Poly lens "fogging"

[The Mighty Mutt]

Hello peoples! I'm wondering if anyone else here has experienced this little annoyance. For anyone that hasn't, we occasionally do remakes for customers that bring in these lenses that look, well, foggy. It's always poly lenses. (never trivex, so I don't think it's the UVNV). The best way I can think to describe it is it looks like it does after you breath heavily on the lens. You can't actually feel a different texture on the front or back surface of it. We have sent some of these to our specials lab, they don't know what it is either. The length of time of ownership varies from 5 months to almost 2 years. Care and treatment of the lenses doesn't seem to be a common factor (some clean them only with whatever is handy, some only with a microfibre cloth.) For a while I noticed we got a lot more of these in the warm seasons, so I thought that maybe these were people that left them in a hot car all day in direct sun light. But lately, that doesn't seem to be the case. Does anyone know what might be causing this?

Thanks for any help!
~The Mighty Mutt

[gunner05]

Be sure they aren't cleaning their lenses with an ammonia based cleaner, ie windex.

[Chris Ryser]

Does anyone know what might be causing this?

Good brand polcarbonate lenses have a hard coat on the + and the - side which protects the lens not only against scratching but also seals the surfaces against penetration of chemicals or vapours.

However the edges after having been cut and edged are not coated anymore.

Polycarbonate when attacked by unfriendly chemicals, such as solvents will start a chain reaction as for example as crazing all over, go dull and more. (Acetone, alcohols like methanol, IPA and others)

There are only 2 possibilities by which these lenses will get damaged, either through a poor hard coat on the surface or through penetration at the unprotected edges.

The most common culprit would be your run of the mill lens cleaner as sold by most opticians and drug stores.. Over 95% of lens cleaners sold are made with 30% Isoprpyl alcohol or methanol mixed with 70% water. This is an age old formula and has cleaned lenses for the last 100 years from glass to plastic.

One should make sure to advise customers wearing polycarbonate lenses not to buy and use lens cleaners made with alcohols, but to only use products made with surfactants in a water base. They can also be cleaned with a gentle soap solution and water without danger to their chemical composition.

CR39 is totally insensitive to most chemicals as solvents and acids, but some of the newer plastic materials can react to them. Unprotected polycarbonate is the worst of all of them.

This would make people wearing polycarbonate lenses in rimless frames, as well as any regular frame a prime target if they work in an environment containing vapours or fumes from solvents or alcohols. There are countless jobs that will get that exposure as for example a painter, auto-body shop , printing and hundreds more.

[Rory Ramig]

Hello peoples! I'm wondering if anyone else here has experienced this little annoyance. For anyone that hasn't, we occasionally do remakes for customers that bring in these lenses that look, well, foggy. It's always poly lenses. (never trivex, so I don't think it's the UVNV). The best way I can think to describe it is it looks like it does after you breath heavily on the lens. You can't actually feel a different texture on the front or back surface of it. We have sent some of these to our specials lab, they don't know what it is either. The length of time of ownership varies from 5 months to almost 2 years. Care and treatment of the lenses doesn't seem to be a common factor (some clean them only with whatever is handy, some only with a microfibre cloth.) For a while I noticed we got a lot more of these in the warm seasons, so I thought that maybe these were people that left them in a hot car all day in direct sun light. But lately, that doesn't seem to be the case. Does anyone know what might be causing this?

Thanks for any help!
~The Mighty Mutt

I have seen a foggy poly lens come back in once in awhile.
My guess is that after the lens was ground somebody forgot to apply the backside hard coat. The exposed polycarbonate surface will scratch with the most soft cloth they make. Experiment with a stock poly lens that will surly have a scratch coating applied. Put a single drop of water on both lenses (approximate curve). There will be a difference in how the water drop beads up or tends to spread out across the lens.