerium oxide (unknown grit). I'd been led to believe there would be no charge after talking with the rep over the phone. That would have made a difference given the hassle it was to get over there before closing in the traffic and rain!

(Note: While search sites work fine (mostly) for locating products across the states, they are down-right-lousy for locating anything locally. In hindsight, much time would have been saved ordering on-line. I was surprised that even the auto parts places I called didn't have the windshield polishers seen on-line. Sign-of-the-times.....)

A fellow astronomer gave me some white cerium oxide powder with instructions to polish-by-hand. This was a dead end. Tempered glass is way too hard and the CO powder too fine for hand use. I'd run into a similar conclusion when compounding & polishing out the sled's clear coat: You get better & quicker results using the correct machine than trying to do it by hand!

One day while at the box stores looking for something else, I decided to search for something suitable. I found a "Gator Headlight Restoration Kit" containing a 3" H&L foam-pad, 800, 1500 and a 2000 grit water-proof H&L sanding discs, a foam applicator pad and polishing compound. For $14. While designed for polycarbonate lenses, I wanted to see if the finer grits would work dry on glass. Plus I could use the small H&L foam pad with the white CO powder.

It turns out the foam pad plus CO powder did the trick:

Volvo_Fog Light Lenses 006.JPG (170.95 KiB) Viewed 1906 times

Volvo_Fog Light Lenses 007.JPG (137.67 KiB) Viewed 1906 times

Volvo_Fog Light Lenses 009.JPG (152.27 KiB) Viewed 1906 times

Not perfect, but MUCH BETTER!

I'll continue refining it, then tackle the remaining pitted lens. Except this time, I'll try the drill press with a faster spindle speed to reduce time. Sometimes it's easier & more effective to hold the work rather than the tool.

Lessons Learned:

• Don't use a RO sander. You need a direct drive polisher or backing plate with a drill motor.
• Spindle speed needs to be at least 1500 rpm. 2000+ would be better with the small 3" H&L pad.
• Surface speed is very important when grinding & polishing glass. Therefore, a 4 or 6" backing plate @ >= 1500 RPM.
• You're better off shopping for suitable H&L sanding disks locally at Woodcraft or Rockler rather than the box stores.
• Don't be overly concerned at heating up the glass. It's tempered and hard. It'll be far hotter from a 50W+ bulb than your polishing will ever get it.
• I clamped the fog light wrapped in a towel in a bench vise to firmly hold it.

[wizechatmgr]

Enormous difference. *Adds to his list of important posts*

[sleddriver]

Update:

Using the drill press with a spindle speed of 2650 RPM and a 6" H&L medium backing plate made a HUGE DIFFERENCE in the finished quality and greatly reduced both time & effort required to get fantastic results! What a long way I've traveled since my first effort last year. I'd benched this project out of frustration and needing to move on to other tasks.

I began with the lens that was badly pitted, as shown above. Using the drill press, I moved through 100, 150, 180, 220, 320 and 400 grit. With each grit change, I rotated the lens 90° so I could be sure the scratches from the previous rougher grit were all removed. I didn't have 600 nor 800 H&L paper, so I temporarily tacked some w/d 600 grit to another backing pad using 3M Spray 70 contact cement. The results to this point looked much clearer than the work on the other lens. The light reflection was much sharper, the haze was much lighter plus it only took about 30min to get to the same point vs. hours previously.

At this point, I decided to go straight to the white cerium oxide paste using the 3" foam pad. I mixed it to a consistency of yogurt. The higher spindle RPM of the drill press made a noticeable difference in effectiveness and within a few minutes, I had achieved water-clear glass!

Volvo_Fog Lights 001.JPG (158.62 KiB) Viewed 1873 times

Volvo_Fog Lights 002.JPG (139.5 KiB) Viewed 1873 times

Volvo_Fog Lights 005.JPG (157.08 KiB) Viewed 1873 times

That's quite a difference compared to the first two photos!

Enthused, I re-worked the other one. I started with 320, then 400 & 600. After cerium oxide, it shined as bright as the other:

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Volvo_Fog Lights 007.JPG (173.47 KiB) Viewed 1873 times

Volvo_Fog Lights 008.JPG (156.72 KiB) Viewed 1873 times

YES!!

Tonight, I'll apply the XPEL film, let it cure, then install the fog lights tomorrow! So pleased to have finally achieved these results after such initial frustration! Looking forward to finally having FOG LIGHTS on the sled + new HDLT reflectors!

[bmdubya1198]

Wow, those look great! I'll have to do this eventually. Mine are a little cloudy.

[sleddriver]

Wow, those look great! I'll have to do this eventually. Mine are a little cloudy.

I'll bet there are a LOT of pitted glass fog lights from '98 out there. Following these steps, one can easily refurb them and have them shiny again!

[erikv11]

Looks fantastic! Thanks so much for putting in the effort, and documenting it. I am interested, is this the correct summary:

- drill press 2500+ RPM (e.g. 2650)
- 6" H&L plate (or use spray adhesive) for drill chuck
- mount the light/lens in vise so it is parallel with plate surface
- 100-150-180-220-320-400-600-800 grits (is there water involved here?); rotate lens 90˚between grits
- Cerium oxide paste with 3" foam pad on drill press, for polishing

Do you move the lens surface around as you use one grit, or just bring the drill press down a couple times, then rotate lens, and go on to the next grit?

I see the CeO2 powder on Amazon. It will be a little spendy for me too accumulate all of the supplies but I might try it on the front surface of my 850 fogs.

[sleddriver]

To Erikv11

• You don't need a vise when using a drill press; I used my hands.
• I did spritz the glass occasionally to clear the swarf.
• I also used a gummy sanding belt/pad cleaner occasionally to clean the pad of glass. These look like a huge, tan eraser.
• The 3" foam pad works well for the small lens. You can also use a felt pad, but they're more expensive.
• I definitely move the lens around with my hands and use one edge of the rotating pad to do most of the work.
• I don't think the lens is completely flat, but rather curved.