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Garage => Interiors & Exteriors => Topic started by: rparker on 25 November 2021, 02:50 AM

Title: Cracking and Crazing of Old Lenses
Post by: rparker on 25 November 2021, 02:50 AM
Good day,
1. I'd like to firstly ask what type of plastic these lenses are made from?
2. Is it possible to "Save" them if they are already in this state, it looks like many internal cracks but me handling them, they still feel very solid. It'll almost be a waste to throw these away. Has anyone tried to save them or am I just wasting my time?

Cheers.

Ryan
Title: Re: Cracking and Crazing of Old Lenses
Post by: raueda1 on 29 November 2021, 08:10 AM
I've also wondered about the material.  IMO likely candidates are PMMA (aka acrylic aka "plexiglass"), PC (polycarbonate) or maybe SAN (styrene acrylonitrile).  I'd guess PMMA but I really don't know.  Anyway, I greatly doubt there's much to do about the crazing, which seems to be on the inside of the lens.  You might try applying a thin coating of windshield repair resin over the crazed areas.  This seems to be a low viscosity acrylic that's drawn into the glass cracks.  Try on a small inconspicuous area to make sure it doesn't frost or haze the surface.  If you go this route please report back on the outcome!

There's also this: https://forum.w116.org/interiors-and-exteriors/polishing-rear-tail-light-lenses/ (https://forum.w116.org/interiors-and-exteriors/polishing-rear-tail-light-lenses/)
I haven't tried it yet, too low a priority, but rparker seemed to have good results from the Novus products.  But that's just for polishing the outside - I greatly doubt it would help with the deeper cracking on the inside.  Good luck and cheers,
Title: Re: Cracking and Crazing of Old Lenses
Post by: daantjie on 29 November 2021, 09:30 AM
Personally I would source new ones on ebay.  They pop up all the time.  I once lucked out and bought a NOS one for a dollar on ebay auction ;D
Title: Re: Cracking and Crazing of Old Lenses
Post by: rparker on 30 November 2021, 08:30 PM
Personally I would source new ones on ebay.  They pop up all the time.  I once lucked out and bought a NOS one for a dollar on ebay auction ;D

Yup, have done that already, however I used this piece as a trial for that "Headlight" restorer and thoroughly cut and polished it. As you can see from the photos, it really worked and now I feel bad throwing it away, it catches the light beautifully crisp but so does the crazing....  :-\