Having issues with lined bifocals and trifocals with A/R in every material other than plastic. Seems like I cant find a good combo for lined bifocals with transitions and non glare. I get a lot of them back with the lenses crazing!! Anybody got any good ideas they would like to share ? Very frustrated!!
What AR are you using? Have you brought this up with your lab? Do you have this issue on other lenses with the same AR?
the most common cause of crazing is with the hard coat and temperature extremes. is the crazing on the backside only? front side? A slit lamp will often tell.
A job should NEVER arrive crazed, and its probably happening during shipping., routed somewhere hot.
You may need to send this job to another lab. Labs don't have a lot of flexibility to alter their HC process, and since this has happened on multiple jobs they have process issue. Let them know that you are having repeated issues, sadly, most labs will only change their process when business leaves. Its not your job to solve what HC model and brand they use, its theirs.
We use the Crizal line of ar and really see almost no issues with crazing on any material.
Correct me if I am wrong but I seem to remember that most flat tops are made using LifeRx photochromics and I believe I've heard of issues resulting in the use of A/R with LifeRx. I feel like I was told this by a lab a few years back. Am I totally off base?
"Strictly speaking, there are no enlightened beings; only enlightened activity." -Shunryu Suzuki
We normally use Crizal products, but the issue is with transitions and A/R and lined bifocals or trifocals and any material other than plastic. If its poly, or trivex or even a high index. The combination of A/R and transitions and material seems to craze. Example : the woman I'm replacing for the 3rd time - 1st job was poly,life RX photochromic and Edura tri tek. 10 months later that crazed. Remade into trivex transitions and endure tritek.7 months later I'm replacing again for crazed coating!! Using same material and A/R because my lab tells me I cant get a Crizal product on any tinted lens whether it be transitions or regular tint.Originally Posted by other_bill_fea
I have put crizal coating in the frame warmer, it takes A LOT of heat to make a crizal coating craze. If you are having crazing issues its probably in the curing process or contaminated coating that it is not adhering to the lens correctly.
It can be from the adjusting you are doing at dispense, sand box or fame warmer, if it's a bad a/r it will craze afterwards.
They are correct that Crizal is not compatible with any FT28 photochromic other than CR-39 Transitions. The problem is the poor AR. I'm sure the customer isn't treating them too well either, because even crappy ARs don't magically craze on their own. Check also lens thickness, if it's too thin is will flex and that can crack the AR too. I do everything I can to steer customers out of FT photochromics because they just won't deliver the Crizal standard of durability. The few customers that really need it I explain to them that my preferred lens does not exist in that combination and they will have to take extra care to prevent scratching/peeling/crazing. Every time I dispense it I fully expect to see it back within the year. What can you do?
That's just in poly, since there are no poly FT Transitions. You can get Transitions FTs in other materials, but you still can't get Crizal (or presumably some other premium ARs either).
Vision-Ease is now offering its own ARC from its Venue lab. They are also starting to move into high index and trivex materials. For those of you who are somewhat anti-Essilor/EyeMed/Luxottica/LensCrafters/Cole and on and on, why not try Poly LifeRx with a coating that is specifically designed for LifeRx?
from the adjusting you are doing at dispense .................................
.................all AR coatings are made with SIO2 (silicon dioxide) which is glass.
Your lens underneath is a plastic material which has a different expansion coefficient under heat than glass. Therefore when heated the plastic material will contract or expand more and faster than the top glass layer and therefor craze. The opposite can happen under extreme cold.
Has nothing to do with good or bad coatings, only with the laws of physics.
Last edited by Chris Ryser; 09-25-2013 at 12:29 PM.
But some ARs are far more prone to it than others. As has been said, Crizal is more resistant to heat crazing than anything else I've seen. Some cheap ARs craze when I breathe on them too hard. I'm sure this does have to do with the TD2 undercoating that provides a better substrate, and absorbs some of the expansion/contraction and flexing, which many other ARs don't have. Most cheaper or "house" ARs don't do any base hardcoating, they just drop the AR stack right on the factory SRC, which may or may not play well with the AR.
Deblocking is key. Any AR coated lens I always use the correct deblocking tool. You want to twist the block off, not break it off any which way. Any bending with AR coating is bad. And of course if you are edging in house and your edger has an AR mode use that too.
Same patient... three times... make sure there is not something chemical going on here. Is the patient cleaning their glasses with Windex, or using hairspray, or do they have any hobbies that produce fumes? I agree that at many labs your coating choices are limited and the cruddier coatings are more susceptible to these factors. You can get one of Hoya's better AR coatings on their FT-28's with Transitions.
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