Magenta plate going blind

[brenfrit]

Hi can any member be able to shed some light or have experienced this intermittent problem Our issue is on a Geoman and Uniset cold set presses using coldset inks On start up with new plates we run up to+-200000 copies however we we stop for a edition change only black plates on start up the magenta plate fails to clean up to add to this the plate will clean up but jn some areas the ink will not transfer it looks like the plate has gone blind make new set and back to normal it has happened as well on the Cyan And Black there are 6 other printing sites same presses same ink same fount and plates and paper any suggestions
thanks Bren

 

[Cornishpastythighs]

So the 6 other sites are not experiencing the problems you are seeing and are they using plates from the same processor? Have your CTP and processor checked out by a tech and while you are at it do some checking of your press. Rollers settings, durometer. Dampening, fountain solution mixing system, plate/blanket squeezes etc etc.

 

[gordo]

You might be suffering from the effects of calcium carbonate in the paper. It typically shows up most strongly in the Magenta printer. More info here:

http://the-print-guide.blogspot.ca/2010/12/calcium-carbonate-problem-with-better.html

 

[brenfrit]

Hi I asked the plate room to wash the plate off with water once it had come out of the processor and then to gum up the plate with gum Arabic they had a successful night and we will do the same tonight and look forward to see the results

 

[maxon]

Bren, the plate should come up clean if properly processed. What type of plates do you use ? Rinsing the plate again then gumming may improve the hydrophilic properties of non-image areas but have little to no effect on image.

 

[Alois Senefelder]

Gentlemen,

I'm a great believer in K.I.S.S.

Check the Chemistry of the Plate Processor......... via 1) for developer a Conductitivity Meter 2) the Gum - finisher via a Hydrometer


Regards, Alois