Azura TS

[Hessel]

This sound like the same problems we have with our Agfa VCF plate on web offset (newspaper). We have 2 presses and the problems occure on the new press. Sometimes after 10.000 copies the image wears the same like TF019 discribes. In what way will the ink container temp affect the TAC of the ink?

[Alois Senefelder]

Gentlemen,

1) The initials TAC stand for Total Area Coverage not the TACK of printing ink.

2) The tack of printing ink will not remove image areas.

3) The Indications point to a press problem.


Regards, Alois

* Mr Roskam, I suggest you read the PDFs I have posted

[Lukas Engqvist]

@Alois Ty for spelling clarification, but I will have to contradict you on that tack can in fact remove image area. Now if it was a combination of tack, and a certain paper type I can't say for sure. But there was one regular job printed on a certain stock that we needed to either print when the machine was warmer (meaning the tack was less as viscosity increases and stickyness decreases with heat) or if we needed to run that job first we needed to swich to more fluid/less tacky ink. Now you may have some scientific reason saying that it was not so… but I have real world experience of that fact.

[RGPW17100]

Your post mention that you have been running the same ink for the last two weeks. Why the new ink. What ink are you running? A change in ink could be your problem

[Alois Senefelder]

Hello Lukas,

Litho Plate Coatings ---

1) The image coatings must be wear resistant, solvent resistant and unaffected by fount solution additives.

Phase Change Coatings --

2) Infrared radiation is used to convert a soluble coating to a insoluble oleophilic image ---
thermal coatings consist of various heat-sensitive resins.

Quote " ......but I have real world experience of that fact" Lukas Engqvist

*** Well, being a Sorcerer's Apprentice for seven decades ---- what can I say !


Regards, Alois


"Remember the tortoise --he only makes progress when he is sticking his neck out"

[TF019]

We have been running Hostmann inks for about 6 months, the batch of inks we have been running for the last two weeks is from the same lot number. I should of clarified this point.

The job in question going back on press tonight as the client made some changes to their file. So all of the work we have done is billable and we are starting from scratch (15% of prior run ends up in the recycle bin). Sometimes even us printers get a break once in a while. Sigh...

If the issue continues to pop up I will continue to post but we have run 6 jobs since changing the C and M units and have not had any problems since.

[Lukas Engqvist]

@Alois, yes in principle I understand your quotes, and I'm sorry if I use a too casual way to express myself.

As I explained there was a situation where a certain ink /paper /temperature caused abnormal wear on plate. Now if it was the fount solution or the fount solution reacted with somthing in the coating I cannot say. I heard the discussion going on about the grind of the pigment in the ink also being a possible culprit (it could be more than just the tack in the ink differing or the tack/viscosity giving abrasive quality… but here we are getting into hairsplitting semantics where what I was trying to express was that there was something going on in the shadowlands between chemistry and physics on the press). Since either changing the stock, the ink to a less sticky variant or sheduling the job for when the press was no longer cold, meant that the job would run normally, I do not see how any theory would change that. Now there could on a microcosmic analysis be even more complex issues at stake such as thick sticky ink pulling off coating from this particular paper stock causing it to guild up on the blankets which would then have an abrasive quality on the plate... I did not go into the molecular levels (I neither have the knowhow or apparatus) But the NET effect was that any of thethree variables: a low tack ink, higher temperature press or different stock made the necessary difference.

I do understand that a Litho plate should not react to press chemicals, and that they are rigourously tested. But there will be extreme circumstanses, and in those cases it is importat not to hold fast to what SHOULD be but to consider what MIGHT be, so that you can try the different possible scenarios till you find where the problem lies.

(I find it curious that just switching magenta and cyan printing order should circumvent the problem. What has changed between the units...*the paper is a little more damp, and there is possibly a thin ink film of magenta on which the cyan is printed on, which means the paper will not stick as hard to the blanket, which in turn means less chance of build up of paper particles on the blanket... which means less risk that there will be anything abrasive on the plate image areas... but true this is just speculation...)

Hope TF019 gets the job through

[FujiFrank]

I would suggest that it is the lack of water pickup in the ink that is causing the wear. Even though you are not changing ink, your ink is changing around you. If you test the same ink in a medium tack, you may see different results.

Ink that is NOT taking up water is not properly emulsified. If it is not emulsified then it has a more coarse nature and will wear on the plates in these Komori presses I believe.

Best of luck,