Blanket scumming

[Cdel]

Hi all, has anyone ever seen this happen. About one quarter of the blanket gets this heavy glaze and streaks. Rest of blanket is clean. Shows up as a dry up on sheet. The plate is clean and has a nice scum line. Thanks for any suggestions. Hopefully the pics show up ok

 

[Beguin]

Hi sir, please change the blanket!

 

[Cdel]

We have done that already many times. Tried different blankets, just keep happening. I cant figure out why it only happens on the Near side.

 

[mantman]

Have you checked roller stripes? -ink and dampening-
Roller bearings?
Ink form rollers oscillate or not?

 

[Cdel]

yes we have checked stripes. clean bearers once a week, we just integrated the bridge roller. That might have helped. I'll give it another day to make sure

 

[Jack liston]

Check for a build up of dry ink between the water pan and matte chrome on water unit

 

[Adil]

Hi sir
With my experience it cn be one of those causes
Too high ink tack
Ink is absorbed too quickly
Too much wetting (over-emulsification)
Unfavorable wetting values
Poor substrate quality (paper coating)

 

[Adil]

I suggest you to Reduce ink tack
Slower ink absorption
Reduce wetting
Improve wetting values (pH, IPA, hardness)
Better media quality (paper coating)
Good luck and let me know

 

[Adil]

Tell me if you have a thermoregulation system on the printing unit ??

 

[Raf77]

What machine is it? How many units? If more than one, is this happening on all units , or just this one? What plates do you use? Process/processless?

 

[Koenig]

Hello there,
For any scumming problem on any printing machine, the basic phenominon is same. The application of dampening solution on the PLATE is to Repelling Ink from Non-Image Areas. The dampening solution forms a thin layer of water on the non-image (blank) areas of the printing plate. Since the printing plate is designed to be hydrophilic (water-attracting) in non-image areas and oleophilic (ink-attracting) in image areas, the water layer prevents ink from adhering to these non-image areas.

• If the (chemistry) foutain solution (Isopropyl Alcohol (IPA) or Alcohol Substitutes) is Good, its temperature is Good, the PH value is Good, and the circulation is also good - Check the machine rollers and its speed
  
• Then check the marked rollers which apply solution to the Prining Plate. if the dampening solution transfered to the plate is too less, scum appears.
• IF the roller adjustment is bad - Scum appears
• IF the Roller diameter is changed (it has a life), the the water transer is improper - Scum appears
• If the Dampening Roller (motor) Speed is not synchronized with machine- Scum apperas
• Look at the below picture to see, how a thin layer of water is applied on the plate.

 

[Cdel]

Thank you everyone. I will try to check all suggestions and give a response. appreciate you all.