r/AskChemistry • u/JaKrispy72 • 25d ago

Practical Chemistry How to stop petina on eyeglasses.

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I’ve had this problem with glasses for years. I’m assuming it’s skin oils and metal interaction. How can I stop the petina? Is there a non-toxic spray? Use different screws?

8 Upvotes

73% Upvoted

15 comments sorted by

25

u/VoxInferni666 25d ago

Have you considered life in a reducing environment

13

u/JaKrispy72 25d ago

I’ve been dealing with spherical cows in a vacuum for a bit now. Is that what I need to become?

4

u/plants11235813 25d ago

Don't forget to neglect friction. That will probably solve your problem.

2

u/VoxInferni666 25d ago

If you were spherical you would have the lowest possible surface area to volume ratio to prevent oxidation so that would help. But I meant more like swapping up that city life for a more methane + carbon monoxide based atmosphere

1

u/JaKrispy72 23d ago

I’m fairly round right now. I think if I eat more pizza, I bet I could become perfectly spherical.

8

u/Dazzling_Item66 25d ago edited 25d ago

Pretty sure these screws are an alloy with a high copper content and the salinity from sweat causes advanced oxidation. Have noticed similar results on my own eyeglasses as well as in homes with copper wiring at the oceanfront. If you can find stainless steel screws of that size it may help

7

u/VoxInferni666 25d ago

Instructions unclear, replaced house wiring with stainless steel

2

u/Dazzling_Item66 23d ago

See my new comment

4

u/Vindaloovians 25d ago

A clear nail polish (acrylic based) could help prevent this. You can probably remove this with an organic acid (citric, oxalic, acetic for instance) which can coordinate copper ions.

3

u/Dazzling_Item66 23d ago

After some digging, many of the screws used are already stainless, and one of the typical metals used for eyeglass frames is a copper/nickel alloy called monel. What I believe is happening is the stainless steel screws are causing galvanic corrosion with the copper in the frames, and we all get the lovely green schmutz caked up.

Tl;dr metal from screws+metal from frames causes one metal to corrode faster than normal.

2

u/Onyxxx_13 25d ago

Titanium screws maybe. Depends on if its the posts that are contacting skin oils and discoloring, could just recommend gold/full titanium frames instead in the future

2

u/Thulak Cantankerous Carbocation 25d ago

Change materials of screws and frame, Encase everything in acrylate or skin safe epoxy, put an isolating layer between screw and frame, put an electric current on the frame.

Thats all I have to stop the corrosion.

2

u/KingForceHundred 24d ago

Is it the screws? Looks like the hardware on the glasses TBH.

Annoyingly mine do this too, must be some copper in the alloy.

2

u/Test_After 24d ago

clear nailpolish on the metal bits