Results 1 to 9 of 9

Thread: "There was shrinkage!"

  1. #1
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    9,386

    "There was shrinkage!"

    Can someone help me understand this?

    Looooonnnng ago, a pair of previously successfully-glazed CR39 lenses came back into my fledgling office, too loose for the metal frame they once fit perfectly.

    In those days you could call a lab owner, and I asked him what happened to the lenses such that they are now so loose and falling out.

    He said something to the effect of "Aw, dang it, we see that occasionally. I think they didn't cure them right. Put them in hot water and they'll be fine."

    So, I did, it worked, and it didn't need re-done later.


    Over the past glorious 30 years or so of optical bliss, I'll get the odd CR39 job that seems to shrink and fall out. (I'm working on one, as I type.) I pop it into hot-but-not-boiling water for about 5 minutes, and they're good to go.

    What's going on, here?
    Last edited by drk; 01-18-2019 at 01:55 PM.

  2. #2
    Master Jedi King of the Lab's Avatar
    Join Date
    Jul 2012
    Location
    Los Angeles, CA.
    Occupation
    Optical Laboratory Technician
    Posts
    413
    Erik Zuniga, ABOC.

  3. #3
    Master Jedi King of the Lab's Avatar
    Join Date
    Jul 2012
    Location
    Los Angeles, CA.
    Occupation
    Optical Laboratory Technician
    Posts
    413
    I have never heard about this trick, and as far as I have ever trying to explain this to PT's, I have told them in the past that the bevel eventually wears thin (erodes) or that the plastic lens warp after the ripe old age of a few years.
    Erik Zuniga, ABOC.

  4. #4
    Master OptiBoarder optical24/7's Avatar
    Join Date
    May 2006
    Location
    Down on the Farm
    Occupation
    Dispensing Optician
    Posts
    5,809
    drk, your old lab owner was right. Too short of cure times or IPP ratio ( the catalyst for cr39 monomer) are the usual culprits. It's also why you can have varying degrees of tint penetration when tinting lenses resulting in one lens tinting faster or coming out a certain shade different. CR39 is porous, that's why it's tintable. Soaking in water, the material will up-take some of that moisture increasing the lenses mass somewhat. But that's only temporary until it evaporates back out.

    Back in the late 70's and early 80's I was a manager at a wholesaler who also had cr39 casting ability. We made our own molds and everything.

  5. #5
    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

    Quote Originally Posted by drk View Post


    In those days you could call a lab owner, and I asked him what happened to the lenses such that they are now so loose and falling out.

    He said something to the effect of "Aw, dang it, we see that occasionally. I think they didn't cure them right. Put them in hot water and they'll be fine."
    So, I did, it worked, and it didn't need re-done later.


    What's going on, here?




    drk...........................................CR39 is originally injected into glass moulds and then cured by heat.

    So the guy that told you that they were not enough cured, was right, and you performed a so called after cure, maybe you could tell your patients that you have to put them into a "lens stretcher" to get them bigger again.

    Nice but simple solution.

  6. #6
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
    Join Date
    Oct 2016
    Location
    Maryland
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    1,198
    Wet heat. Hot water or nuke em in a dish of water. Works every time for a short term fix.

    I’m with Erik. The “V” wears down over time in metal frames and starts to round. Happens more with shallow bezels and T bezels more often than true V bezels. The Outdoorsman was the worst!

  7. #7
    What's up? drk's Avatar
    Join Date
    Mar 2004
    Location
    Ohio
    Occupation
    Optometrist
    Posts
    9,386
    Once again, I'm impressed with the knowledge base here.

    (Too bad we don't have enough to talk about most of the time.)

  8. #8
    Master OptiBoarder OptiBoard Silver Supporter lensmanmd's Avatar
    Join Date
    Oct 2016
    Location
    Maryland
    Occupation
    Optical Wholesale Lab (other positions)
    Posts
    1,198
    Quote Originally Posted by Chris Ryser View Post
    "lens stretcher"
    Ha! Along with a box of OCs, AR in a can, etc, etc.....

  9. #9
    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 optiBoard is still alive..............long live optiBoard

    Quote Originally Posted by drk View Post

    Once again, I'm impressed with the knowledge base here.

    (Too bad we don't have enough to talk about most of the time.)



    ............................this is the advantage of us older members here on OptiBoard, that have learned the ropes of the trade from the bottom up, practical as well as theoretical, if we were lucky to be able to get through proper schooling.

    Some of us have been hanging around "optiBORD" just about close to forever of its existence, and have fun to participate in our own style, and share some of a lifelong experience.

    Most of the many other forums have disappeared over time on this continent, and left "optiBoard" still as the leading one on the web according to official website rankings.

    These days of the big changes in our trade, through monopolies that are happening to our profession, of retailing eyeglasses to the public, make an actual forum like this one even more important to get the word out, as there are at any time of the day a few hundred lookers listed that search the past records, that were made since "optiBoard" came onto the web. It is actually also a record of optical history over the last 20 years, or even more.

Thread Information

Users Browsing this Thread

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

Similar Threads

  1. Just substitute "eyeglasses" or "OTCs" for "umbrellas"
    By Barry Santini in forum General Optics and Eyecare Discussion Forum
    Replies: 29
    Last Post: 08-28-2011, 01:27 PM
  2. PLEASE VOTE - Who do you think makes the "COOLEST" & "MOST HIP" eyewear ??
    By EyeGlassesGuy in forum General Optics and Eyecare Discussion Forum
    Replies: 3
    Last Post: 05-23-2009, 06:39 AM
  3. Replies: 0
    Last Post: 10-24-2006, 01:12 PM
  4. 24K web "gold" - AUDIO tributes to a man called "Bob"
    By rinselberg in forum Just Conversation
    Replies: 0
    Last Post: 08-05-2006, 04:15 AM

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
  •