Ink densities

Lpool

Member
Hi,

I don't know if someone can help me with this issue. I'm looking for Sun Chemicals ink densities to calibrate my plates for sheetfed printing. Currently we are using SunLit Diamonds DIA 25 Process Cyan, DIA 46 Process Black & Yellow, DIA 27 Process Magenta Inks. It would be greatly appreciated if someone can help me out our guide me.

Many thanks
Andrew
 
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gordo

Well-known member
Hi,

I don't know if someone can help me with this issue. I'm looking for Sun Chemicals ink densities to calibrate my plates for sheetfed printing. Currently we are using SunLit Diamonds DIA 25 Process Cyan, DIA 46 Process Black & Yellow, DIA 27 Process Magenta Inks. It would be greatly appreciated if someone can help me out our guide me.

Many thanks
Andrew

I doubt that Sun Chemical would have ink density targets for their ink.
I guess it depends on what you are trying to do, i.e. what you mean by "calibrate my plates."
Have you tried starting with the old standards?

C 1.40
M 1.50
Y 1.05
K 1.70

They are not specifications though.

best, gordo
 

gordo

Well-known member
If not the company making the ink determining the ideal density then who?

The individual printshop determines the ideal density.

The industry standards organizations like ISO provide examples of typical densities, however, the density values they publish are for information purposes - they are not specifications. There are way too many variables if density is the only target.
Print standards provide specifications for the ink hue measured with your spectrophotometer at the ink densities that allows your press to print in a reliable, relatively consistent, and artifact-free manner.
So, the ink manufacturer might tell you that the ink hue complies with industrial standards like ISO 2846:1 (ink color) and therefore would help you conform to ISO 12647:2 in an offset pressroom - but that's as far as they are likely to go.

best, gordo
 

chevalier

Well-known member
When the ink vendor achieves conformance to ISO 2846:1 shouldn't they designate the density they used to achieve conformance? To my brain it seems like "standard" ink density should be determined based upon the chemical profile of the ink most optimally achieving its target color. ("Most optimally" being a nice and easy way of wrangling many variables into a simple phrase.) With every vendor's inks having different chemical makeups and various amounts of pigment/carrier/catalyst/initiator it just seems fundamental that the ink vendor should be designate the ideal standard density of their inks.

Where am I getting off track here?
 
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gordo

Well-known member
When the ink vendor achieves conformance to ISO 2846:1 shouldn't they designate the density they used to achieve conformance? To my brain it seems like "standard" ink density should be determined based upon the chemical profile of the ink most optimally achieving its target color. ("Most optimally" being a nice and easy way of wrangling many variables into a simple phrase.) With every vendor's inks having different chemical makeups and various amounts of pigment/carrier/catalyst/initiator it just seems fundamental that the ink vendor should be designate the ideal standard density of their inks.

Where am I getting off track here?

Because their press condition and instruments would be different than yours any numbers they could provide would be meaningless and possibly lead to liability issues for them. Also, they would probably say that it is the job of the print standards organizations to provide such guidelines just as they do for dot gains.
In the steam-powered days of the past, organizations like SWOP provided Hi/Lo process ink density samples that the printer could measure with their instrument. Whatever density values the printer's instrument read then became the High and Low density numbers that the printer should be within. Keep in mind that SWOP does not provide specifications for the press room. But for the proofing system. There are no SID targets.

hope that helps, gordo
 

saso777

Active member
I totally agree with gordo and you should try like:
C:1.30-1.140
M:1.40-1.50
Y:1.05-1.10
K:1.70-1.80
 

rich apollo

Well-known member
When the ink vendor achieves conformance to ISO 2846:1 shouldn't they designate the density they used to achieve conformance?

You're also assuming that the inkset in question conforms to 2846. Many inks do not. The conditions for ISO 2846 testing are nothing like offset printing.

The original poster needs to decide what colors he'd like the solids to hit, then determine what densities achieve those targets, then decide if those are densities that can be consistently run.
 

gordo

Well-known member
The original poster needs to decide what colors he'd like the solids to hit, then determine what densities achieve those targets, then decide if those are densities that can be consistently run.

You blinked ;-)

best, gordo
 

chevalier

Well-known member
Because their press condition and instruments would be different than yours any numbers they could provide would be meaningless and possibly lead to liability issues for them. Also, they would probably say that it is the job of the print standards organizations to provide such guidelines just as they do for dot gains.

I'm still not getting it. Perhaps I am misunderstanding something fundamental here. Please educate me here. Here is the longer version of my thinking:

A solid is measured to conform to a certain LAB value and tolerance (such as ISO 2846). If to achieve ISO 2846 conformance with a specific ink a certain density range is going to exist to achieve that LAB value on whatever substrate. Isn't the density to achieve LAB conformance completely independent of the printing process/equipment and unique to that specific ink and substrate? Without this interdependence existing between LAB value and density how can measurement systems calculate density from the LAB value? I understand that density and LAB are not perfectly congruent to each other but they are interdependent at some level right?
 

Kaoticor

Well-known member
I'm still not getting it. Perhaps I am misunderstanding something fundamental here. Please educate me here. Here is the longer version of my thinking:

A solid is measured to conform to a certain LAB value and tolerance (such as ISO 2846). If to achieve ISO 2846 conformance with a specific ink a certain density range is going to exist to achieve that LAB value on whatever substrate. Isn't the density to achieve LAB conformance completely independent of the printing process/equipment and unique to that specific ink and substrate? Without this interdependence existing between LAB value and density how can measurement systems calculate density from the LAB value? I understand that density and LAB are not perfectly congruent to each other but they are interdependent at some level right?

Your reasoning makes sense: In theory there should be a certain amount of ink that you would need to hit you Lab numbers. However, that would probably never match what you will actually need on press. The reason is because each press and each set of printing conditions is different, no matter what you do.

To illustrate: you can make a strong cup of coffee with 2 tablespoons on a cuban coffee maker.
Throw 2 tablespoons of coffee into a 3-minute coffee maker and and it will barely change the color of the water.

In theory, yes, you only need 2 tablespoons of coffee to make a strong cup. But is that going to be true in every place around the world? Now what if Sun Chemical advertised that an ISO compliant yellow could be reached at 1.05 density? That might be true, in theory. But a set number would usually never hold true to get your inks acceptable. Like Gordo stated, there are just way to many variable to set a number on your solids. Putting a set number on your densities was very common in older print shops, but has really become a thing of the past, and attention has shifted to looking at many of the other variables that are understood to be involved nowadays.
 

chevalier

Well-known member
Exactly how does one determine what the standard ink densities should be? Should each press have its own ideal standard ink densities even if it is in the same plant using the same paper, plates, water, ink, etc.? I mean if variability is the issue I can only assume water, ink, roller-train (milling), blankets, etc. are going to keep any vendor (ink, press, paper, etc.) from determining this.
 
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Orpheus42

Member
Putting a set number on your densities was very common in older print shops, but has really become a thing of the past, and attention has shifted to looking at many of the other variables that are understood to be involved nowadays
.

Well I would disagree there, what I would say is that if you specify the ink and the substrate to an ink manufacturer then they should be able to provide you an ink that when you put it on press matches ISO 12647-2 L*a*b* values. Or in other words you match the ink on the substrate to the CIE L*a*b* values and from that you acquire the density values.

Why would that not be achievable on press? (Gordo - is this what you mean by individual matching?)

How else can you try to standardise the process, for in theory you could put a batch of ink on press one day and hit your Lab values at density 'x' and another batch may hit the Lab values at density 'y' but your TVI curves would be out of the window. IMO it is difficult to separate LAB and density completely, but density is the dependent variable.
 

michaelejahn

Well-known member
This 'might' help.

This 'might' help.

Exactly how does one determine what the standard ink densities should be?

You don't / they don't / we don't.

DEER Printing Guidelines 2011 Poster-DOWNLOAD | IDEAlliance

Take a moment to download and examine this poster. I am not here to waste time with deep debates on the G7 method's validity or ecosystem. I am afraid that you may have to re-think a fundamental concept - there is no ideal or targeted 'standard' ink density, no more than there are standard unicorn horn lengths..

No trying to be mean spirited here, but several folks have tried to gently point this out and you keep asking that same question. Even if you hate everything G7 and have no interest in joining that cult, the very bottom of the DEER poster - Pressroom charts the ISO-standard inks and substrates and the G7 print control metrics for various print specifications - it might at least calm the hornets in brain related to your strong pursuit of the mythical standard ink density.

I am no G7 expert, but I have several close friends that are, and I still am friends with then, in spite of that.

( wink )

Hope this helps in some way. You may need to at least SIP the kool-aid.
 

chevalier

Well-known member
You don't / they don't / we don't.

DEER Printing Guidelines 2011 Poster-DOWNLOAD | IDEAlliance

Take a moment to download and examine this poster. I am not here to waste time with deep debates on the G7 method's validity or ecosystem. I am afraid that you may have to re-think a fundamental concept - there is no ideal or targeted 'standard' ink density, no more than there are standard unicorn horn lengths..

No trying to be mean spirited here, but several folks have tried to gently point this out and you keep asking that same question. Even if you hate everything G7 and have no interest in joining that cult, the very bottom of the DEER poster - Pressroom charts the ISO-standard inks and substrates and the G7 print control metrics for various print specifications - it might at least calm the hornets in brain related to your strong pursuit of the mythical standard ink density.

I am no G7 expert, but I have several close friends that are, and I still am friends with then, in spite of that.

( wink )

Hope this helps in some way. You may need to at least SIP the kool-aid.

It appears you are misunderstanding this whole conversation. Your smart*** remarks are unnecessary and not appreciated. I already use the G7 process and I have complete faith in it. You are making major assumptions here that are completely false.

Density is important in consistency and as a launching point to hit LAB targets yet somehow this is not getting clearly communicated. The updated DEER poster has now made this clear to me.

Pressroom heading, Step 3
To find YOUR target solid ink densities, first achieve the closest solid Lab values possible, then switch the instrument to density and record your particular values.

This is exactly what my last post was suggesting. The SIDs should be determined at each press after the calibration then recorded for normal press operation. It has been my experience both preG7 and postG7 introduction that when presses are installed and/or curves are calculated that the vendor asks the press operators "what are your standard ink densities?". This question obviously shouldn't be asked as this should be determined by results of hitting the desired LAB target values.
 

michaelejahn

Well-known member
Apologies all around, shots for everyone at the bar !

Apologies all around, shots for everyone at the bar !

It appears you are misunderstanding this whole conversation. Your smart*** remarks are unnecessary and not appreciated. I already use the G7 process and I have complete faith in it. You are making major assumptions here that are completely false.

I already stated that I was not being mean spirited. To know me is to love me. You don't know me. That is okay, others appreciate my weird snarky replies.

oddly - what I shared did seem to help you in some small way since you then wrote;

Density is important in consistency and as a launching point to hit LAB targets yet somehow this is not getting clearly communicated. The updated DEER poster has now made this clear to me. .

When I read your earlier posts, I was convinced at once that you did not grasp the fundamentals of what G7 was all about. That assumption was incorrect. I apologize.

So - this part ( below ) is indeed the crux of the problem, and shows we ( as an industry ) have made some progress here, but old ideas take a long time to die ...

It has been my experience both preG7 and postG7 introduction that when presses are installed and/or curves are calculated that the vendor asks the press operators "what are your standard ink densities?". This question obviously shouldn't be asked as this should be determined by results of hitting the desired LAB target values.


I think that is exactly the case. A G7 expert often feels like they were invited to help a team play ice hockey better --- and when they show up, everyone is wearing football gear.

Densitometer wielding press operators sometimes do not get on well with or understand the options available in the prepress area, nor to they show big love and understanding with Spectrophotometer Specialist types. This is a mindset change, and perhaps that was all I was trying to suggest in my "G7 baseball bat across the forehead" way.

Just keeping the "Laugh" in the L part of Lab here.

I think that DEER poster is awesome, and ofte just share that bottom part as an image;

http://support.composeusa.com/webfiles/DeerPressroom.png

I have that image laminated onto a Louisville slugger. Maybe you might make use of it in your environment.

Best of luck - and I wish this were all so simple. There are also folks using DeviceLink profiles where they make device dependent PDF files that move that process so far upstream who WISH it were as simple as "please run your inks at these densities" - in the digital inkjet world, it sure seems to work well.
 

gordo

Well-known member
The SIDs should be determined at each press after the calibration then recorded for normal press operation. It has been my experience both preG7 and postG7 introduction that when presses are installed and/or curves are calculated that the vendor asks the press operators "what are your standard ink densities?". This question obviously shouldn't be asked as this should be determined by results of hitting the desired LAB target values.

This is where I would disagree with G7.
IMHO solid ink density and Lab values serve different functions and should used accordingly.

The function of a printing press is to lay down a film of ink that is as close a facsimile of the halftone dot on the plate as possible. This is a mechanical function. SIDs are an indirect measurement of the thickness of that film of ink. So SIDs are important to the press operator for that reason.
Presses do not make color. SIDs do not measure color.

Color comes from the ink hue and its relationship with light. Spectrodensitomers measure light and report the hue as a Lab value. This is a perceptual function. The press operator has very little control over the Lab values since they are determined by the choice of ink hue, substrate, and lighting over which the press operator has little control.
I don't think that you can say one is more important than the other because they are separate, albeit related, metrics.
At the end of the day the goal is to align presswork color to the proof. Lab value information can help achieve that goal.

It is reasonable for the vendor to ask the press operators "what are your standard ink densities?" because the answer can provide an insight into problems between prepress and pressroom as well as general print manufacturing and process control deficiencies.

The problem in this industry is that standards like ISO 12647 are very poorly written and the specifications are often ambiguous, or useless as a means to implementation. There is also a general lack of clear information about how the process works.

There is also a problem with using numbers whether they are SID or Lab values. Numbers have a certain sense of absoluteness about them. For example, the number 4 is unambiguous and specific. The number 4.3 is even more unambiguous and specific. However if an instrument says that there is a delta E of 4.3 between two colors or that the SID should be 1.43 - those numbers may not be meaningful. For example, here is a chart showing the difference in reported Lab values for seven different spectrophotometers measuring the same color patches on 80lb gloss paper. Each color bar represents a specific instrument (i.e. all green bars are one instrument - all red bars another).



In this case there is a delta E as great as 7 between some of these instruments. Even with the same instrument there is a delta difference based on the color that's being measured.

Instruments do not agree - even from the same manufacturer. Different instruments do not report the same values (density or Lab) from measured samples. So you have to be very careful when quoting those values. They provide guidance but they are not absolute.

best, gordo
 

Lukas Engqvist

Well-known member
This is why the proof and print ought to be measured with the same instrument if possible. Are the instruments different manufacturers and or models.
 

chevalier

Well-known member
I completely agree about color measurement devices. I was attempting to comprehend the purpose and actual usefulness of SID in a LAB world. It seems that the conclusion is that SID seems to be a necessary evil as a launching point. Is that a fair point?
 

Kaoticor

Well-known member
.

Well I would disagree there, what I would say is that if you specify the ink and the substrate to an ink manufacturer then they should be able to provide you an ink that when you put it on press matches ISO 12647-2 L*a*b* values. Or in other words you match the ink on the substrate to the CIE L*a*b* values and from that you acquire the density values.

Why would that not be achievable on press? (Gordo - is this what you mean by individual matching?)

How else can you try to standardise the process, for in theory you could put a batch of ink on press one day and hit your Lab values at density 'x' and another batch may hit the Lab values at density 'y' but your TVI curves would be out of the window. IMO it is difficult to separate LAB and density completely, but density is the dependent variable.

I think you might be talking about a different discussion ;) . It is not the ability of the ink to hit the ISO targets that is in question, or the print shop running at a density that lines everything up at their place. It is specifying a set number, regardless of print shop. As the chart above shows, it just cant be done. While the number is definitely a usefull tool on press, and for the print shop itself, a specific value for density is just not something that can be specified by the ink manufacturer.
 

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