Author Topic: Cracking and Crazing of Old Lenses  (Read 104 times)

rparker

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Cracking and Crazing of Old Lenses
« 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
77' W116 280S, 4-Speed Manual

raueda1

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Re: Cracking and Crazing of Old Lenses
« Reply #1 on: Yesterday at 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/
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,
-Dave
Now:  '76 6.9 Euro
Before that:  1966 230S, 1964 220SE coupe, 1977 Carrera 3.0

daantjie

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Re: Cracking and Crazing of Old Lenses
« Reply #2 on: Yesterday at 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
Daniel
1977 450 SEL 6.9 - Astralsilber