Black spots/dots on Mdag

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This topic contains 7 replies, has 2 voices, and was last updated by  simonechoulle 7 months, 2 weeks ago.

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  • #17644

    simonechoulle
    Participant

    Hi All

    We are having black spots problems with Mdags. Does anyone had this problem once? Thanks a lot.

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    #17647

    photolytic
    Participant

    Caused by residual polish on plates.
    Replace buffing pad material.
    Filter mercury.
    Vacuum plate holders and fuming trays.
    Wipe back of plates with tissue before fumimg.

    #17648

    simonechoulle
    Participant

    Hello John
    Thanks for your answer but all you said was done! We solved the problem increasing the temperature from 60ºC to 80ºC and develop for 4 minutes instead 10 minutes and those very circular spots disappear!
    We only had those spots with Mdag not with Bdag.
    Best!
    Simone

    #17649

    photolytic
    Participant

    Hello Simone
    Unless you also cleaned the walls of your mercury box, it is puzzling why the temp/time change worked so well.
    Perhaps the higher temp allowed refluxing mercury to rinse accumulated polish particles from the walls of the box.
    I develop under vacuum for 2 hours at 20C and get no spots if the plates and box are clean.
    Best,
    John

    #17650

    simonechoulle
    Participant

    Hi all,
    Here is a little “collection” of our various black spots, taken from a bad miscroscope.

    We continue doing tests and reading, changing lots of variables, even plate provider…still we do have some.
    We’ve started the developpement from very cold, for a test, and it did increase huggely the amount of spots.
    We went back to a 85/90 degre developpement…
    from the same plates, a becquerel comes casi perfect.

    We keep you informed when progress are coming !

    Best regards

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    #17652

    simonechoulle
    Participant

    the ” collection ” :

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    #17663

    simonechoulle
    Participant

    Some more …et voilá !

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    #17670

    simonechoulle
    Participant

    Thanks a lot for your help John, as always.
    Merci beaucoup !

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