Messed up Headlights

[Ducktail]

tl; dr version: Numerous attempts to restore clear plastic headlight lenses to like-new finish result in massive fail. About to commit suicide.

So the story started when I took apart a BMW 6 series headlight that had developed a crack leading to condensation inside the headlight. The headlight was leaking badly and all sorts of sand/condensation gathered up inside. We sealed the leak (luckily in the headlight housing, not the clear lens) and while we were at it, we decided to clean the headlight thoroughly. Unfortunately, my friend decided to clean the plastic headlight lens with car wash soap, thinking it would be safe for the clear finish. To my surprise, the plastic developed some nasty water spots from the inside and became quite hazy. Well, we were going to sand down the headlight to remove the oxidation and yellowing anyways, so I didn't think that removing the haziness was going to be a challenge. Boy was I wrong...

I started the process to remove yellowing, oxidation, and pitting from both sides of the headlight's plastic lens, since I had the headlight completely dissembled at this point. I dry sanded the headlight with 320 grit sandpaper, and then proceeded to 500 grit. After that, I wet sanded all the way from 800 to 1000, 1500, 3000. I kept checking the progress taking my time between all these steps, both inside and outside surfaces of the plastic lens was smooth, but we still had haziness and light swirl marks (the swirl marks are only visible in direct light).

After I finished sanding, I applied some Meguiar's 105 cutting compound, with a Griot's Garage 3" Random Orbital polisher set on high-speed (5-6) and then some 205 compound also set on high-speed. All sanding/polishing was done with the polisher. Low speeds were used for sanding, high-speeds were used for polishing. Pressure used throughout all the steps was medium pressure. I am cleaning after each sanding process and taking my time to remove all previous scratches I could notice.

My issue: The headlight still looks like crap. The yellowness and extreme haziness is definitely gone. But the headlight now has some sort of slight haziness all over it. Like condensation just starting to build up. The plastic is NOT 100% clear and has a lot of swirl marks the moment you shine some light on it. Most of the big scratches from road debris are gone. A side by side comparison with a "good" headlight from the same car, shows what I mean (see picture below). I repeated the process 4 times on both sides (which equals 8 times). I researched thoroughly, and I took my time sanding over and over again, but the result only marginally got better.

Product & Equipment Used:
* Griot's Garage 3" Random Orbital Polisher
* 3M 3" sandpaper discs (grits: 320, 500, 800, 1000, 1500, and 3000)
* Meguiar's 105 and 205 compounds
* Meguiar's PlastX
* Buffing & polishing pads

[Setec Astronomy]

Wait a minute--after you finished the first time and noticed the haziness, you went back and started over again with 320 grit?

What kind/brand of sandpaper are you using?

[Ducktail]

Wait a minute--after you finished the first time and noticed the haziness, you went back and started over again with 320 grit?

What kind/brand of sandpaper are you using?

No, I used 500 and finer grit in the first 3 trials. I noticed no improvement in these trials. Then, I decided to start fresh with 320 grit. So in total I used 320 grit two times in 8 attempts (2 were 320 to 3000 and 6 were 500/800 to 3000)

I am using 3M 3" Sanding Discs Hookit Gold, Purple..etc (depending on the grit).

[Setec Astronomy]

Once you've got the yellow and the scratches out, there's no reason to go back to the 320 or 500, and probably not the 800, because you're just working backwards by putting sand scratches back in.

Now, after that...3M makes a bazillion different kinds of sandpaper, you have to make sure you are using the controlled grit. I am set up to do the same thing as you, but I haven't done it yet--but I went with all Meguiar's Unigrit discs.

[Audios S6]

Can you see the difference between a swirl and a pigtail? If you are using a DA, you can still get swirls, but you should be seeing pigtails too. If not, then you should rethink how you are wiping off the sanding residue and the M105 & M205. You may be putting the scratches back in yourself.

As you go through the sanding steps, expect to spend more time on each step the higher grit you go. You need more time using less cut to remove the scratches from the previous step.

this is for clarification and not to be taken literally:
320 grit = x time
3000 grit = 5x time

[top189h]

I hate to say it, but you may need a rotary to get the haze out. I tried a couple of times to do restorations with my gg6 with a 3 inch backing plate and I for the life of me couldn't get them perfect. I moved up to a rotary with a 3 inch wool pad and finish with my gg da and haven't had an issue since. I'm sure some people can do it with a da, but in my experience I have never been able to.

[Ducktail]

Once you've got the yellow and the scratches out, there's no reason to go back to the 320 or 500, and probably not the 800, because you're just working backwards by putting sand scratches back in.

I agree about this point, makes total sense.


Now, after that...3M makes a bazillion different kinds of sandpaper, you have to make sure you are using the controlled grit. I am set up to do the same thing as you, but I haven't done it yet--but I went with all Meguiar's Unigrit discs.

Could you please elaborate about this point?

These are my sanding discs:
320- Amazon.com: 3M 30275 Hookit Purple 3" P320 Grit Clean Sanding Disc: Power & Hand Tools (http://www.amazon.com/3M-30275-Hookit-Purple-Sanding/dp/B003TQF5RU/ref=sr_1_2?s=power-hand-tools&ie=UTF8&qid=1437511581&sr=1-2&keywords=3M+hookit)

500- Amazon.com: 3M 30272 Purple 3" P500 Grit Clean Sanding Hookit Disc: Automotive (http://www.amazon.com/3M-30272-Purple-Sanding-Hookit/dp/B003XNE124/ref=pd_bxgy_263_text_y)

800- Amazon.com: 3M 30260 Purple 3" P800 Grit Clean Sanding Hookit Disc: Automotive (http://www.amazon.com/3M-30260-Purple-Sanding-Hookit/dp/B004MEF4C4/ref=pd_bxgy_263_text_y)

1000- Amazon.com: 3M 02091 Trizact Hookit 3" P1000 Grit Blending Disc: Automotive (http://www.amazon.com/3M-02091-Trizact-Hookit-Blending/dp/B004MED9YY/ref=pd_sim_263_3?ie=UTF8&refRID=01VDSWAWXAHGDGAR1F61)

1500- http://www.amazon.com/3M-02094-Trizact-Hookit-Sanding/dp/B005RMZQLY/ref=pd_sim_263_5?ie=UTF8&refRID=0F42M42RWNPG0ZYTVNF7

3000- http://www.amazon.com/3M-02087-Trizact-Hookit-P3000/dp/B002M1PEHE/ref=pd_bxgy_263_text_z

[Ducktail]

I hate to say it, but you may need a rotary to get the haze out. I tried a couple of times to do restorations with my gg6 with a 3 inch backing plate and I for the life of me couldn't get them perfect. I moved up to a rotary with a 3 inch wool pad and finish with my gg da and haven't had an issue since. I'm sure some people can do it with a da, but in my experience I have never been able to.

You have a point here, I bought the GG DA polisher as a quick tool to help me. Its not my main tool (Which I haven't bought yet).

But for god's sake I've seen some people here in the forums sand them manually with their hands and still get excellent results!

[Setec Astronomy]

Could you please elaborate about this point?

These are my sanding discs:

You're going to get in trouble for those links.

Elaborate...well, the grit on sandpaper has a tolerance. So, if you have a 3000 grit disc, the nominal grit size is 3000, but you might have anywhere from 2500-3500. I know 3M has controlled grit papers that are, say, 2900-3100 (I'm just pulling numbers out of the air).

I don't really know where the Trizact falls into this. Meguiar's Unigrit (unigrit--one grit size--get it?) is definitely a controlled-grit paper. 3M really makes too many products to be able to figure it out--I can't. That P3000 disc didn't even show up on their website--it showed up on 3M collision.

[Ducktail]

You're going to get in trouble for those links.

Elaborate...well, the grit on sandpaper has a tolerance. So, if you have a 3000 grit disc, the nominal grit size is 3000, but you might have anywhere from 2500-3500. I know 3M has controlled grit papers that are, say, 2900-3100 (I'm just pulling numbers out of the air).

I don't really know where the Trizact falls into this. Meguiar's Unigrit (unigrit--one grit size--get it?) is definitely a controlled-grit paper. 3M really makes too many products to be able to figure it out--I can't. That P3000 disc didn't even show up on their website--it showed up on 3M collision.

Sorry for the links, can't edit them. Sorry Forum! New here.

I'll search on where Trizact falls into, but I do not think that these "not controlled grits" will make a difference. Do you think thats the problem with my haziness? (Uncontrolled grits?)

[Ducktail]

Can you see the difference between a swirl and a pigtail? If you are using a DA, you can still get swirls, but you should be seeing pigtails too. If not, then you should rethink how you are wiping off the sanding residue and the M105 & M205. You may be putting the scratches back in yourself.

As you go through the sanding steps, expect to spend more time on each step the higher grit you go. You need more time using less cut to remove the scratches from the previous step.

this is for clarification and not to be taken literally:
320 grit = x time
3000 grit = 5x time

I definitely see swirls. And for pigtails, I can also confirm that I have a extremely fine pigtails.

Do you think I how I remove the polish will affect? I mean I swipe it down with a MF towel very easily.

[Setec Astronomy]

I'll search on where Trizact falls into, but I do not think that these "not controlled grits" will make a difference. Do you think thats the problem with my haziness? (Uncontrolled grits?)

Well, there is a reason why they make unigrit paper, and it's not because it doesn't make a difference.

If you are using your 800 to remove the 500 grit scratches, and the 1000 to remove the 800 grit scratches, and the 1500 to remove the 1000 grit scratches...if you have one 500 grit particle in your 1000 grit paper...then it's going to pigtail the hell out of things, and the 1500 grit isn't going to remove it.

That's just an example, as I said before I don't know what the actual grit tolerance is.

If you were working on an opaque surface, you might not even be able to see the "hazing". Working on a clear lens is going to require the most care.

[Audios S6]

I definitely see swirls. And for pigtails, I can also confirm that I have a extremely fine pigtails.



Do you think I how I remove the polish will affect? I mean I swipe it down with a MF towel very easily.


I'm mostly trying to eliminate potential problems. Pigtails indicate that you are:

1. Not removing all the previous scratches from the previous step

OR

2. Not cleaning residue well enough/working clean

OR

3. Not using appropriate type of paper as Setec alluded to..


Swirls can be the same causes, but also because you put in defects after you finished it out.

[g35_coupe]

Did you wetsand the inside as well? I surely hope not.

[Ducktail]

Did you wetsand the inside as well? I surely hope not.

What do you mean by that?
Yes I did wetsand the inside and outside..