Press Dot Gain help please!!!!!

[contrakid]

Thanks, yes we do, we have the latest Fuji plate control strip. Its not a prepress problem.

 

[contrakid]

When did they just randomly decide to change their print sequence???

If you are running to a standard (I'm only familiar with ISO) they cannot be doing that.

"Strange things are done in the land of the midnight sun by the men that toil for gold."

mmmm... Long story, something to do with new spray powder not being great and having to use first unit for dusting! Plus a very large print job we do every 3wks that has 2 blacks, one tone and one black text. Run 1.5 million and black text plate change every 2500 sheets. Think the spray powder was building up really fast compared to old stuff and they print a big job that had loads of black image missing due to the spray powder build up so print minders have been running black tone on 5th until we could get back on previous spray powder!

Nice, and they wonder why they can't match the proofs!

Got them to print in correct order yesterday and print was a perfect match to my ISO coated v2 proof.

 

[Alois Senefelder]

Black

Black

BeauchampT/contrakid



Black (K) can be printed First or Last, I suggest you read "Gordo's " Blog - - -

"Quality in Print"


Regards, Alois

 

[contrakid]

BeauchampT/contrakid



Black (K) can be printed First or Last, I suggest you read "Gordo's " Blog - - -

"Quality in Print"


Regards, Alois

Yes you can print it on the last if you want your pictures to look dull and dirty all the time. If all your standards are set to print black first your never going to match a an ISO coated proof that is based on black printing first.

Black going down on top of the CMY will kill the other colours and make it look dull in the quarter tone and mid tones areas where black is used with any or all of the CMY, black under the other colours will keep everything looking more open. You will not see much difference in the 3 quarter tones and dark shadows and obviously tones not using black.

There will be times when you may have to run black last but this is always a last resort. Possibly to stop marking on a large Black solid etc.

You could get ok results running a high UCR but for best results always black down first unless your a Newspaper!

 

[gordo]

I think this is the posting that Alois was referring to:

Quality In Print: Ink Sequence - 4/C process & beyond - part 3 of 4

best, gordo

 

[contrakid]

OK I know you can print black last we have done it on and off for years but only when last resort. I know some types of printing have to print last. Newsprint etc.

But if you trying to match ISOcoatedV2 / Forgra39 standard your going to get much closer with Black under CMY not on top and i am talking about Litho offset sheet fed printing.

So do you think 100% Yellow onto of 100% Black looks the same as 100% Black on top of 100% Yellow?

 

[gordo]

OK I know you can print black last we have done it on and off for years but only when last resort. I know some types of printing have to print last. Newsprint etc.

But if you trying to match ISOcoatedV2 / Forgra39 standard your going to get much closer with Black under CMY not on top and i am talking about Litho offset sheet fed printing.

So do you think 100% Yellow onto of 100% Black looks the same as 100% Black on top of 100% Yellow?

I don't know who you're directing your comments towards. If it's me then I agree, for sheetfed the sequence is KCMY. For newspapers it can be KCMY or YCMK with YCMK being preferred.

I don't think 100% Yellow on top of 100% Black looks the same as 100% Black on top of 100% Yellow.

It would be interesting to know the OP's press operator's thinking behind switching to K last down. What problem did he think he would solve with that strategy? How did he think changing the ink sequence would solve it?

best, gordon

 

[contrakid]

I don't know who you're directing your comments towards. If it's me then I agree, for sheetfed the sequence is KCMY. For newspapers it can be KCMY or YCMK with YCMK being preferred.

I don't think 100% Yellow on top of 100% Black looks the same as 100% Black on top of 100% Yellow.

It would be interesting to know the OP's press operator's thinking behind switching to K last down. What problem did he think he would solve with that strategy? How did he think changing the ink sequence would solve it?

best, gordon

Sorry getting a bit carried away Gordon.

Just been reading some of you blogs, very interesting reading.

Think they struggle with large black solids marking when on first unit. I don't know why this would be, maybe you can advise me. But although i get on great with all of our Press minders I don't have great confidence in them sometimes.

Unfortunately in the real world these days Press minders are put under great pressure to turn out as much work as fast as possible and still achieve a high level of quality for low production costs. Hence sometimes corners seem to be cut. This is not helped by going from a very long run low quality job in the morning to a very high quality short run job in the afternoon syndrome!

Also we have had some new spray powder cause text to breakup after very short amount of run after blanket being cleaned. So possibly they have been putting black on 5th and using first unit for dusting until we get better spray powder back in!

Would this explain things?

 

[gordo]

Printing is complicated - with a great many variables. That is why standards and process control are so important as well as documentation and an organized method to correct deviation (problems) when results are not what is expected.

Think they struggle with large black solids marking when on first unit. I don't know why this would be, maybe you can advise me. But although i get on great with all of our Press minders I don't have great confidence in them sometimes.

There are many reasons why this would occur. Has this always been a problem? Did it just start with a certain job? What has changed in your process? etc. (standards, process control, documentation, etc.)

Unfortunately in the real world these days Press minders are put under great pressure to turn out as much work as fast as possible and still achieve a high level of quality for low production costs.

This has been my experience since I first started working in printshops in the mid 1960s - and I know from the literature that it was also true from the beginning. To wit: "Hand writing all these Bibles is too slow, expensive (the cost of wine to keep the monks happy is ridiculous), and the quality is all over the place - we can't get two Bibles to look the same! Hey Gutenberg, got any ideas for a faster, cheaper, and better way to churn out these Bibles?"

Hence sometimes corners seem to be cut.

No, this is where standards, process control, documentation, etc. come into play. Cutting corners is the lazy way and doesn't work.

This is not helped by going from a very long run low quality job in the morning to a very high quality short run job in the afternoon syndrome!

No such thing as low or high "quality" jobs. The manufacturing process is the same. The press itself treats all jobs the same - so should the staff. What may change from job to job is the tolerance for variation from the proof. Sounds like an attitude and management problem - not a technical problem.

Also we have had some new spray powder cause text to breakup after very short amount of run after blanket being cleaned. So possibly they have been putting black on 5th and using first unit for dusting until we get better spray powder back in!

Sounds like a rationalization for a lack of standards, process control, documentation, etc. "We didn't have the time to make a sacrifice to the litho-gods before our shift started. That's why we moved black to the last unit."

Would this explain things?

Yes, gordo

 

[BeauchampT]

Well, if they are having problems with their materials, replace the materials, don't change your process. Like you say contrakid, it will never look the same.

Actually, if you have a good relationship with your press minders, why not encourage them to log their problems with detail (samples, blanket pulls, etc) and maybe they can build a clearer case with management (with you backing them up)?? Two departments will have more power than one

 

[Lukas Engqvist]

Yes logging a problem is very important, even if the logs are not saved, it helps to track what actually is wrong.

 

[contrakid]

Printing is complicated - with a great many variables. That is why standards and process control are so important as well as documentation and an organized method to correct deviation (problems) when results are not what is expected.



There are many reasons why this would occur. Has this always been a problem? Did it just start with a certain job? What has changed in your process? etc. (standards, process control, documentation, etc.)



This has been my experience since I first started working in printshops in the mid 1960s - and I know from the literature that it was also true from the beginning. To wit: "Hand writing all these Bibles is too slow, expensive (the cost of wine to keep the monks happy is ridiculous), and the quality is all over the place - we can't get two Bibles to look the same! Hey Gutenberg, got any ideas for a faster, cheaper, and better way to churn out these Bibles?"



No, this is where standards, process control, documentation, etc. come into play. Cutting corners is the lazy way and doesn't work.



No such thing as low or high "quality" jobs. The manufacturing process is the same. The press itself treats all jobs the same - so should the staff. What may change from job to job is the tolerance for variation from the proof. Sounds like an attitude and management problem - not a technical problem.



Sounds like a rationalization for a lack of standards, process control, documentation, etc. "We didn't have the time to make a sacrifice to the litho-gods before our shift started. That's why we moved black to the last unit."



Yes, gordo

agree with all, unfortunately out of my control although i am trying.

cheers for all guys

 

[danremaley]

Send me an email off line and I'll send you a great book (pdf) for reference Color control by Kelvin Tritton from PIRA. [email protected] 412.889.7643

 

[Suyambu Raja]

hi everyone,

what is the CMYK standard value of print contrast?

 

[gordo]

hi everyone,

what is the CMYK standard value of print contrast?

I don't believe there is one since print contrast is not a target but an indicator of ink/water performance.

Published typical reference values are: K 40+ C 35+ M 35+ Y 30+ The plus + means that if you can achieve a higher value that's better.

Print Contrast in film days was an indication of print quality because the values correlate well to the subjective evaluations of print quality, such as “flat” (low print contrast values) versus “jumps off the page” (high print contrast values). Print contrast is often used as a guide for maintaining proper ink/water balance. But in a CtP world you can apply plate curves to have virtually whatever print contrast you want.

 

[danremaley]

print contrast

print contrast

I don't believe there is one since print contrast is not a target but an indicator of ink/water performance.

Published typical reference values are: K 40+ C 35+ M 35+ Y 30+ The plus + means that if you can achieve a higher value that's better.

Print Contrast in film days was an indication of print quality because the values correlate well to the subjective evaluations of print quality, such as “flat” (low print contrast values) versus “jumps off the page” (high print contrast values). Print contrast is often used as a guide for maintaining proper ink/water balance. But in a CtP world you can apply plate curves to have virtually whatever print contrast you want.

GATF described print contrast as a value of 75% screen tint (film/CTP or otherwise) and solid. The late Ken Rizzo (GATF) measured the higher density of magenta in G7 sheets and noted that the print contrast value dropped when the density reached 1.50 (The 1.44 density created the best print contrast number). A lower number represents a poor print condition. Pressroom research is a thing of the past. .

 

[gordo]

GATF described print contrast as a value of 75% screen tint (film/CTP or otherwise) and solid. The late Ken Rizzo (GATF) measured the higher density of magenta in G7 sheets and noted that the print contrast value dropped when the density reached 1.50 (The 1.44 density created the best print contrast number). A lower number represents a poor print condition. Pressroom research is a thing of the past. .

Print contrast values increase as solid ink densities increase...up to a point...and then the values decrease as solid ink densities continue to increase. In the steam powered days it was a way to determine maximum solid ink density (when print contrast was at its max). But with CtP you can just apply a plate curve to restore maximum print contrast as solid ink densities are increased. So print contrast, in that sense, is no longer much of a useful metric.
Pressroom research has been a thing of the past for decades. Even when it was being done - it was often done so poorly as to be next to useless - even when done by GATF.

 

[Deleted member 16349]

Pressroom research has been a thing of the past for decades. Even when it was being done - it was often done so poorly as to be next to useless - even when done by GATF.

This is very true. Basically all the research done on offset presses was not basic research in how the process works but it was only how the processed worked on that particular piece of equipment with specific inks, paper, screen etc. combination. This has resulted in the last 100 years of experience, developing few basic rules in how the process actually works.

Normally in testing a process under lab conditions, it is very important to control the input variables and the conditions in which the test will be done. Without properly controlling input and condition variables, one can not say anything about the rules that govern the process. The purpose is to look for relationships. Relationships that are mathematically defined. Then if one can obtain the rules, then one will know if one can get predictable results in designing new technologies.

Ink is a major input variable but it is not controlled properly now. It should be.

I dare any researcher out there to do a proper test of the process and report the results. But they will probably not take up that dare because they want to think that they are already doing science, which they aren't. They are only doing industrial trial and error experimentation.

 

[cosmo]

so you are saying you got a 34% dot gain from a 32% plate reading and then 66% on the press? Thats huge, i would look at your plate dot reader, sounds like things are way out of whack, you should only get about a 10-15% from there. I doubt its the press, i havent seen any go that bad, and your press is a late model machine which should print very sharp.

 

[Green Printer]

Ink is a major input variable but it is not controlled properly now. It should be.

I dare any researcher out there to do a proper test of the process and report the results. But they will probably not take up that dare because they want to think that they are already doing science, which they aren't. They are only doing industrial trial and error experimentation.

This is an interesting statement does it have any relationship to the beta testing of the ITB? To me it would appear that anytime a different ink was used for the ITB test the data to be quantified would not have a direct relationship to the previous test.
Were they any test targets in non image areas to see the effect of ink film thickness on dot gain?