Page 1 of 2 12 LastLast
Results 1 to 25 of 39

Thread: Why do lenses craze?

  1. #1
    Bad address email on file
    Join Date
    Aug 2010
    Location
    Canada
    Occupation
    Optical Retail
    Posts
    95

    Why do lenses craze?

    Client picked up her glasses three days a go and she came back because one of the lenses were crazed, it was replaced and than she came back again because the other one got crazed when it wasn't before, strange.

    What are the reasons they craze? Bad batch? Should I ask her what she does for a living? I know sometimes if the lens is inserted to tight it can happen but she's definitely doing something to craze them.

    I was thinking of giving her a easy clean coating.

    What do you guys think it can be?

  2. #2
    Master OptiBoarder
    Join Date
    Apr 2012
    Location
    Bangor, ME
    Occupation
    Dispensing Optician
    Posts
    678
    whats she cleaning them with? i had a guy who cleaned his with alcohol every day and that happened.
    "what i need is a strong drink and a peer group." ... Douglas Adams - Hitchikers Guide to the Galaxy

  3. #3
    Master OptiBoarder
    Join Date
    Jun 2013
    Location
    Kankakee IL
    Occupation
    Dispensing Optician
    Posts
    421
    I clean mine everyday with alcohol. .. :-)

    Heat is usually a factor. The plastic expands and the ar don't ... or I had a high minus in a flexible optyl frame... the center was so thin the lenses easily folded in this particular frame it they kept crazing. We ended up switching frames and was no longer an issue.

  4. #4
    Master OptiBoarder
    Join Date
    Apr 2012
    Location
    Bangor, ME
    Occupation
    Dispensing Optician
    Posts
    678
    Quote Originally Posted by Slim View Post
    I clean mine everyday with alcohol. .. :-)

    Heat is usually a factor. The plastic expands and the ar don't ... or I had a high minus in a flexible optyl frame... the center was so thin the lenses easily folded in this particular frame it they kept crazing. We ended up switching frames and was no longer an issue.
    Click image for larger version. 

Name:	shame.JPG 
Views:	90 
Size:	30.1 KB 
ID:	11162
    "what i need is a strong drink and a peer group." ... Douglas Adams - Hitchikers Guide to the Galaxy

  5. #5
    ABOM Wes's Avatar
    Join Date
    Nov 2007
    Location
    Earth
    Occupation
    Optical Laboratory Technician
    Posts
    3,194
    What does the crazing look like? Is it everywhere or centrally located and shaped like a block? Are the cracks vertical, horizontal, circular, or sporadic? What's the shape of the frame? What's the RX?
    Wesley S. Scott, MBA, MIS, ABOM, NCLE-AC, LDO - SC & GA

    “As our circle of knowledge expands, so does the circumference of darkness surrounding it.” -Albert Einstein

  6. #6
    Bad address email on file
    Join Date
    Dec 2013
    Location
    Bristol
    Occupation
    Dispensing Optician
    Posts
    268
    Crazing in my experience is down to heat. The best way to craze a lens quickly is to pop it into a frame heater.

    The best way for a patient to do it could be very hot air (hairdryer - I've seen that before, but it's not common) or they could have been left in direct sunlight in a hot environment. A car is a perfect environment for this, as it works like a greenhouse almost.

    Ask her - what have you got to lose? You've already wasted two pairs of lenses, what if you have to do this every week for six months??

  7. #7
    Master OptiBoarder
    Join Date
    Feb 2013
    Location
    PA
    Occupation
    Dispensing Optician
    Posts
    1,607
    I had a patient with crazed lenses. I told her it looked to me like she was cleaning it with chemicals (such as windex). She told me I was crazy... she only uses the lens cleaner we sell...except when she uses her husband's denture cleaner on them. Uh what?

  8. #8
    OptiBoard Professional nicksims's Avatar
    Join Date
    Sep 2011
    Location
    Denver
    Occupation
    Optical Laboratory Technician
    Posts
    176
    As far as heat goes, sometimes a good blast from an oven door just opened (although rare). Steam room or Sauna also is a possibility. Wes has a good question- if the crazing is just in the center of the lenses, it could have been from edging or a strong thumb pushing on the lens to mount. Is the crazing more of the thin lines (like a spider web) or more of a wavy smudging throughout the lens? And if the lenses are too tight, that will make the lenses more susceptible and likely to craze. And cleaning them with alcohol for only a couple of days shouldn't have caused this. Unless the a/r was bad to begin with.

  9. #9
    OptiBoard Professional
    Join Date
    Sep 2011
    Location
    Ill
    Occupation
    Optical Retail
    Posts
    121
    denture cleaner on them that a new one

  10. #10
    OptiBoardaholic other_bill_fea's Avatar
    Join Date
    Aug 2012
    Location
    Morton, PA
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    247
    Temperature will cause the lens coating to expand and contract. If the hard coat on the lens is uneven (as is often the case with back-side spin coating), it will expand unevenly. The uneven expansion under the AR stresses the AR coating, and causes it to crack/craze.


    This is why 'high end' AR coatings use a dip coat. The dip coat can be controlled and applied much more evenly than a spin coat, and they tend to have fewer problems with cracking and crazing.


    Since a spin coat thickness can vary from one lens to another, this could be why one lens would craze and one would be fine.


    Did she maybe just leave them on the dashboard of her car?
    FEA Industries
    Independent Wholesale Optical Lab
    www.feaind.com
    www.optmagazine.com
    Morton, PA

  11. #11
    OptiBoard Novice
    Join Date
    Jun 2014
    Location
    Northern AZ
    Occupation
    Dispensing Optician
    Posts
    3
    +1!

  12. #12
    Manuf. Lens Surface Treatments
    Join Date
    Aug 2002
    Location
    in Naples FL for the Winter months
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    23,240

    Blue Jumper What does the crazing look like? ................................

    Quote Originally Posted by Wes View Post

    What does the crazing look like? Is it everywhere or centrally located and shaped like a block? Are the cracks vertical, horizontal, circular, or sporadic? What's the shape of the frame? What's the RX?

    Wes has given you the proper answer. Without knowing how the crazing looks like how can you get proper answer to you question.

    You will only get a guessing game.

  13. #13
    OptiBoard Apprentice OptiBoard Silver Supporter
    Join Date
    Feb 2006
    Location
    Sacramento, CA
    Occupation
    Lens Manufacturer
    Posts
    22

    Chemical, heat, compatible AR

    AR may craze due to:
    Exposure to heat
    Exposed to acetone based products
    AR coat incompatible with lens material (especially high index)

    • aBBerated

  14. #14
    Master OptiBoarder
    Join Date
    Jun 2008
    Location
    Seattle WA
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    3,137
    Crazing can also happen because of a contaminated coating, too much water in the air line, the coating is old or other errors.

    A great hard coat is not necessarily the hardest, but one that expands at the exact same rate as the base material. The harder the coating the great its possibility of crazing.

  15. #15
    Master OptiBoarder
    Join Date
    Jun 2008
    Location
    Seattle WA
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    3,137
    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.
    Last edited by sharpstick777; 07-29-2014 at 11:27 AM.

  16. #16
    Rising Star OptiBoard Silver Supporter
    Join Date
    Jun 2012
    Location
    St Louis
    Occupation
    Dispensing Optician
    Posts
    78
    Heat is the problem, almost always! Hot water from the faucet has crazed a few lenses lately. I figured that out by grilling a customer who wears their glasses all the time. Have the been left in the car? no. Checked in luggage? no. Wore them in a sauna? No. Any reason at all you can think they would have got hot? Well hmmmmm. I do clean them every day under hot water. What? I let the water get as hot as possible and then clean them. Yeah don't do that anymore. Cool water. Never hot. I even had a guy boil his glasses thinking that would help clean them.... Face palm

  17. #17
    Bad address email on file
    Join Date
    Dec 2006
    Location
    Florida
    Occupation
    Dispensing Optician
    Posts
    2,175
    Quote Originally Posted by becc971 View Post
    whats she cleaning them with? i had a guy who cleaned his with alcohol every day and that happened.
    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.

  18. #18
    Bad address email on file
    Join Date
    Dec 2006
    Location
    Florida
    Occupation
    Dispensing Optician
    Posts
    2,175
    Quote Originally Posted by globaljp View Post
    Heat is the problem, almost always! Hot water from the faucet has crazed a few lenses lately. I figured that out by grilling a customer who wears their glasses all the time. Have the been left in the car? no. Checked in luggage? no. Wore them in a sauna? No. Any reason at all you can think they would have got hot? Well hmmmmm. I do clean them every day under hot water. What? I let the water get as hot as possible and then clean them. Yeah don't do that anymore. Cool water. Never hot. I even had a guy boil his glasses thinking that would help clean them.... Face palm
    Crazing after a lens is older than a month is almost always a heat issue. We get them in Florida and I did it myself to a pair but we find the most problems with transitions; it is not even close.
    We replace at 1/2 off after one year but before year two and at n/c in first year one time.

  19. #19
    Bad address email on file
    Join Date
    Aug 2010
    Location
    Canada
    Occupation
    Optical Retail
    Posts
    95
    Thank you for all the responses.

    It's a slightly curved frame and she's not doing anything extraordinary with it in terms of cleaning or leaving it exposed in the sun, crazing seems to be in the middle. I have her a easy clean lens, let's see if that fixes the issue.

  20. #20
    Master OptiBoarder OptiBoard Gold Supporter
    Join Date
    Mar 2012
    Location
    Maryland
    Occupation
    Dispensing Optician
    Posts
    2,103
    Quote Originally Posted by Craig View Post
    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.

  21. #21
    Master OptiBoarder OptiBoard Gold Supporter
    Join Date
    Mar 2012
    Location
    Maryland
    Occupation
    Dispensing Optician
    Posts
    2,103
    Quote Originally Posted by Mrmessi View Post
    Thank you for all the responses.

    It's a slightly curved frame and she's not doing anything extraordinary with it in terms of cleaning or leaving it exposed in the sun, crazing seems to be in the middle. I have her a easy clean lens, let's see if that fixes the issue.
    Is it a "slightly curved frame" and the lenses are aspheric with a thin center thickness? Jamming very flat lenses into a curved zyl frame will bend them, and over time will craze many of them - especially if the lens was edged with a long A measurement. Best to go spherical or Free form SV here for mounting purposes.

  22. #22
    OptiWizard
    Join Date
    Apr 2014
    Location
    California
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    382
    Quote Originally Posted by Tallboy View Post
    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.
    pure IPA should not affect the coating itself, but it will have an effect on the hydrophobic/oleophobic layer

  23. #23
    Bad address email on file
    Join Date
    Dec 2013
    Location
    Bristol
    Occupation
    Dispensing Optician
    Posts
    268
    Quote Originally Posted by ml43 View Post
    hydrophobic/oleophobic layer
    That seems like an important part of the coating, really.

  24. #24
    OptiWizard
    Join Date
    Apr 2014
    Location
    California
    Occupation
    Other Optical Manufacturer or Vendor
    Posts
    382
    Quote Originally Posted by standarduck View Post
    That seems like an important part of the coating, really.
    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.

  25. #25
    Bad address email on file
    Join Date
    Dec 2013
    Location
    Bristol
    Occupation
    Dispensing Optician
    Posts
    268
    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.
    I have so much to learn. Had no idea.

Thread Information

Users Browsing this Thread

There are currently 1 users browsing this thread. (0 members and 1 guests)

Similar Threads

  1. 1-year old Transitions with Crizal starting to craze
    By jkane1979 in forum General Optics and Eyecare Discussion Forum
    Replies: 17
    Last Post: 05-14-2012, 03:48 PM
  2. What is causing a single vision Crizal Avance lens to craze?
    By Happylady in forum General Optics and Eyecare Discussion Forum
    Replies: 20
    Last Post: 10-28-2011, 01:55 PM
  3. Latest stupid teen craze
    By cleyes in forum General Optics and Eyecare Discussion Forum
    Replies: 1
    Last Post: 07-12-2010, 10:15 PM
  4. Why do stock poly avance lenses craze so often?
    By witzoptical in forum General Optics and Eyecare Discussion Forum
    Replies: 12
    Last Post: 12-23-2009, 10:14 AM
  5. Replies: 0
    Last Post: 05-17-2007, 11:52 PM

Bookmarks

Posting Permissions

  • You may not post new threads
  • You may not post replies
  • You may not post attachments
  • You may not edit your posts
  •