Any method to determine finishing gum condition before printing ?

[Saulius]

Hello,

is there any method to determine the condition of finishing gum before the printing ? The main interest is how well plates are desensitized. We use Kodak Finisher 850S (acidic) and process plates in advance for 1-2 days, 260-300 square meters per day. It is very not comforting to hear suddenly in a morning from pressroom about huge of paper waste in the night shift.
What signs or measurements would show about bad the current finisher gum condition ?

Thanks in advance,
Saulius

 

[Alois Senefelder]

Hello Saulius,


The answer.......... is yes. Buy a Hydrometer with the S.G. Range - 1.000 - 1.200

Gums and Finishers are aqueous based and do not become exhausted in the same way as Plate Developer.


Regards, Alois

 

[Saulius]

Thank you, Alois, for the suggestion.
As I understand with the hydrometer I can determine if gum is not diluted with water too much during auto cleaning cycles in the processor or at any other circumstances. But if the problem is in gum contamination ? We noticed that it get much darker after very day we have replaced it. We've checked the processor for properly rinsing of plates, if they enter dry enough to the gum section. Have replaced the gum roller from hard to soft, also have replaced the finisher pump to the recommended by Glunz&Jensen.
Currently for the sake of warranty we started replace the finisher every morning with half of 10 l container and we don't dilute it with the water. All printers of three web presses shows thumb up during the month as we started such regime. But we cannot precisely determine when the finisher going to be not effective.

 

[Alois Senefelder]

Saulious,

I'm failing to understand why you are having a problem with Plate Finishers. Stored correctly they are stable, long life chemicals.


Regards, Alois

 

[Throne]

You may be able to measure th ph. The plate developer has a very high ph,water rinse and "finisher" lowers the ph of the surface gum to an acceptable level to use on press. When the ph buffers in the finisher get tired the ph of the finisher rises.

 

[Saulius]

It is better one time to see than many times to hear (to write in my case).
The scumming occurs with plates processed on processor which at least changed pH from the fresh gum, but the color and flowing particles say about the contamination.

 

[Alois Senefelder]

Throne,


You have a poor understanding of the "Chemistry of Lithography "


Regards, Alois

 

[Saulius]

Alois, yes, I agree with you absolutely.
And agree that measuring pH and conductivity of gum looks wild, but I guess nobody will arrest me if I will try to measure it, just for fun. Maybe I will be the first in the world.
You have stated, that gum "stored correctly they are stable, long life chemicals". Gum stored on the shelf is perfect to us too, but the problem is that we use it.

Regards,
Saulius

 

[Saulius]

just in case,
the acetone test of the developed plates showed no difference between two processors. Emulsion circles is hard seen.
Both processors use tap water for rinsing and systems are open to drain.
Both finisher systems are in absolute primitive closed loop.
Rinsing water streams on the problematic processor is even stronger than on other processor. The leak of rinsing water to gum section is checked.
The roll of gum is clean as new. There is no bluish residues on it.
The problematic processor was cleaned fully and developer was changed two weeks ago.
Both systems use same chemistry and same plates - Kodak Electra XD.

 

[aqazi81]

It is better one time to see than many times to hear (to write in my case).
The scumming occurs with plates processed on processor which at least changed pH from the fresh gum, but the color and flowing particles say about the contamination.

There must be something wrong with your Glunz and Jensen Processor, We have installed two processors but the gum color is similar to your Kodak processor after days of use.