Why does this lens craze so much???? I'm trying to make a job OU -4.50 In a thick plastic frame and it crazed every time. Sent it off to the Essilor lab and it came back crazed twice. Customer wants his money back I suggested hoya or nikon.
Can someone shed any light regarding the crazing, much appreciated.
@Mrmessi: What is the C.T. of the lenses, and were they stock or surfaced? IMO AR coated lenses don't craze, people craze AR lenses. No, I am not with the NRA, USA. LOL
Heavy plastic frame...............check adjustment, if temples are tight when putting frame on face you might create some tension on frame which transmits it to lenses which can craze.
What material are you using?
Originally Posted by Mrmessi
Too much heat was applied to the plastic frame to make it pliable enough to insert the lenses. The lenses absobed the heat and there was too much flexing of the lens on insertion which cracked the coating.
That is even a better explanation............and makes sense
Yeah, but we should not be heating or plastic frames today. With the precise cutting of lenses, all plastic frames should be cold mounted.
Perhaps , maybe, but heat destroys AR lenses just as fast as overflexing them. So let's assume that the lenses were cold mounted and then afterwards the frame was bench aligned using heat to adjust the frame and the lenses were already inserted in the frame . Now the heat to the lens destroys it.
It just is not a perfect world.
If the lens was good after edging but crazes after insertion then there are only two possibilities, ... heat and overflexing.
And that brings another question. How long afterward did it craze and what do the craze marks look like. If they look like chuck marks, then there was definitely an edging issue.
Can we request pictures ?
Thank you for the feedback. I spoke to the Essilor lab and they said the higher the index the coating is more prone to craze. They also said as above mentioned it can happen at the point of adjustment due to the heat and flexing of the frame.
They also mentioned that the frame should not be taken into saunas or left in concentrated heat such as inside the car.
....and you believe everything the lab tells you?
I was hoping you would respond with the centre thickness of the lenses in question. If they are a minus lens, as I suspect they are, they are probably too thin for stability. I find that I have to specify centre thicknesses, depending on the frame I am putting the lenses into (for stability). A poster mentioned cold insertion of lenses, and I agree to a point, but you can also over-flex a thin lens, with cold insertion, so sometimes that can created crazing, too. I would tend to blame lens thickness, or lack of, for most of the crazing problem, whether it is in blocking, clamping, edging, insertion, dispensing, adjusting, or consumer exposure to heat related sources.
Same problem with low power stock Orma Transitions Forte' into a metal frame. Customer called in a couple of days later with horizontal crazing, remade and sized down to a small as possible while still staying in the frame. So far so good. Disappointing for a coating of this caliber, will see if it gets warrantied.
Where did you kept the lens and if it was in an appropriate environment then...bad quality.
Did you asked them some advices about some lens that are better, that resist to activity?
Oh, let us know about the solution you found.
Probably not, but "I" did!
Photonic Resources
We also had this happening and then we realized that they were actually supplying us with old Alize stock and passing it off as Forte!!
Ofcourse! How do you think they get rid of their overstock?
Well, now they can unload through F.D.!
I do know that in high volume labs they skimp on AR processes to speed up turn around times and reduce costs. So if the AR should have say 13 layers on it and the process takes 90mins they will go as low as 5 or 6 layer if they can get a dome out in 60mins. Its a shame quality has to suffer
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