be careful with plastics

[autokunst]

Hello all,
Writing to post what NOT to do. I was cleaning up my rear fog light lens. After much time spent carefully removing old gasket material and applied silicone, I noticed that the inside of the lens appeared to have a light mist of over spray making the clarity a bit lacking. I grabbed the first chemical within reach to try to clean it - acetone. A short while later, I realized the error of my ways as the acetone severely clouded the plastic. :eek: And because this is on the inside of the lens with all of the texture, there is no way to sand it out I'm afraid. Lesson learned. Hopefully this post will save someone from repeating my mistake.

 

[JFENG]

If you wet it and it clears up then you can fix it by spraying the inside with clear paint. As far as physical removal, how about some aggressive paint cutting compound and a grey scotchbrite pad?

 

[autokunst]

Thanks John. Unfortunately, wetting it does absolutely nothing. I really roached it.
I'll try cutting it with compound and a pad tonight. Else, I'll likely be in for a replacement part from W&N... At least that solution will also solve the gaskets that I'd need...

 

[jmackro]

Acetone is a pretty strong solvent, though I doubt that any solvent would dissolve hardened paint (e.g., your overspray) without also attacking the plastic. bfeng's idea of using abrasives (rubbing compound, Scotchbrite, etc.) are probably the best approach. That might also minimize the effect of the crazing.

 

[Wladek]

Stephen - your situation is not the best, but try first gentle wet sandpaper like 500, 1000, 2000 & then use polishing compound for plastics (i use for couple years Meguiar's PlastX & for sure can recommend it).

Clear coat on plastic will look good at the beginning, after some time it will just make more sh.t.

 

[teahead]

Can get a new setup, but not cheap:


https://www.ebay.co.uk/itm/162661521265?rmvSB=true

https://parts.bmwmonterey.com/p/BMW_1973_30CS/Rear-fog-light/43849863/63241353254.html

https://www.ebay.com/itm/Genuine-BMW-E9-NK-Coupe-Rear-Fog-Light-OEM-63241353254-/192291773041?_ul=AR

https://www.getbmwparts.com/oem-parts/bmw-rear-fog-light-h63210-63241353254

 

[duct-tape]

if it's truly bodged, try hitting it [gently] with a heat gun and see if you can "smooth" out the haze

 

[deQuincey]

i really dislike acetone,... !

 

[autokunst]

i really dislike acetone,... !

Well, I think I may have to agree. It is great for clean (tig) welding - wiping down steel after any scale is removed for a contaminant free (reduced) weld. But on plastic...

 

[Arde]

A 2017 study concluded that of the 9.1 billion tons of plastic produced since 1950, close to 7 billion tons are no longer in use.
The problem is plastics, acetone and toluene are the solution.

Stan, can you make us glass taillights please?

i really dislike acetone,... !

 

[Wladek]

Acetone also can make little cracks on transparent plastic edges.
Last year was cleaning plastic badge from dirt & was badly surprised - badge land in garbage.

 

[restart]

Lacquer thinner, polish and wax

 

[nosmonkey]

Brake fluid works a treat on overspray on plastic parts.

 

[restart]

Love me some science and art!

Lacquer thinner also works on overspray. I think Blending spray I see slightly diluted lacquer thinner.
Here is lacquer thinner and brake fluid

The lacquer thinner does not even need polishing.

It takes the acetone just over a minute to whiten.

 

[autokunst]

Wow - this is a real time science experiment. Thank you for posting this test and results. I will certainly try the lacquer thinner - not sure to what extent the textured/irregular reflector will disrupt these results. I assume you are "wiping" the thinner on/into the part (essentially wiping the white cloudiness off)?

 

[JFENG]

Brilliant!!

 

[restart]

Brilliant!!

Marry me!-))
Keep the acetone in a spray bottle in the shop.

 

[autokunst]

Just wanted to close the loop on this issue. @restart gets a gold star for chemist of the year! The lacquer thinner removed just about all of the white chalky haze that the acetone caused. I was certain the white was forever ruined plastic, but the lacquer thinner erased almost all of the damage I did. Quite miraculous - I might start bathing in it. Thanks for the tip!!!

 

[Gary Knox]

Stephen,

Having spent a good bit of time in Chemistry labs, I once concluded there were two liquids that between them were pretty close to universal solvents. One was good old water, which our bodies use for putting lots of stuff in solution, and a lot of other chemicals as well. The other is Ethyl Methyl Ketone, which is commonly called lacquer thinner. It dissolves almost anything that is insoluble in water! Just be careful with plastic, as many of them will disappear in it. Also, DO NOT bathe in it (says I, who probably used it to clean stuff off my hands 60-65 years ago).

Glad it worked for you.

Gary-

 

[dang]

My typical process when cleaning something is starting with isopropyl alcohol.... didn't work, then lacquer thinner..... didn't work, then acetone. If it doesn't clean with acetone it's probably going to take something physical and/or mechanical to clean it.