Lens cleaning - early fungus growth

Discussion in 'Camera Building, Repairs & Modification' started by Fluorsynapse, Oct 16, 2009.

  1. Fluorsynapse

    Fluorsynapse Member

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    I have a question where I know there will be diverse opinions, and even our most experienced lens tech is unsure of the best approach.

    The problem is a Sekor 50mm C lens (multicoated) with peripheral mold hyphae on the outermost glass element, only detected after a private purchase.

    Given the reportedly fragile structure of early multi-coatings, here by Mamiya, what is the best approach for minimizing optical artifacts from current and further mold growth, when some cleaning methods could also damage the lens coatings?
     
  2. Q.G.

    Q.G. Inactive

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    A high dose of UV light will kill it.
     
  3. juan

    juan Subscriber

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    And there's probably enough UV in sunlight. Open up the lens and leave it outside in the sun for a couple of hours.
    juan
     
  4. Fluorsynapse

    Fluorsynapse Member

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    I have already tried long wavelenght uv. The only way to assess its effect is to wait for more mold growth and damage to occur later, both difficult to detect by simple visual inspection until too late to fix.

    More lethal short wave uv does not penetrate glass well, and some edge regions may not even be reached by external uv light sources.

    With either approach there is no way to be sure whether residual mold nuclei survive that will generate more hyphae later, and even the presumably "dead" hyphae can still cause optical artifacts, and possibly etch the lens coating as they decay.

    Together, these considerations argue for a careful cleaning, but what agents can eliminate mold hyphae without damaging the fragile lens coating?
     
  5. Dave Dawson

    Dave Dawson Member

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    In other threads I has seen Listerine mouthwash recommended and also dilute bleach *BUT* I haven't ever needed to remove any fungus so proceed with caution.

    Cheers Dave
     
  6. Q.G.

    Q.G. Inactive

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    Regular, repeated UV exposure should keep the fungus away on the long run too.
    I don't think that the thingy decaying will hurt the glass or coating in any way. It's the fungus' metabolism that produces things that will etch the glass.

    The only way you can be relatively sure that the fungus is killed is using a desinfectant.
    The downside of that is that you can only do that on surfaces you can get at (obviously), and that it involves rubbing, which may do things to the coating.