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Old 23-01-2025, 08:24   #1
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Plexiglass / Perspex polishing and finishing

Does anyone have any experience in using a clear coat (headlight UV protector or similar) on plexiglass. Any liquid that will fill in the micro scratches will reduce the difference in refractive index and consequently make the scratch disappear. The question is how long will it last and in three months will it be much worse. A small percentage of the reviews on amazon suggest this may be the case.


Second question:
Has anyone finished / polished their plexiglass /perspex windows, port holes or hatch covers to close to near perfect clarity? Such that it wouldn't require a clear coat.



I have spent a lot of time trying to get my windows near perfect. I have succeeded in not bad but there remains a slight haze. When viewed under a magnifying glass, there
are millions of tiny semi-circular scratches that don't come out with compounding. This is annoying the crap out of me.
I am happy to detail what I have tried but it is a long list so I will wait to see if anyone is interested.


thank you for your assistance.
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Old 23-01-2025, 13:28   #2
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Re: Plexiglass / Perspex polishing and finishing

I am interested.
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Old 23-01-2025, 14:09   #3
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Re: Plexiglass / Perspex polishing and finishing

I’m interested too. “OFF” bug spray damaged mine.
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Old 23-01-2025, 15:40   #4
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Re: Plexiglass / Perspex polishing and finishing

This is the very short version of the process. I have been trying various methods and materials for almost a month. If anyone has any suggestions I am very receptive.



Equipment 6 inch duel action random orbital buffer /polisher from Harbor Freight (HF).
corded electric drill.


Purchased, tried and don't need or didn't add anything

forced action random orbital buffer / polisher
3M Perfect-it numbers 1,2,3 These are supposedly what most detailing shops use but the 3M system requires buying a $500 dollar buffer. I used it with the Grant's pads which may be contributing to the problem. I don't know. I am amenable to buying higher quality pads if anyone really thinks this may be the issue. I am not going to buy the 3M buffer. I don't plan on opening a body shop although I now have more than 300 sanding discs so I have a good start.



Process

Clean window very thoroughly. Go over entire surface with a razor blade to pick up anything that could get caught in the sanding material. This can be done with detailing putty but I didn't have any.



3M 800 grit sandpaper dry then wet

duragold brand 1000, 1500, 2000, 3000 very wet - continuously irrigated sanding. stop frequently to make sure there is no buildup on the sanding disc. Clean disc with a clean wet cloth. Even the smallest bit of stuff can result in a huge mess.



HF headlight restoration kit 1500 grit sanding pad wet around the edges using electric drill.
HF headlight restoration kit polishing pad with cutting / polishing paste over entire surface.



3m Perfect-it polishing compound on grant's fine polishing pad (black)


This last step appeared to make little difference. Under the magnifying glass you can still see millions of semi-circular marks. Very fine but enough to make the window look slightly cloudy when viewed from certain angles from inside. Repeated this step several times but it didn't seem to change anything.

Note from the outside the window looks pristine and a normal sane person would call it good. I am not a member of that group.


Things to avoid.
HF sandpaper lasts about 2 minutes before it starts to accumulate crap and make scratches.

HF sanding discs film type. at about 90 seconds film starts to ball up and make deep scratches required going back to 600 grit to get them out.
HF/Grant's foam backed sanding discs 2000 and 3000 grit. Destructed in under 2 minutes.


Grants Blue compounding pad. Not sure about the yellow pad. Black seems okay.
Initially used a RODA 5 inch vacuum type buffer polisher with holes in the pad. Went from 300 to 5000 grit but there were many pigtails. I figure this is because sanded dust accumulates at the edges of the holes. But I could be completely wrong.
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Old 23-01-2025, 19:19   #5
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Re: Plexiglass / Perspex polishing and finishing

In the past I have tried to polish headlights on cars and perspex on boat windows. Like you did, first with wet sanding to 2000 grid, then with 3M 1-2-3 compounds.
Yes, it looked good, so much bettter than it was before. I used a MIlwaukee 7" / 180 mm buffer model M18FAP180, but a Makita corded unit would also work very well, ie model 9237CB. I used that one before switching to cordless Milwaukee.

However the finish might not be up to your standards.....
And...... I might not do that again either, as the good finish last about a season. Reason for that is, I am told, new Perspex has a thin layer of hard UV protection on the acrylic. When sanding and polishing that layer is removed. And this layer is only present on better quality acrylic?
Anyway, I installed new acrylic the season after that. Good for at least 10 years, maybe 20

Later on a friend's boat, I tried to use No.3 (the finest) only, but that did not get rid of the scratches and discoloration. Maybe the finest compound only to be used before the acrylic gets really bad. But who would be willing to do that while the acrylic is still about right?
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Old 23-01-2025, 20:43   #6
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Re: Plexiglass / Perspex polishing and finishing

Our acrylic is due for replacement. I am thinking about tempered glass.
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Old 24-01-2025, 06:15   #7
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Re: Plexiglass / Perspex polishing and finishing

Hankonthewater: Did you use any of the UV clear coats that usually come in the headlight restoration packs?


Do you have a link or some other reference that addresses the UV layer on plexiglass. That might explain a lot of what I am seeing.
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Old 24-01-2025, 08:20   #8
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Re: Plexiglass / Perspex polishing and finishing

MAKROLON suggests the NOVUS brand polishes, and I have found them to work fairly well.
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Old 24-01-2025, 08:28   #9
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Re: Plexiglass / Perspex polishing and finishing

Quote:
Originally Posted by Seapig View Post
Hankonthewater: Did you use any of the UV clear coats that usually come in the headlight restoration packs?

Do you have a link or some other reference that addresses the UV layer on plexiglass. That might explain a lot of what I am seeing.
I purchased over the years 2 lots of headlight cleaners. I cannot recall if it had a UV coating to apply, I cannot remember and my memory is still intact, so I guess there was not.

Many many years ago I shared my workshop with 2 other businesses, a plastic fabricator/welder and a fibreglass shop. On occasions I helped them with labour, and got to know those businesses fairly well. That is where I got the information on acrylic UV coating. Let me find out a bit more.
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Old 24-01-2025, 11:54   #10
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Re: Plexiglass / Perspex polishing and finishing

I don't know if this is of interest or if it works but I read an article recently about cleaning Acrylic aquarium tanks using "Magic Sponge" the white Melamine sponges.
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Old 24-01-2025, 12:55   #11
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Re: Plexiglass / Perspex polishing and finishing

I did this about 15 or so years ago using just toothpaste and an electric toothbrush


https://www.youtube.com/results?sear...+syncromeister
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Old 24-01-2025, 13:05   #12
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Re: Plexiglass / Perspex polishing and finishing

Leadfree et al.,
did you use the Novus specifically on Markrolon polycarbonate?


When you say fairly well, that is close to condemning with faint praise. would you care to elaborate, what did you like what didn't etc.
Did it give you a surface that was second in smoothness to only the James Webb deep space telescope.


Does anyone have any opinions on using glass polish on plexiglass? The stuff I have been looking at is called Sonax and it's magic ingredient is cerium oxide which according to those wonderful folks at wikipedia is also known as optical rouge.
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Old 24-01-2025, 15:44   #13
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Re: Plexiglass / Perspex polishing and finishing

I've worked with acrylics for many years.

I've bent, routered, cut, flamed, welded, and polished hundreds of pieces.

Many years ago I was working with a very large and costly piece of clear acrylic that got a huge scratch. It was a scratch deep enough for your fingernail to catch... very deep.
I was able to polish it out using very fine wet sandpaper 2000-5000, then used the 3 Novus polishing compounds. It came out perfect.

If your circular defects are actually scratches and not the beginning of crazing, then the sandpaper + Novus polishing compounds will work.

A couple of tips you may want to try (if you can remove the scratches) instead of liquid, use Lamination film like this:

https://madico.com/specialty-films/a...RoCa7UQAvD_BwE

There are some extremely strong films out there that protect acrylics from UV degradation, scratches, etc.
Just remember to order "optically clear" and not "clear"
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Old 24-01-2025, 16:02   #14
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Re: Plexiglass / Perspex polishing and finishing

Admiral31 - you are a lot more patient than I am. An electric toothbrush on my salon windows would take considerably longer than I expect to be on the planet.


Tupia - were the sponges for removing scratches or just for cleaning?


Iron E - does that film act the same way that a clear coat would? In other words would the adhesive fill in the microscratches?



When you sanded out the scratch did you use a buffer or do it by hand?


I found that 3000 grit very wet didn't seem to do much. I kept at it for about 10 minutes (600 strokes with the buffer) and couldn't detect any sanding residue. The 3M rubbing compound took made the surface shiny but didn't get out the microscratches.
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Old 24-01-2025, 17:12   #15
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Re: Plexiglass / Perspex polishing and finishing

Quote:
Originally Posted by Seapig View Post
Admiral31 -


Iron E - does that film act the same way that a clear coat would? In other words would the adhesive fill in the microscratches?
The film acts as a protectant against UV and scratches.
I'm not aware of anything for acrylic portlights that fills "microscratches". The stuff for headlights might look good for a minute, but you're also not trying to look through it as you do a window. I would imagine that liquid across a window would look terrible.


Quote:
When you sanded out the scratch did you use a buffer or do it by hand?
By hand.

Quote:

I found that 3000 grit very wet didn't seem to do much. I kept at it for about 10 minutes (600 strokes with the buffer) and couldn't detect any sanding residue. The 3M rubbing compound took made the surface shiny but didn't get out the microscratches.

Then move to a more abrasive 2000 or 1000, or 600. Then move back up to the finer. Like I mentioned, I use Novus Plastic Polish 1,2,3 for polishing acrylic. You can google it.

I'm wondering if you're not dealing with a Crazing issue. This cannot be polished or sanded out. They are actual cracks that many people mistake for scratches.
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