Black spots/dots on Mdag

[simonechoulle]

Hi All

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

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[photolytic]

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.

[simonechoulle]

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

[photolytic]

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

[simonechoulle]

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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[simonechoulle]

the ” collection ” :

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[simonechoulle]

Some more …et voilá !

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[simonechoulle]

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

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