Agfa Chemfree plate

[padrao]

Hello. I have one question regarding this plate, after doing the linearization on plate/RIP, i get the correct values 5% =5% 50%=50% . . . .

But after a print lengh of 100, 200 sheets if i measure the 50%=45%, and remains on that for ever.

what could cause this change, if i measure 50 % after washing , why on the press i get 45 %.

This is creating some problems with print quality, because on the paper i get 52%, witch leads to a low contrast on final job .

The solution i get was to cheat on rip side, to put more 5%, on 50%. After this i get 55% on plate , and the print result is ok .
If i take this plates from the press machine i measure with plate densitomiter 50 %.

This can be because this is a negative plate ? Because with positive plates i never had any problem .

I am asking if any one had measured one plate, after print one job ?

see attached PDF to make it easyer to understand .

 

[KevinC@EFI]

Hello. I have one question regarding this plate, after doing the linearization on plate/RIP, i get the correct values 5% =5% 50%=50% . . . .

But after a print lengh of 100, 200 sheets if i measure the 50%=45%, and remains on that for ever.

what could cause this change, if i measure 50 % after washing , why on the press i get 45 %.

This is creating some problems with print quality, because on the paper i get 52%, witch leads to a low contrast on final job .

The solution i get was to cheat on rip side, to put more 5%, on 50%. After this i get 55% on plate , and the print result is ok .
If i take this plates from the press machine i measure with plate densitomiter 50 %.

This can be because this is a negative plate ? Because with positive plates i never had any problem .

I am asking if any one had measured one plate, after print one job ?

see attached PDF to make it easyer to understand .

Generally, that's called "sharpening" on press - where the dots wear down to something smaller over the course of a print run. In your case it's happening quite quickly.

It could be a plate quality issue, it could be that your press chemistry is attacking the plate, or it could simply be that the plate is under-exposed in your CTP (if you under-expose Azura, the top layer is fused, but underneath it's still soluable - leading to attack from the edges of the dots).

Generally with negative plates, the more you expose them, the more durable they become (to a point). I'd start there - but it'll throw out your linearization too, so be careful. If that doesn't help, call Agfa for support.

(I can't believe I just gave advice on fixing a competitor's plates... )

 

[DCurry]

When we switched to the Azura TS a year ago, the plate tech said that when measuring the plate, you want to vigorously rub the area with a damp cheesecloth in order to wash the gum off so the gum doesn't taint the reading.

He also said that the dots would sharpen up 2-3% on press during makeready, so we aimed 3% high on plate knowing this would happen.

 

[KevinC@EFI]

When we switched to the Azura TS a year ago, the plate tech said that when measuring the plate, you want to vigorously rub the area with a damp cheesecloth in order to wash the gum off so the gum doesn't taint the reading.

He also said that the dots would sharpen up 2-3% on press during makeready, so we aimed 3% high on plate knowing this would happen.

If your dot reading doesn't match the result on press, what's the value of reading it in the first place? Why wouldn't you just read the dot on press (after the first hundred wasted sheets... yuck!) and get an accurate measurement of the result?

Wait - that's exactly what we do with Thermal Direct - minus that much waste paper.

(and all that from a company who tries to make a big deal about being able to read the dots on the plate... when that's apparantly not so useful with Azura either!)

Kevin.

 

[DCurry]

If your dot reading doesn't match the result on press, what's the value of reading it in the first place? Why wouldn't you just read the dot on press (after the first hundred wasted sheets... yuck!) and get an accurate measurement of the result?

Because of dot gain.

You'll never convince me that being able to actually see my image on the plate before sending it to the pressroom is a bad thing. Who wants to wait till the plate washes up on press to find out if there is a problem?

 

[gordo]

Posted by Kevin@Kodak
If your dot reading doesn't match the result on press, what's the value of reading it in the first place?

Because of dot gain.

IMHO that's not correct. You can deal with dot gain without measuring what's on the plate. In fact, that's how dot gain compensation curves are typically created. You just need the requested tone value in the file and the measured tone value in the presswork.

You might measure what's on the plate in order to certify the consistency of plate imaging - but anecdotally, people on this forum as well as Agfa representatives say that the :Azura plates are consistent so there's no real need to measure them.

Or as Steve Musselman of Agfa will write:

Padrao: You'll find that given proper exposure, set that once, and forget measuring plates.

best, gordo

 

[SteveAgfa]

Padrao:

Like many negative plates, Azura can use a slight curve in the mid-tones.

Once your plate technicial rep. has established optimum exposure, don't play
with the exposure, as Azura doesn't respond to exposure tweaking, since
it has an extremely wide exposure latitude.

You'll find that given proper exposure, set that once, and forget measuring plates.

Regards,

 

[VladCanada]

<<You'll find that given proper exposure, set that once, and forget measuring plates.>>
... and dont do any PM for your CTP!?

 

[padrao]

Hi Agree with Gordo . The linearization is very important for me .
Because if i measure de dot gain on press, a new variable or several are introduced .
I mean the paper, ink, blanket . . .
The other PCM, ISO12647, is a diferent job,where most of customers have to paid for that service .

I have to leave the customer with correct calibration on CTP,means focus and laser power .
And on costumer´s with ISO implemented, the linearization is important, because if he change the plate brand, just make the correct linearization, and the dot gain curves can remain the same .
A lot of time,money and wasted paper can be saved .
I never had measured one plate after printer job finish. There are customer´s with Image control, Axis Control and so far i never saw this problems .
But it was a interested topic for me, because lot i had learned i have to think everything again .

All the Best
Padrao

 

[gordo]

And on costumer´s with ISO implemented, the linearization is important, because if he change the plate brand, just make the correct linearization, and the dot gain curves can remain the same .
A lot of time,money and wasted paper can be saved .

Just to be clear. IMHO, for most printers, there is no value in using a curve to linearize the plate and then use a second curve on top of that to get the tones on press that they want.
Most printers just need a curve to get the tones they want on press - no need to linearize first.
The job of the plate is to be consistent since without that consistency plate curves can't work.
If the printer changes the plate brand, it is simple to build a new curve - there is no wasted paper or press time to do that.

best, gordon p