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Thread: I need your help with a scratch coating question! PLEASE!!

  1. #1
    OptiBoard Apprentice
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    I need your help with a scratch coating question! PLEASE!!

    Happy New Year everyone!

    I have a question. I have a finishing lab and purchase stock and uncuts from a lab. I am supposed to get all of my lenses hard coated. My lab has sent me some stock lenses (CR39) that the envelope says uncoated. When I questioned them they claim that they dip them themselves.

    Is there any way to actually verify or be able to recognize that these lenses are hard coated? I have never dipped so I am unsure of the process or if you can tell!

    Please and thank you!


  2. #2
    Master OptiBoarder LENNY's Avatar
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    Feel them! They are much sleeker then uncoated! Order one uncoated

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    Lenny has the best answer.........they feel "sleeker". They also will spin at a higher and more sustained RPM on the floor on the base curve side....but that would ruin them. You would also have to use a RPM gun to test them.

    Seriously:
    1) They will also appear shinier than an uncoated uncut and microscopically the fine polishing marks would be absent(use a slit lamp bio-microscope).
    2) They will caliper very slightly thicker than the listed thickness on the envelope.
    3) A "dip/spin coat" will have a meniscus of thicker coating on the outermost edge of the front side of the uncut. To discern this use a fluorescent tube reflected on a radius out from centre of uncut to the edge.
    4) Look for clamp marks on the edge of the lens, or "holder marks" where the coating will be absent.
    5) The wetting angle should be slightly different, so a drop of water will pod into a smaller droplet than a uncoated uncut.
    6) Occasional dust particles can be spotted as inclusions in the surface, and are acceptable only if they will "cut out".


    The above observations are subject to the quality of the coating, and the skill of the operator applying the product.
    Eyes wide open

  4. #4
    Manuf. Lens Surface Treatments
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    Compare a non coated lens with the coated ones by tinting them. The un coated lens will tint twice as fast and twice as dark in the same time. It could also be a non tint able coating which then would act even worse.

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    OptiBoard Professional Mauro.Airoldi's Avatar
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    If you have a deep coat you'll see on the edge three smal protuberance (0.1mm) . it is the deep clamps sign.
    A second test can be the follow: put a water drop on the lens (smal diameters drop)if you have a angle betwen water and lens arround 30°-40°(drop flat) it is CR naked, if is arround 80°-90° it is hard coat. The AR with hydrophobic you'll finf 105°-115°.
    last test is destroy a lens... deep half of the lens in a solution of water and 10% NaOH or KOH, leave for 30 minutes, if you'll see a delaminatin...it is hard coat.
    note: be careful with the basic solutions!!!

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    i have a CR39 hardcoat that will fail all these tests because its absorbative but it blocks UV. if its 95% or more UV and the other tests dont work its probably hc d. most labs stock uncoated lenses for ar amd tint.

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    I am so happy you all are helping me! Ok from what I am understanding I should feel one I know is hard (scratch coated) and one I think it not. The sleeker one will be hard coated. I can also put a drop of water on the concave side and if it stays balled up when I move it, it is hard coated.

    Mauro can you explain this to me more:deep half of the lens in a solution of water and 10% NaOH or KOH, leave for 30 minutes, if you'll see a delaminatin...it is hard coat.

    What is NaOH and KOH?

    Sharpstick I dont mean to sound dense but how can I check the UV transmision? I do not have a machine or tool to do that.

    I just want to make sure I can check these lenses as the lab is saying they dipped them themselves.

    Thanks again!

  8. #8
    OptiBoard Professional Mauro.Airoldi's Avatar
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    Quote Originally Posted by kpshann View Post
    I am so happy you all are helping me! Ok from what I am understanding I should feel one I know is hard (scratch coated) and one I think it not. The sleeker one will be hard coated. I can also put a drop of water on the concave side and if it stays balled up when I move it, it is hard coated.

    Mauro can you explain this to me more:deep half of the lens in a solution of water and 10% NaOH or KOH, leave for 30 minutes, if you'll see a delaminatin...it is hard coat.

    What is NaOH and KOH?

    Sharpstick I dont mean to sound dense but how can I check the UV transmision? I do not have a machine or tool to do that.

    I just want to make sure I can check these lenses as the lab is saying they dipped them themselves.

    Thanks again!
    During the deeping (half lens is to see difference) the SiO2 of the HC is chemical attaked by the basic solution
    NaOH

  9. #9
    OptiBoard Professional Mauro.Airoldi's Avatar
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    NaOH is Sodium Hydroxide KOH is Potassium Hydroxide you can found it pure or like part of industrial soap

  10. #10
    OptiWizard
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    Usually the sides of the lenses will give it away. If you can see a glossy, kinda drippy difference the hard coat is on it. A bit harder with plus lenses.

  11. #11
    Master OptiBoarder optical24/7's Avatar
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    They may be using the "snake oil" dip coat that was around years ago. Have them "1/2" coat a lens. Drag some steel wool across it and see if there is any difference.

  12. #12
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    The half dip is a wonderful idea! When I look at the sides of the lens I see no marks and the sides look cloudy like if I cut a lens. When I do the water drop test the (factory) hard coated lenses I already have keep the drop of water together as I rotate the lens around. Kinda like a water drop moving on a waxed car. On these ones I am not sure about the water drop kinda smears across the lens... like water running down a window.

    Also all of these lenses are completely clear and whiteish while my other ones (different brand, factory hard coated) have a yellow tinge to them. My known hard coated are also slicker like posters above suggested. I am just not sure if a self dip verses facotry dip could cause this. Also, after the water test the known hard coated had no water drops while the unknown had lots of dried water marking.

    At this point they say they are dipped so I need to make all of these arguments! The 1/2 dip might be a good idea!

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