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Thread: Why do lenses craze?

  1. #26
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    Quote Originally Posted by ml43 View Post
    But the hydrophobic/oleophbic layer can be reapplied in a minute or so. Yes as good as new.

    The AR part is the most expensive/hardest part to reapply.
    While this may be true to a point, this is faulty logic for two reasons. 1) Once those layers are gone/damaged the AR stack itself is vulnerable to a myriad of real life chemical contaminants and abrasive gritty substances that will permanently damage it - in the non sterile AR lab environment that my face cheese faithful meander in daily.

    2) The AR may be the most expensive part of the process, but I can get a cheap AR stack applied to a lens for 20 something dollars. The best of the best ARs (which I deal in almost exclusively) are pushing 3 to 4 times that amount. If the extra coating processes these were put through equated to a simple siloxane dip coating a la Chris Ryser they would not cost so much, nor would there be such a difference in scratch/chemical resistance among them all.

    Again, advise your clients in your way, I will tell them to use soap and water, or my lens cleaner. If that doesn't work I ask them to bring the lenses to me for the use of harsher chemical agents.

  2. #27
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    Quote Originally Posted by Tallboy View Post
    While this may be true to a point, this is faulty logic for two reasons. 1) Once those layers are gone/damaged the AR stack itself is vulnerable to a myriad of real life chemical contaminants and abrasive gritty substances that will permanently damage it - in the non sterile AR lab environment that my face cheese faithful meander in daily.

    2) The AR may be the most expensive part of the process, but I can get a cheap AR stack applied to a lens for 20 something dollars. The best of the best ARs (which I deal in almost exclusively) are pushing 3 to 4 times that amount. If the extra coating processes these were put through equated to a simple siloxane dip coating a la Chris Ryser they would not cost so much, nor would there be such a difference in scratch/chemical resistance among them all.

    Again, advise your clients in your way, I will tell them to use soap and water, or my lens cleaner. If that doesn't work I ask them to bring the lenses to me for the use of harsher chemical agents.

    you do realize that the difference between a house AR and "crizal" and the like is mostly just a name and marketing.

    most labs only have one AR machine.

    house AR and crizal is done by the same machine. the only real difference is the crizal coatings line essilors pockets.

    like wise with the hydrophobic/oleophobic coatings.

    yes ones that are done in chamber do last a bit longer and have slightly better QC. but I bet if I didn't tell you the difference, you wouldn't be able to tell the difference between a crizal AR and a brand A AR.

    Chris isn't the only on that sells and uses wipe on hydrophobic/oleophobic coatings.

    almost all jobs that come from eyemed use wipe on hydrophobic layers.

  3. #28
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    Originally Posted by Craig We use alcohol every day to clean the lenses; it works great and does not effect coatings. We us the strong stuff as the weak does not work. The lab cleans the lenses with alcohol as well; it is not bad for coatings.

    Craig, using pure undiluted Isopropyl to clean lenses 2 to 3 times a day will wear down coating MUCH faster than using only soap and water or a PH balanced lens spray. It is a fact that I have seen with my own eyes.

    It is one thing to clean a lens with isopropyl prior to hard coating, or to wipe a lens down prior to affixing a lens tape for edging, but it is a totally different thing to say clients can just go at it with isopropyl and it will have no effects on coatings.


    Check out my thread on this subject, Alcohol is getting ruled out I think do to the punishment I am putting these coatings through, but opinions still seem to very. /shrug just sayin

    My mom roasted a set pulling a pizza out of the oven though, I think heat as most said and lens flex are the main culprits.
    Last edited by Outkast; 08-19-2014 at 04:44 PM.

  4. #29
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    I found this older thread while researching different lens cleaners. In my experience, most of the time crazing on a new pair of glasses is due to the combination of heat and stress during frame adjustment, especially with a dramatic zyl adjustment. Try popping your lenses out, adjust frame with demo lenses in, then re-insert the Rx.

  5. #30
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    I'll take that bet...

    Quote Originally Posted by ml43 View Post
    but I bet if I didn't tell you the difference, you wouldn't be able to tell the difference between a crizal AR and a brand A AR.
    Dot the lens with a Sharpie and it will bead on the better (Avance) coatings. Never found that true on cheaper ones. Now if we're talking about Crizal Zeiss SET etc. I don't see a big difference either.
    Last edited by Uncle Fester; 10-30-2014 at 12:14 PM. Reason: clarify...

  6. #31
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    There is much silliness in this thread! Wish we still had the popcorn imoticon. :)

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    Quote Originally Posted by sharpstick777 View Post
    If the lens has an oliophobic top coat, crazing is far more often due to internal issues with the hard coat, and much less with chemical exposure, as the chemicals must enter through the top coat.

    The exception is around the edges, if crazing is only or more around the edge then its more likely a chemical exposure or a lens edged oversize. This can happen with spin coats not laying out evenly as well.

    If its in the center only, its often caused by the lens being surfaced too thin. Lenses have to a certain thickness for good heat dissipation in degassing. (degassing is baking a lens to get rid of water content). This can be exaggerated by blocking, when the lens goes under pressure in the edger it weakens the HC if the material is too thin. An edger with too much chuck pressure can also contribute, but that is rare in a lab, more common in practices that edge though.

    If its across the whole lens, heat/cold or a poor coating is the likely culprit.

    Some lenses also require a primer coat, and if that is skipped it can lead to crazing.

    Often lenses are not crazed when the leave the lab, but the defect shows up a day, a month or a year later.

    +1

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    Hi All,
    Want to know what causes the Crazing of the hih index lenses specially 1.67? What manufactuing defect in AR can cause the problem? Is it dependent on the layer thickness of the entir stack or single layers like SIO2 ,Zro2 or is it the parameters of etching like anode current,anode voltage,neutralizing current etc?

  9. #34
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    Quote Originally Posted by smitan View Post
    Hi All,
    Want to know what causes the Crazing of the hih index lenses specially 1.67? What manufactuing defect in AR can cause the problem? Is it dependent on the layer thickness of the entir stack or single layers like SIO2 ,Zro2 or is it the parameters of etching like anode current,anode voltage,neutralizing current etc?
    167 is prone to expansion/contraction, so heat is the primary cause of crazing. Secondary cause is block mismatch @ bench, causing internal crazing at the edger.
    I bend light. That is what I do.

  10. #35
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    Quote Originally Posted by lensmanmd View Post
    167 is prone to expansion/contraction, so heat is the primary cause of crazing. Secondary cause is block mismatch @ bench, causing internal crazing at the edger.
    Can you please suggest how to proceed with it as our customers complain about crazing in 1.6 index and 1.67 as well.Can we adjust something in the AR stack ?

  11. #36
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    I need to ask. Is the crazing occurring in coater? Plus or minus?
    I would suspect not, as it would be noticeable at AR inspection, or at first inspection. More likely a bench issue, esp., since you mention 1.6, which is more stable.
    Then this. If it is a bench/edging issue, it should be caught @ final.
    This leads me to believe that it is happening at dispensing, when the optician is fitting the frame.
    Last edited by lensmanmd; 09-13-2021 at 09:56 PM.
    I bend light. That is what I do.

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    If this is a Thai sun then this might be the problem.

    My understanding is at about 130 degrees Fahrenheit (54.4 C) crazing can occur.

    I've had someone who left them in a roof auto compartment for glasses in very hot weather produce crazing.

  13. #38
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    Quote Originally Posted by lensmanmd View Post
    I need to ask. Is the crazing occurring in coater? Plus or minus?
    I would suspect not, as it would be noticeable at AR inspection, or at first inspection. More likely a bench issue, esp., since you mention 1.6, which is more stable.
    Then this. If it is a bench/edging issue, it should be caught @ final.
    This leads me to believe that it is happening at dispensing, when the optician is fitting the frame.
    Thankyou for replying. No this is not occuring at the coater. The complains are coming from the customer after 1 monh of use...

  14. #39
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    once upon a time The Vision Council AR Committee created a poster of most common AR failures, six to eight captioned photos. It was very helpful to trouble shoot. I recall every member of VC and OLA received hard copies and it was also downloadable. Supposedly, anything on the internet cannot be lost :).

    best regards and stay healthy!
    Jim Schafer
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