Inking of non printing areas on ctp plates on start

[alekbelia]

Hi
we are ctp bureau. Time to time some our clients send us prints on attached photos. It's happen immediately after printing start. After cleaning with plate cleaner, problem solved.
We are producing plates for many printers. Some clients are happy when somebody reports such problem. Everything in both processors is checked so many times.

 

[Cornishpastythighs]

Is the issue only with one printer as you say you produce plates for many customers.

 

[Magnus59]

As a bureau you don't have control over the printing conditions. Using the correct fountain solution is important, you need to talk to these customers about chemistry on the press to ensure it is compatible with your plates.

 

[alekbelia]

As a bureau you don't have control over the printing conditions. Using the correct fountain solution is important, you need to talk to these customers about chemistry on the press to ensure it is compatible with your plates.

We are working with over 20 small to medium printing plants. Most of the time all customers are happy with our plates. Only few days in 3-6 months some customer start to report about this problem. We are using Agfa gum and not changing type of plates (mostly very good but chinese or taiwan plates) for years per customer. We have no any other problems with customers - only time to time small or huge areas of non inking parts of the plate are taking ink when print start. After cleaning by hand the plate on the machine with cleaning solution everything is going fine. In the same time other printers or other machines in the same printer house do not have any problems.
We have 3 ctp-s and 2 processors. There is no signs that problematic plates are produced from some processor or ctp.
My question can be refined: Is there a role of alcohol or other additives in fountain solution in process of inking non printing areas of the plate?
Big thanks for answers!

 

[joyce]

I have seen this problem before with Agfa no chem plates. It did not appear until October of 2017. The plate processor speed was set at 50cm per minute We slowed the speed to 38cm per minute. The problem has never appeared again.

The plates were manufactured in 2 different facilities. France and the USA. We started to see the difference with the plates made in France

 

[Alois Senefelder]

Hello alekbelia,


What you are seeing is - Oxidation Scum Marks, why I say this --- problem solved when cleaned with Plate Cleaner.

Salient Points : 1) ARE you 100% sure that the plates are "Gummed Up" correctly ?


2) What is the time span between you making the plates and customer's time on Press ??


3) Have ALL your customers "Check the F/S Chemistry," !!


4) If possible have some one go and see "Press Start -up" procedure.



Regards, Alois

 

[Alois Senefelder]

Hello alekbelia,



I suggest you read many of my "Posts" regarding the use IPA in Fountain Solutions.


Regards, Alois

 

[alekbelia]

Hello alekbelia,


1) ARE you 100% sure that the plates are "Gummed Up" correctly ?
2) What is the time span between you making the plates and customer's time on Press ??
3) Have ALL your customers "Check the F/S Chemistry," !!
4) If possible have some one go and see "Press Start -up" procedure.

Regards, Alois

Hi, Alois,
1. Yes, plates are gummed. Gumming section is checked every morning.
2. Time between making plates and press is between 1 and 5 days.
3. After all I will try to read all about F/S chemistry, because I start to understand that when problem occur in the press, first what pressman think is that plates are bad. My only argument is that on other presses there is no problemя at the same time.
4. Photos are from Heidelberg SM52. Startup procedure on press is like every day for years.

I have a question about IPA - isopropanol? Is it possible lack or excessive quantity of IPA to make this kind of marks?

 

[Alois Senefelder]

Hello alekbelia,


You make - 3 consecutive sets of 4 colour plates for 3 different customers and only 1 customer complains, you need to know what is going wrong!


IPA enriched F/S causes no - Scum/Toning or Oxidation Marks. Again read my Posts.


Question: Whose Plates are you using ?



Regards, Alois

 

[majklcze]

Hi,

We have exactly same problem right now!

1) I dont think it is oxidation, because oxidation looks differently imho, it should be small points. I thinked this too, but our plate gum is 100% ok.

2) I have seen the change, when I was labouring with plate gum dilution (1:3 with destilled water right now), but in fact, this should be pointing to another problem, not the problem of the gum - ad 3

3) When I´m writing theese lines, I think its problem with Stabilizer concetrations! (maybe IPA also, but Stabilizer mainly) I think when we add more water to gum, it is easier for press to swim out the gum from plate. But problem should be caused by Stabilizer dosage.

 

[Alois Senefelder]

Hello majklcze,


Enlightenment! .......................... The Chemistry of Lithographic Plate Surface.


1a) Oxidation Marks, are the result of poor gumming-up procedure, this results in the exposed non-image area

of the Anodizing (Aluminium Oxide) becoming "Sensitized" to printing Ink. Gum Arabic used to "Desensitize" the plates should be 8 degrees Baume and NOT DILUTED.


1b) This problem can also arise at a prolonged press stop, where the plate is oppostite the Dampeners.


2) The conductivity of the F.S. be correct also the pH


3) Use the plate manufactures - Plate Finisher (Undiluted).


Regards, Alois