Headlight Hologram Mystery

[tattooman]

Headlight Hologram Mystery


So, I did some headlight restoration a couple days ago (remember please I'm new to detailing). The lenses were moderately cloudy starting out. So I wet sanded with 800, 1500, and 2000. Then I used M105 with a 3 inch orange foam pad with a PC 7424xp, followed by M205 with a pink 3 inch foam pad. The problem is that after a final IPA wipedown, I saw a hologram in one of the headlights. So I went at it again with 205, but it wouldn't come out. It wasn't severe, and I was running out of time, so I sealed them up with JetSeal and called it done. I told my friend I'd research it and address it later if I could figure out what I did wrong, even though he doesn't really care, he's glad his headlights are clear for the next state vehicle inspection. So anyway here are my questions:


1. Was that thing actually a hologram ? If it was a hologram it seems I could have polished it out with the 205, which didn't work.


2. If it's not a hologram, is there anything in restoring headlight lenses that looks like a hologram but actually isn't ? If so what is it ?


3. If it's not a hologram, is it possible it could be something inside the plastic lens itself, ie, not on the surface ?


4. Could it be heat damage from me, by concentrating too much pressure for too long with the 3 inch pad ? It did get slightly warm, since I was putting my hand on the pad periodically to check the temperature.


5. Whatever else.

Any advice or analysis is much appreciated.

[Route246]

I would start over. I had this happen and it was because my original sanding (I used 1000 for the original, you are using 800) was not thorough enough.

[brettS4]

I agree with Route246. I had a similar issue with my Audi headlights a couple years ago. I had to go back to wet sanding to get rid of the holograms. After that, and M105/205 it came out perfect.

[Mantilgh]

It could be a couple of things.

Could be leftover sanding marks from a lower grit that were not completely removed with the following grit.

It could be that you need a compound and a more aggressive pad to remove the 2000 grit sanding marks, M205 may not have enough cut.

There could also be defects that are deeper in the surface, outer and inner, if the lights are old or neglected.

I think I’d go with a compound and a cutting pad first, then follow up with a polish and polishing pad and see how it looks from there.

[DBAILEY]

Was the sanding by hand or with a drill?

[Route246]

Was the sanding by hand or with a drill?

That's a good point. I quit using the drill. Too much cut and swirling, etc. Hand sanding should be sufficient to cut most plastic. 800 should also be sufficient.

[DBAILEY]

Same here. The drill had a tendency to leave a few deep swirls despite my best efforts to keep the pad level. I have had to drop down to 400/500 grit on some Audi headlights. They have the toughest headlight lenses I have ever worked on.

[tattooman]

Was the sanding by hand or with a drill?

By hand using a small piece of closed cell foam backing for consistent pressure. only sanded lightly in straight lines. I couldn't imagine using a rotary sanding device on plastic, sounds like suicide, even though I know some headlight kits use that method. I would think that could cause more problems than it solves.

[tattooman]

I agree with Route246. I had a similar issue with my Audi headlights a couple years ago. I had to go back to wet sanding to get rid of the holograms. After that, and M105/205 it came out perfect.

Sounds like a good plan guys, thanks. Just to add, that side with the hologram was sanded by my buddy using the same grits and technique I was using on my side of the vehicle. Maybe he did something that caused the hologram that I didn't do, who knows. One thing, when I start over on that side, I should only have to sand the area with the hologram, that will save some time and elbow grease.